Project Evaluation - The Operation of the Project and Process Evaluation

Project Evaluation - The Operation of the Project and Process Evaluation

Relevant TPOs

M8 Baillieston to Newhouse

• To support sustainable economic activity and get good value for money, in particular;
  • to reduce delay and travel time reliability for all traffic, including goods vehicles and buses, in the A8 corridor.

A725 Raith Junction

• Provide free flow for A725 traffic
• Relieve traffic congestion at the junction

M8 / M73 / M74 Associated Network Improvements

• Relieve traffic congestion
• Optimise benefits of the M8 Baillieston to Newhouse works by improving east - west traffic movement between the M8 and M74
• Integrate benefits realised from other works such as the M74 completion and the M80 Stepps to Haggs scheme.

Network Traffic

The evaluation is supported by the consideration of pre and post-opening comparisons of operational indicators, which focuses on network traffic indicators including traffic volumes, travel times and vehicle speeds, presented in the following section. Further operational indicators, including Intelligent Transport System (ITS) impacts and post-opening queue conditions, at specific locations on the local road network, are also discussed.

Background Traffic Growth

Scottish Transport Statistics No. 38: 2019 Edition presents details of growth in traffic across the trunk road network by local authority area. The growth in traffic on trunk roads (in the form of million vehicle kilometres) between 2008 and 2018 across the City of Glasgow, North Lanarkshire Council (NLC) and South Lanarkshire Council (SLC) areas (within which the project is located) is presented in Figure 10.

This data is presented alongside the growth from the neighbouring local authorities of Falkirk, West Lothian and City of Edinburgh Councils, for comparative purposes. These statistics are included to put the traffic growth trends within the area in which the project is located into the context of prevailing trends in traffic growth across the wider Scottish Trunk Road Network.

The indexed trends presented in Figure 10 indicate that, from the data presented in the latest Scottish Transport Statistics publication, growth in the recorded vehicle kilometres on trunk roads within the City of Glasgow and SLC’s boundaries are slightly greater than that recorded across the trunk road network as a whole. While growth over the period 2008 to 2011 was muted, likely as a direct result of the wider economic downturn in 2008 and 2009, between 2011 and 2018, growth in trunk road vehicle kilometres across the Glasgow City, SLC and NLC areas totalled approximately 17%. This can be compared to growth across the entire Scottish trunk road network of approximately 15%. This suggests that traffic growth locally may have been somewhat greater than the growth observed across the trunk road as a whole.

Data surrounding growth in trunk road vehicle kilometres within the NLC area appears skewed through the period 2012 to 2015. The reasons for the significant increase in vehicle kilometres cannot be confirmed, however, may be related to the opening of the M80 Stepps to Haggs project in 2011. Disregarding the data over this period, the general trend over the period 2011 to 2018, however, is one of growth (of around 15%) which is broadly comparable with the growth observed on the trunk road nationally.

It can be deduced that the available data suggests annual average growth, in recorded vehicle kilometres on trunk roads within Glasgow City, SLC and NLC areas, over the 7-year period 2011 to 2018, of around 2.5%. This compares with the national figure over the same period, of around 2.1%, suggesting growth has been greater within the vicinity of the study area, compared to across the trunk road network, as a whole.

Traffic Volumes

Transport Scotland’s National Traffic Data System (NTDS) contains records of traffic count data across the Scottish trunk road network, including data covering the routes upgraded as part of the project. The locations of the Automatic Traffic Counters (ATCs) used to record traffic flows within the study area are shown in Figure 11 and are listed below:

1. M8 West of Junction 9

2. M8 West of Junction 8

3. M73 North of M8

4. A8 East of Junction 8

5. A8 West of Junction 7

6. M8 East of Junction 7

7. M8 West of Junction 6

8. M8 East of Junction 6

9. M73 South of M8

10. A725 South of M8

11. A725 North of M74

12. M74 East of Junction 3

13. M74 West of Junction 3A

14. M74 South of Junction 4

15. M74 West of Junction 5

16. A725 South of M74

17. M74 South of J5

18. M74 South of Junction 6

19. M73 to M8 Slip Road

20. M8 to M73 Slip Road

21. M8 Off-slip at J8

22. M8 On-Slip at J8

23. M74 to M73 Slip Road

24. M73 to M74

25. A725 to M8 Slip Road

26. M8 to A725 Slip Road

27. A725 South of M74

28. M8 East of J8

29. M8 West of J7

30. M8 West of J10

A record of the NTDS counters included within the evaluation, and the specific references of the traffic counters from which data has been obtained and used, is presented in Appendix B.

Comparison Between Pre and Post-Opening Traffic Flows

The available NTDS data has been obtained and analysed to inform the 1YA Evaluation. In defining the project’s evaluation period, cognisance of other major trunk road network improvements has been made. A timeline, presenting the construction phases of the major motorway improvement projects completed within Central Scotland over the past decade, the impacts of which could influence network operating conditions either within the vicinity of, or on the routes upgraded as part of the M8 M73 M74 Motorway Improvements Project, is presented in Figure 12.

M74 Construction 2010/11 Q1 to Q4. M80 Stepps to Haggs Construction 2010/11 Q1 to 2011/12 Q2, snagging 2011/12 Q2 to 2012/13 Q1.

Based on the information presented in Figure 12, it can be seen that the M74 Completion and M80 Stepps to Haggs projects were opened to traffic in quarter one and quarter two of the 2011/12 financial year respectively. On this basis, pre and post-opening comparisons of traffic volumes on the routes upgraded as part of the project, are based on data from the following periods:

• Pre-Opening – January 2011 to December 2013
• Post-Opening – September to November 2019

Pre and post-opening traffic flow impacts are normally evaluated on the basis of multiple years of traffic data (in order to give more confidence in the results presented) and as a minimum at least one complete year of data would be used. In the case of the M8 M73 M74 Motorway Improvements Project, however, this has not been possible. This is due to issues with the installation and operation of traffic counters following opening of the project. As such, the available data (from September to November 2019) has been used to define post-opening conditions as part of the 1YA Evaluation. The pre-opening period selected avoids (as far as is practical) the impacts of construction work associated with the M80 Stepps to Haggs project and the associated impact on traffic flows / patterns.

To put into context the varying average daily traffic volumes over the periods used as the basis of the comparisons presented within the 1YA Evaluation, a summary and comparison of the available traffic data is presented. The average daily flows through January to December, the AADT flow across the period examined, the average daily flow across neutral months and the average daily flow over the September to November period, for a selection of counters across the network during the pre-opening period, are presented in Figure 13 (neutral months, in the context of traffic flows in Scotland, include March, April, May, October & November).

Based on the information presented in Figure 13, it can be seen that average daily traffic flows over the period September to November are slightly greater than both the annual average daily traffic volume and the ‘neutral period’ average daily traffic volume (by approximately 6% and 4% respectively). On this basis, the comparison of pre and post-opening traffic volumes undertaken within the 1YA Evaluation will be based on traffic flows recorded within the September to November period only, to ensure traffic volumes are compared on a like-for-like basis.

The project can be defined in terms of three discrete sections: the M8 Corridor, the A725 Corridor and the M73 / M74 Corridor. Impacts, in terms of changes in traffic flows on the upgraded network, are described in the following report sections.

M8 Corridor

The M8 Corridor, for the purposes of the evaluation of pre and post-opening traffic volumes, is broadly defined as the M8 between Junction 11 Stepps, in the west, to Junction 5 Harthill, in the east. It includes the A8 APR constructed as part of the project between Swinton Roundabout, in the west, and Junction 6 Newhouse, in the east.

The AADT flows pre and post-opening of the project, within the M8 Corridor, are presented in Figure 14.

As can be seen from the traffic flow data presented in Figure 14, post-opening daily traffic volumes are somewhat greater when compared to pre-opening levels within the M8 Corridor, between Junction 8 Baillieston and Junction 6 Newhouse. Post-opening increases of up to around 27,000 vpd (up to 34%) were observed based on the data available at the time of the 1YA Evaluation. The larger increase observed between Junction 7a Shawhead and Junction 7 Eurocentral may point to the importance of the Eurocentral site as a major employment and goods distribution destination within the wider area and suggests a significant volume of traffic may be accessing the site via the A725.

Within the corridor, more generally, the M8 carried between approximately 49,000 and 85,000 vpd, with the A8 APR carrying between approximately 14,000 and 21,000 vpd. This goes to highlight the continued importance of the A8 APR as a key route within the study area.

On the M8, to the west of Junction 8 Baillieston, pre and post-opening traffic volumes are broadly comparable, suggesting strategic traffic volume on this section of the road network may have stabilised. To the east of Junction 6 Newhouse, post-opening traffic volumes were somewhat lower than pre-opening levels, in the order of 6,000 vpd (11%).

This suggests, on the basis of the limited post-opening traffic data available at the time of the 1YA Evaluation, traffic volumes on the M8, to the east of the study area i.e. strategic east – west trips, may have reduced following opening of the project. Longer term trends in traffic volume changes will be reviewed as part of subsequent evaluations for the project, when post-opening data covering a longer time period should be available.

The motorway network upgraded as part of the project plays an important role in facilitating commuting traffic within the wider Central Scotland region. As such, it is also important to understand the project’s impact on traffic volumes across discreet periods of the day. Pre and post-opening traffic flows within the AM, Inter Peak (IP) and PM periods, therefore, have been examined. For the purposes of the evaluation, these periods have been defined as follows:

• AM Period – 07:00 – 10:00
• IP Period – 11:00 – 14:00
• PM Period – 16:00 – 19:00

An ‘average hour’ within each of the three periods has been calculated, for comparative purposes. The comparison of pre and post-opening traffic volumes, by time period, are presented in Figure 15, Figure 16 and Figure 17.

As can be seen from the information presented in Figure 15, Figure 16 and Figure 17, traffic volumes within the M8 Corridor, across each of the AM, IP and PM Periods have increased significantly compared with pre-opening levels. In summary, post-opening traffic volumes are:

• Between 100 and 2,000 greater when compared to pre-opening levels, during the AM period
• Between 300 and 1,500 greater when compared to pre-opening levels, during the IP period
• Between 300 and 2,500 greater when compared to pre-opening levels, during the PM period

Whilst cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, it can be judged that improvements in the reliability of journey times within the M8 Corridor has played a part in increasing the overall volume of traffic using the M8 and A8 APR.

Given the changes in peak period traffic flows discussed above, resulting from reductions in queuing and congestion during the most heavily trafficked periods of the day, it can be expected that this may have a subsequent impact on driver behaviour, specifically relating to the timing of journeys i.e. when they are made. This is likely to occur predominantly during the AM and PM peak periods, where individuals commuting to and from various area of North Lanarkshire (e.g. Airdrie, Holytown and Bellshill) to work in Glasgow, hauliers delivering goods and those making strategic east – west trips between Glasgow, Edinburgh and beyond may identify opportunities to re-time journeys to account for the more reliable journey times during these periods.

In order to understand changes in the timings of journeys made within the M8 / A8 Corridor, the average weekday daily profile of traffic on the M8, in the eastbound and westbound directions of travel, have been examined. Each direction has been examined separately to account for the tidal nature of traffic. The specific locations used are as follows:

• M8 Eastbound, West of Junction 6 Newhouse
• M8 Westbound, East of Junction 8 Baillieston

The comparison of pre and post-opening average weekday daily traffic profiles on the M8, in the eastbound and westbound directions of travel respectively, are presented in Figure 18 and Figure 19.

Based on the pre and post-opening daily traffic flow profiles presented in Figure 18 and Figure 19, it can be deduced that:

• During the AM period, a greater proportion of daily trips are undertaken in the westbound direction of travel, between the hours of 06:00 and 10:00 and in the eastbound direction of travel, between the hours of 05:00 to 07:00
• During the PM period, a lower proportion of daily trips are undertaken, in the eastbound direction of travel, between the hours of 16:00 and 19:00. There is no discernible change in the proportion of trips in the westbound direction of travel.

The greater proportion of daily trips travelling on the M8, in the westbound direction (towards Glasgow) during the AM period, is likely to be as a direct result of commuters seeing the benefits of reduced congestion on the road network and re-timing journeys accordingly. There may also be an element of induced demand during this period, with those previously unable or unwilling to travel during this period now able or willing to do so, due to the more reliable nature of journey times and reduced congestion on the road network.

The greater proportion of trips in the eastbound direction of travel in the early AM period may be as a result of congestion issues elsewhere on the trunk road network i.e. towards Edinburgh. A proportion of commuters travelling to the east may be commencing their journeys earlier in the morning, to avoid congestion issues on the M8 towards Edinburgh, or on the A720 Edinburgh City Bypass. It is outwith the scope of the 1YA Evaluation, however, to evaluate operational issues on the road network outwith the evaluation study area, and their subsequent impact on traffic conditions within the vicinity of the project.

Transport Scotland will continue to liaise with its local authority and operating company partners to identify, assess and mitigate operational constraints on the trunk road network, through targeted interventions, major infrastructure projects or influencing shifts in travel behaviour.

A725 Corridor

The A725 Corridor, for the purposes of the evaluation of pre and post-opening traffic volumes, is broadly defined as the A725 between Whistleberry Junction, south of Raith Junction to the merge with the M8 Junction 7a Shawhead.

The AADT flows pre and post-opening of the project, within the A725 Corridor, are presented in Figure 20.

As can be seen from the traffic flow data presented in Figure 20, post-opening traffic volumes within the A725 Corridor have increased significantly compared with pre-opening levels. In summary, post-opening traffic volumes are:

• Around 13,700 greater south of Raith Junction (directly to the south of the M74) when compared to pre-opening levels,
• Approximately 12,900 greater north of Raith Junction (directly to the north of the M74) when compared to pre-opening levels,
• Around 11,300 greater north of Bellziehill Junction, when compared to pre-opening levels,

As previously noted, whilst cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, it can be judged that the significant reduction in the congestion and delays previously inherent within the A725 Corridor has played a part in significantly increasing the volume of traffic using the route.

As a result, the A725, when considered as part of a wider route, including the A726 Glasgow Southern Orbital (GSO) from M77 Junction 5 to East Kilbride, is now better able to perform its role as a strategic transport corridor. This route links the M77 and M8 motorways, providing an alternative strategic route for traffic to and from Ayrshire and the south-west to Edinburgh and the east / north east of Scotland.

Pre and post-opening traffic flows within the AM, IP and PM periods have also been examined and are presented in Figure 21, Figure 22 and Figure 23.

As can be seen from the information presented in Figure 21, Figure 22 and Figure 23, post-opening traffic volumes within the A725 Corridor, across each of the AM, IP and PM Periods have increased significantly compared with pre-opening levels. In summary, post-opening traffic volumes are:

• Between 1,000 and 2,000 greater when compared to pre-opening levels, during the AM period
• Between 600 and 1,000 greater when compared to pre-opening levels, during the IP period
• Between 1,100 and 1,900 greater when compared to pre-opening levels, during the PM period

As previously noted, whilst cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, it can be judged that the significant reduction in the congestion and delays previously inherent within the A725 Corridor has played a part in increasing the volume of traffic using the route.

Given the changes in peak period traffic flows discussed above, resulting from reductions in queuing and congestion during the most heavily trafficked periods of the day, it can be expected that this may have a subsequent impact on driver behaviour, specifically relating to the timing of journeys i.e. when they are made. This is likely to occur predominantly during the AM and PM peak periods, where individuals commuting to and from various area of North and South Lanarkshire (e.g. East Kilbride, Hamilton, Bellshill and Coatbridge) to work in Edinburgh and hauliers delivering goods may identify opportunities to re-time journeys to account for the more reliable journey times during these periods.

In order to understand changes in the timings of journeys made within the A725 Corridor, the average weekday daily profile of traffic on the A725, in the northbound and southbound directions of travel, have been examined. Each direction has been examined separately to account for the tidal nature of traffic. The specific locations used are as follows:

• A725 Northbound, South of Raith
• A725 Southbound, North of Raith

The comparison of pre and post-opening average weekday daily traffic profiles on the A725, in the northbound and southbound directions of travel respectively, are presented in Figure 24 and Figure 25.

Based on the pre and post-opening daily traffic flow profiles presented in Figure 24 and Figure 25, it can be deduced that:

• During the AM period, a slightly greater proportion of daily trips are undertaken in the northbound direction of travel, between the hours of 06:00 and 10:00 and a significantly greater proportion of daily trips in the southbound direction of travel, between the hours of 06:00 and 11:00
• During the PM period, a greater proportion of daily trips are undertaken, in the northbound and southbound directions of travel, between the hours of 16:00 and 18:00.

The greater proportion of daily trips travelling on the A725, in both the northbound and southbound directions during the AM period, is likely to be as a direct result of commuters seeing the benefits of reduced congestion due to the grade-separation of the junction at Raith and are re-timing journeys accordingly. There is likely also to be the combined effect of changes in traffic patterns within the wider network (motorists rerouting onto the A725 from other local routes, due to the increased reliability of journey times) in addition to an element of induced demand during this period. Individuals previously unable or unwilling to travel during this period may now be able or willing to do so, due to the more reliable nature of journey times and reduced congestion on the road network.

This is mirrored during the PM period, albeit at a lower level. The reduction in the proportion of daily trips, primarily in the southbound direction of travel, over the period 18:00 to 20:00 suggests that journeys are now being made during the peak period of travel i.e. between 16:00 and 18:00, due to the more reliable nature of journey times following grade separation of the Raith Junction.

M73 / M74 Corridor

The M73 / M74 Corridor, for the purposes of the evaluation of pre and post-opening traffic volumes, is broadly defined as the M74 between Junction 7 Larkhall, in the south, to Junction 3 Carmyle, in the north. Additionally, it includes the M73 between Junction 1 Maryville to Junction 2a Gartcosh.

The AADT flows pre and post-opening of the project, within the M73 / M74 Corridor, are presented in Figure 26.

As can be seen from the traffic flow data presented in Figure 26, post-opening traffic volumes within the M73 / M74 Corridor have increased significantly compared with pre-opening levels. In summary, post-opening traffic volumes are:

• Around 8,000 vpd greater on the M74 between Junction 5 Raith and Junction 6 Hamilton, when compared to pre-opening levels
• Around 14,000 to 23,000 vpd greater on the M74 between Junction 5 Raith and Junction 3A Daldowie, when compared to pre-opening levels
• Around 20,000 vpd greater on the M74 between Junction 3A Daldowie and Junction 3 Carmyle (north of the project extents), when compared to pre-opening levels
• Around 7,000 vpd greater on the M74 between Junction 6 Hamilton and Junction 7 Larkhall (south of the project extents), when compared to pre-opening levels
• Between approximately 10,000 and 11,000 vpd greater on the M73, to the north and south of Junction 2 Baillieston respectively, when compared to pre-opening levels

As previously noted, whilst cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, it can be judged that improvements in the reliability of journey times within the M73 / M74 Corridor has played a part in increasing the volume of traffic using the route.

Pre and post-opening traffic flows within the AM, IP and PM periods have also been examined and are presented in Figure 27, Figure 28 and Figure 29.

As can be seen from the information presented in Figure 27, Figure 28 and Figure 29, traffic volumes within the M73 / M74 Corridor, across each of the AM, IP and PM Periods have increased significantly compared with pre-opening levels.

In summary, post-opening traffic volumes are somewhat greater when compared to pre-opening levels within the M73 / M74 Corridor, on the M73 between Junction 2a Gartcosh and Junction 1 Maryville and on the M74 between Junction 7 Larkhall and Junction 3 Carmyle. Post-opening increases on the M74 of up to around 1,400 to 2,000 in the AM and PM periods respectively were observed based on the data available at the time of the 1YA Evaluation. On the M73, south of Junction 2 Baillieston, post-opening increases of up to around 700 to 1,200 were observed, in the AM and PM periods respectively.

As previously noted, whilst cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, it can be judged that improvements in the reliability of journey times within the M73 / M74 Corridor has played a part in increasing the volume of traffic using the route.

Given the changes in peak period traffic flows discussed above, resulting from reductions in queuing and congestion during the most heavily trafficked periods of the day, it can be expected that this may have a subsequent impact on driver behaviour, specifically relating to the timing of journeys i.e. when they are made. This is likely to occur predominantly during the AM and PM peak periods, where individuals commuting to and from various area of North and South Lanarkshire (e.g. Motherwell, Wishaw, Stonehouse, Larkhall and Hamilton) to work in Glasgow, hauliers delivering goods and those making strategic north – south trips between the Central Belt, the South of Scotland and beyond may identify opportunities to re-time journeys to account for the more reliable journey times during these periods.

In order to understand changes in the timings of journeys made within the M73 / M74 Corridor, the average weekday daily profile of traffic on the M74, in the northbound and southbound directions of travel, and on the M73 in the southbound direction of travel, have been examined. Each direction has been examined separately to account for the tidal nature of traffic. The specific locations used are as follows:

• M74 Northbound, South of Junction 4 Maryville
• M74 Southbound, North of Junction 6 Hamilton
• M73 Southbound, North of Junction 1 Maryville

The comparison of pre and post-opening average weekday daily traffic profiles on the M73 and M74, in the northbound and southbound directions of travel respectively, are presented in Figure 30, Figure 31 and Figure 32.

Based on the pre and post-opening daily traffic profiles presented in Figure 30, Figure 31 and Figure 32, it can be deduced that:

• During the AM period, a slightly greater proportion of daily trips are undertaken in the northbound direction of travel on the M74 between the hours of 06:00 and 08:00 and the southbound direction of travel on the M73 between the hours of 06:00 and 09:00. There is no discernible change on the M74 southbound over the same period
• During the PM period, a slightly greater proportion of daily trips are undertaken in the northbound direction of travel on the M74 between the hours of 16:00 and 18:00 and the southbound direction of travel on the M73 between the hours of 16:00 and 18:00. There is no discernible change on the M74 southbound over the same period

The greater proportion of daily trips travelling on the M74, in the northbound direction during the AM period, is likely to be as a direct result of commuters seeing the benefits of reduced congestion and are re-timing journeys accordingly. There is likely also to be an element of induced demand during this period with individuals who were previously unable or unwilling to travel during this period now be able or willing to do so, due to the more reliable nature of journey times and reduced congestion on the road network.

On the M73, in the southbound direction during the AM period, the greater proportion of daily trips is likely as a result of the combined effect of reduced congestion and the re-timing journeys, in addition to a change in traffic patterns on this route. Traffic previously travelling on the M8 to or through Glasgow may be rerouting from the M8 at Baillieston and onto the M74 northbound, via the M73, thus avoiding the need to travel via the Kingston Bridge. This change is mirrored during the PM period.

Summary

Based on the evaluation of pre and post-opening traffic volumes it can be deduced that traffic volumes on large parts of the motorway network upgraded as part of the project are significantly greater post-opening when compared to pre-opening traffic levels. Post-opening AADT volumes within the M8 Corridor, between Baillieston and Newhouse, are up to around 27,000 vpd greater than pre-opening levels. Similar increases are observed on the M74 (post-opening volumes up to approximately 23,000 vpd greater than pre-opening levels) and on the M73 (post-opening volumes up to around 11,000 vpd greater than pre-opening levels). Significant increases have also been observed within the A725 Corridor, with up to an additional 13,700 vpd using the A725 to the south of Raith Junction.

Cognisance of the fact that the comparison of pre and post-opening traffic volumes covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period, should be made when interpreting changes in pre and post-opening traffic volumes. It can be judged that reductions in queuing and congestion and improvements in the reliability of journey times across the study area may have played a part in increasing the volume of traffic using the road network, particularly in specific locations / on certain routes.

Given the length of the project’s construction phase and the limited availability of post-opening traffic count information on the upgraded road network at the time of the 1YA Evaluation, it is not possible, however, to quantify any ‘step-change’ in traffic volumes resulting from the improvements. Instead, traffic growth over the evaluation period i.e. 2011 to 2019 has been reviewed, to put into context localised changes in traffic volumes whilst taking cognisance of the effect of background traffic growth.

A graphical representation of the annual average percentage changes in AADT traffic volumes across the upgraded network, over the seven-year period 2011 to 2019 inclusive, are presented in Figure 33.

As can be seen from the information presented in Figure 33, AADT volumes across the upgraded network have, generally, increased by up to 5% per annum. More significant changes have been observed within the A725 Corridor, likely as a direct impact of the significant reduction in queuing and delays and improvement in journey time reliability resulting from the grade-separation of the Raith Junction. Growth in traffic on the M73, between Junction 1 Maryville and Junction 2 Baillieston, result from reductions in congestion and improvement in the reliability of journey times resulting from the project. This has led to changes in traffic patterns across the wider network, with traffic re previously travelling on the M8, to or through Glasgow, rerouting from the M8 at Baillieston and onto the M74 north of Maryville, via the M73, thus avoiding the need to travel via the Kingston Bridge. Traffic growth within the M8 Corridor, outwith the extents of the project, appears more muted, potentially suggesting that growth in strategic traffic volumes have stabilised.

Comparison Between Predicted and Actual Traffic Flows

Comparisons of the traffic flows predicted as part of the project’s assessment process (commonly referred to as traffic forecasts) with actual observed traffic flow data following opening are undertaken to understand the accuracy of the traffic flow forecasts.

The latest flow comparisons for the project are based on average daily flows from the period September to November 2019 inclusive. As detailed in The Operation of the Project and Process Evaluation section, due to issues with the installation and operation of traffic counters following opening of the project, this is the most suitable post-opening traffic data available from Transport Scotland’s traffic counters within the vicinity of the project, at the time of the 1YA Evaluation. Predicted (forecast) traffic volumes, for 2019, have been derived by interpolating between the available modelled traffic data (from the 2017 and 2022 forecast years) developed to support the project’s assessment.

A comparison of predicted (forecast) and actual traffic volumes is presented in Figure 34.

Based on the comparison of predicted (forecast) and actual traffic volumes, presented in Figure 34, it can be summarised that:

• Actual traffic volumes are between 2% lower and 8% greater than predicted, within the M8 Corridor
• Actual traffic volumes are between 5% and 15% greater than predicted, within the A725 Corridor
• Actual traffic volumes are between 7% and 17% lower than predicted, within the M73 / M74 Corridor

On this basis, it can be deduced that the traffic volumes predicted by the traffic model, developed to support the project’s assessment, are broadly accurate, and well within the acceptable thresholds (+ / - 20%). Whilst there has been a slight overestimation of the volume of traffic using the M8 and A725 Corridors within the traffic model, and an underestimation of traffic using the M73 / M74 Corridor, the magnitude of the variance is such that it is unlikely to have significantly impacted the project’s assessment.

Traffic Volumes: Key Findings

Cognisance of the limited availability of post-opening traffic count information on the upgraded road network at the time of the 1YA Evaluation should be taken when interpreting the comparison of pre and post-opening traffic volumes. Based on the limited information available - pre and post-opening comparisons are based on traffic flows recorded within the September to November period in 2011 to 2013 (pre-opening) and 2019 (post-opening) only, to ensure traffic volumes are compared on a like-for-like basis - it is considered that traffic volumes across the upgraded road network have generally increased (in some locations significantly) following opening of the project.

Post-opening AADT volumes within the M8 Corridor (between Baillieston and Newhouse) are up to around 27,000 vpd greater than pre-opening levels. Similar increases are observed on the M74 (post-opening volumes up to approximately 23,000 vpd greater than pre-opening levels) and on the M73 (post-opening volumes up to around 11,000 vpd greater than pre-opening levels). Significant increases have also been observed within the A725 Corridor, with an additional 13,700 vpd using the A725 to the south of Raith Junction.

Cognisance of the timescales for the comparison of pre and post-opening traffic volumes should be taken. This covers a period of five to seven years (between 2011 / 2013 and 2019) with an element of background traffic growth to be expected over this period. It is considered that the reductions observed in queuing and congestion and improvements in the reliability of journey times across the study area following opening of the project has played a part in increasing the volume of traffic using the road network, particularly in specific locations / on certain routes.

Given the length of the project’s construction phase and the limited availability of post-opening traffic count information on the upgraded road network at the time of the 1YA Evaluation, it is not possible to quantify any ‘step-change’ in traffic volumes resulting from the improvements. A review of traffic growth over the evaluation period i.e. 2011 to 2019, however, indicates that AADT volumes across the upgraded network have, generally, increased by up to 5% per annum. More significant changes have been observed in certain locations i.e. within the A725 Corridor. Traffic growth within the M8 Corridor, outwith the extents of the project, appears more muted, potentially suggesting that growth in strategic traffic volumes have stabilised.

The traffic volumes predicted by the traffic model, developed to support the project’s assessment, are broadly accurate, and well within the acceptable thresholds (+ / - 20%). Whilst there has been a slight overestimation of the volume of traffic using the M8 and A725 Corridors within the traffic model (up to 8% and 15% greater than observed, respectively), and an underestimation of traffic using the M73 / M74 Corridor (up to 17% lower than observed) the magnitude of the variance is such that it is unlikely to have significantly impacted the project’s assessment.

Travel Times

Comparison Between Pre & Post-Opening Travel Times

In order to support the project’s evaluation, an extensive programme of journey time surveys have been undertaken. The project was anticipated to result in significant travel time savings for strategic traffic across the upgraded network. These strategic movements are presented graphically in Figure 35 and described below:

• M8 J10 Bartiebeith to M8 J6 Newhouse
• M73 at M74 J4 Maryville to M73 J2a Gartcosh
• M74 J3 Carmyle to M74 J6 Hamilton
• A725 at M8 J7a Shawhead to A725 in vicinity of A724

Pre-opening journey time surveys were carried out as part of the project’s appraisal in March 2012. A further set of pre-opening journey time surveys were undertaken in April / May 2014 to provide a suitable baseline for the project’s evaluation. Post-opening journey time surveys were carried out to support the 1YA Evaluation in July & August 2017, June 2019 and October & November 2019 to provide an indication of the changes in average journey times resulting from the upgraded network. To capture the varying durations of journeys across the day, traffic surveys were undertaken within the following survey periods:

• AM Survey Period – 07:00 – 10:00
• IP Survey Period – 11:00 – 14:00
• PM Survey Period – 16:00 – 19:00

The project can be defined in terms of three discrete sections: the M8 Corridor, the A725 Corridor and the M73 / M74 Corridor. Journey time impacts on each of these sections are described in the following report sections.

M8 Corridor

The average post-opening journey times, along with the savings in travel time within the M8 Corridor, between Baillieston and Newhouse, are shown in Figure 36.

The analysis of journey times within the M8 Corridor, presented in Figure 36, indicates that average post-opening journey times are:

• Likely to have reduced compared to pre-opening journey times, in the eastbound and westbound directions of travel, in the AM survey period, in the order of 2 ½ minutes.
• Broadly consistent with pre-opening journey times, in the eastbound and westbound directions of travel, in the IP survey period.
• Likely to have reduced compared to pre-opening journey times, in the eastbound and westbound directions of travel, in the PM survey period, in the order of 2 minutes.

Based on the analysis outlined above, it can be judged that the provision of a motorway standard route between Baillieston and Newhouse has resulted in a significant positive impact on strategic east / west journey times within the M8 Corridor. The impact of congestion inherent on the previous A8 has been mitigated, with average savings in journey times of around 2 to 2 ½ minutes realised for road users during the AM and PM survey periods.

Cognisance of the basis of this analysis should be taken when interpreting the impacts resulting from the project. Savings in journey times, as described in this section of the report, are based on average savings in each survey period – it is reasonable to expect that savings of a greater magnitude could be realised within the M8 Corridor. The magnitude of the potential savings in journey times is discussed later in this report.

A725 Corridor

The average post-opening journey times, along with the savings in travel time within the A725 Corridor, are shown in Figure 37.

The analysis of journey times within the A725 Corridor, presented in Figure 37, indicates that average post-opening journey times are:

• Likely to have reduced compared to pre-opening journey times, in the northbound and southbound directions of travel, in the AM survey period, in the order of between 5 ½ and 7 ½ minutes.
• Likely to have reduced compared to pre-opening journey times, in the northbound and southbound directions of travel, in the IP survey period, in the order of between 1 and 1 ½ minutes.
• Likely to have reduced compared to pre-opening journey times, in the northbound and southbound directions of travel, in the PM survey period, in the order of between 6 and 6 ½ minutes.

Based on the analysis outlined above, it can be judged that the provision of a fully grade separated junction at Raith (with an underpass provided for A725 traffic), and improvements to A725 / M8 connections at M8 Junction 7a Shawhead, has resulted in a significant positive impact on strategic journey times for north / south traffic within the A725 Corridor. The impact of queuing and congestion inherent at the former Raith Junction have been successfully mitigated, with average savings in journey times of up to 7 ½ minutes realised for road users during the AM survey period.

Cognisance of the basis of this analysis should be taken when interpreting the impacts resulting from the project. Savings in journey times, as described in this section of the report, are based on average savings in each survey period – it is reasonable to expect that savings of a greater magnitude could be realised within the A725 Corridor. The magnitude of the potential savings in journey times is discussed later in this report.

M73 / M74 Corridor

The average post-opening journey times, along with the savings in travel time within the M73 / M74 Corridor, are shown in Figure 38.

The analysis of journey times within the M73 / M74 Corridor, presented in Figure 38, indicates that average post-opening journey times are:

• Likely to have reduced compared to pre-opening journey times, in the southbound direction of travel, in the AM survey period, in the order of ½ minute.
• Broadly consistent with pre-opening journey times, in the northbound and southbound directions of travel, in the IP survey period.
• Broadly consistent with pre-opening journey times, in the northbound and southbound directions of travel, in the PM survey period.

The available travel time data suggests that average journey times within the M73 / M74 Corridor have not changed significantly following opening of the project. While the additional capacity provided on the M73 and M74 has undoubtedly resulted in improvements in the flow of traffic during peak periods, particularly on the M74 approach to Junction 4 Maryville and Junction 5 Raith, the implementation of a 50 mph speed limit as part of the project on the section of the M73 between Junction 1 Maryville and Junction 2 Baillieston (to reduce the effects of merging / weaving traffic on this section of the network) may have the potential to negate savings in journey times on other sections of the route.

Cognisance of the basis of this analysis should be taken when interpreting the impacts resulting from the project. Savings in journey times, as described in this section of the report, are based on average savings in each survey period – it is reasonable to expect that savings of a greater magnitude could be realised within the M73 / M74 Corridor. The magnitude of the potential savings in journey times is discussed later in this report.

M8 / M74 Movements

The average post-opening journey times, along with the savings in travel time between the M8 at Baillieston and the M74 at Carmyle, are shown in Figure 39.

The analysis of journey times for trips travelling between the M8 and M74, presented in Figure 39, indicates that average post-opening journey times are:

• Likely to have reduced compared to pre-opening journey times, in the eastbound direction of travel, in the AM survey period, in the order of 3 ½ minutes.
• Likely to have reduced compared to pre-opening journey times, in the eastbound and westbound directions of travel, in the IP survey period, by up to 1 minute.
• Likely to have reduced compared to pre-opening journey times, in the eastbound and westbound directions of travel, in the PM survey period, in the order of between ½ minute and 3 minutes.

The available travel time data suggests that average journey time savings are more pronounced in the eastbound than westbound direction of travel. This is primarily due to the queuing that formed as a result of traffic accessing the M73 (towards Baillieston) from the eastbound M74 . Anecdotal evidence points to the previous layout of the M73 / M74 merge as having contributed to queuing at this location, which could frequently extend back along the M74 towards Carmyle, particularly during peak periods.

In the westbound direction of travel, in the AM survey period, the available travel time data suggests that post-opening journey times may increase, compared to pre-opening conditions, in the order of ½ minute. This is due to the combined impact of the implementation of a 50 mph speed limit as part of the project on the section of the M73 between Junction 1 Maryville and Junction 2 Baillieston (to reduce the effects of merging / weaving traffic on this section of the network) and queuing on the westbound M74. Anecdotal evidence indicates slow moving traffic on the westbound M74 can frequently extend from M8 Junction 22 (the merge of the M74 / M8 south of the Kingston Bridge) particularly during the AM period.

Cognisance of the basis of this analysis should be taken when interpreting the impacts resulting from the project. Savings in journey times, as described in this section of the report, are based on average savings in each survey period – it is reasonable to expect that savings of a greater magnitude could be realised for trips travelling between the M8 and M74.

Comparison Between Pre and Post-Opening Travel Time Variability

Further analysis of the available journey time information indicates that pre-opening peak period journey times could be considerably greater than the average due to the impact of the volume of traffic using the network during these periods. The distribution of journey times on key sections of the upgraded network are described in the following report sections.

M8 Corridor

The distribution of journey times within the M8 Corridor, between Baillieston and Newhouse, in the eastbound and westbound directions of travel respectively, are shown in Figure 40 and Figure 41.

As can be seen from Figure 40 and Figure 41, pre-opening journey times were significantly greater during the AM and PM survey periods, in the eastbound and westbound directions of travel respectively. The impact of significant delays and congestion have now been largely removed, as indicated by the shorter journey times observed post-opening. Maximum journey time durations have, therefore, been reduced significantly and the variability of journey times on this section on the M8 lessened.

Based on post-opening free flow journey times of around 6 minutes, it can be deduced that, based on a comparison of the available pre and post-opening journey times, maximum savings in the order of 9 to 10 minutes could be realised following opening of the project for journeys undertaken during peak periods within the M8 Corridor.

Cognisant of the fact that, while the pre and post-opening journey time data sets used to inform the evaluation provide a suitable basis on which to evaluate the likely impacts of the project, it should be recognised that maximum journey time savings, over and above those identified from the comparison of the available data at the time of the 1YA Evaluation, could be realised. It is known that delays and, subsequently, journey durations greater than those captured as part of the pre-opening data set were observed prior to project opening. As such, maximum journey time savings greater than the 9 to 10 minutes observed from the available data, could have been realised during peak periods. The magnitude of these journey time savings, however, cannot be quantified.

A725 Corridor

The distribution of journey times within the A725 Corridor, in the northbound and southbound directions of travel respectively, are shown in Figure 42 and Figure 43.

As can be seen from Figure 42 and Figure 43, pre-opening journey times were significantly greater during the AM and PM survey periods, in the northbound and southbound directions of travel respectively. The impacts of the significant queuing and congestion inherent at Raith Junction have now been removed, as indicated by the shorter journey times observed post-opening. Maximum journey time durations have, therefore, been reduced significantly and the variability of journey times within the A725 Corridor lessened.

Based on post-opening free flow journey times of around 6 to 7 minutes, it can be deduced that, based on a comparison of the available pre and post-opening journey times, maximum savings in the order of 30 minutes could be realised following opening of the project for journeys undertaken during peak periods within the A725 Corridor.

M73 / M74 Corridor

The distribution of journey times within the M73 / M74 Corridor, in the northbound and southbound directions of travel respectively, are shown in Figure 44 and Figure 45.

As can be seen from Figure 44 and Figure 45, pre-opening journey times were significantly greater during the AM and PM survey periods, in the northbound and southbound directions of travel respectively. The additional capacity provided on the M73 and M74 is having a positive impact on journey times, as indicated by the shorter journey durations observed post-opening. Maximum journey time durations have, therefore, been reduced significantly and the variability of journey times within the M73 / M74 Corridor lessened.

Based on post-opening free flow journey times of around 8 to 9 minutes, it can be deduced that, based on a comparison of the available pre and post-opening journey times, maximum savings in the order of 11 minutes could be realised following opening of the project for journeys undertaken during peak periods within the M73 / M74 Corridor.

Summary of Journey Time Variability Impacts

Pre and post-opening journey times, presented within time bands, are outlined in the following section to better define the impact on the variability of journey times resulting from the project.

Comparison of Pre & Post-Opening Journey Time Variability – M8 Corridor

Pre and post-opening journey time bands within the M8 Corridor, in the eastbound and westbound directions of travel respectively, are presented in Figure 46 and Figure 47 and are detailed below.

Comparison of Pre & Post-Opening Journey Time Variability – M8 Corridor, Eastbound

• Less than 6 minutes
  • Pre-Opening: 23%
  • Post-Opening: 70%
  6 – 8 minutes

Comparison of Pre & Post-Opening Journey Time Variability – M8 Corridor, Westbound

• Less than 6 minutes
  • Pre-Opening: 29%
  • Post-Opening: 58%
  6 – 8 minutes

Summary of Pre & Post-Opening Journey Time Variability – M8 Corridor

As can be seen from the information presented in Figure 46 and Figure 47, the proportion of journey times of longer durations has reduced significantly as a result of the project. Based on the information presented, it can be judged that:

• The proportion of journey times of six minutes or less has increased from approximately 23% and 29% pre-opening to approximately 70% and 58% post-opening, in the eastbound and westbound directions of travel respectively.
• The proportion of journey times of ten minutes or greater has significantly decreased from approximately 23% and 16% pre-opening to approximately 2% and 0% post-opening, in the eastbound and westbound directions of travel respectively.

The analysis of journey times presented in Figure 46 and Figure 47 adds weight to the conclusion that, not only has the project resulted in average journey time savings but, additionally, has resulted in reductions in the proportion of longer journey times. It can be judged, therefore, that the project has delivered a reduction in the variability of journey times within the M8 Corridor.

Comparison of Pre & Post-Opening Journey Time Variability – A725 Corridor

Pre and post-opening journey time bands within the A725 Corridor, in the northbound and southbound directions of travel respectively, are presented in Figure 48 and Figure 49 and are detailed below.

Comparison of Pre & Post-Opening Journey Time Variability – A725 Corridor, Northbound

• Less than 8 minutes
  • Pre-Opening: 18%
  • Post-Opening: 75%
  8 – 10 minutes

Comparison of Pre & Post-Opening Journey Time Variability – A725 Corridor, Southbound

• Less than 8 minutes
  • Pre-Opening: 11%
  • Post-Opening: 82%
  8 – 10 minutes

Summary of Pre & Post-Opening Journey Time Variability – A725 Corridor

As can be seen from the information presented in Figure 48 and Figure 49, the proportion of journey times of longer durations has reduced significantly as a result of the project. Based on the information presented, it can be judged that:

• The proportion of journey times of eight minutes or less has increased significantly from approximately 18% and 11% pre-opening to approximately 75% and 82% post-opening, in the northbound and southbound directions of travel respectively.
• The proportion of journey times of ten minutes or greater has significantly decreased from approximately 42% and 44% pre-opening to approximately 10% and 2% post-opening, in the northbound and southbound directions of travel respectively.

The analysis of journey times presented in Figure 48 and Figure 49 adds weight to the conclusion that, not only has the project resulted in average journey time savings but, additionally, has resulted in reductions in the proportion of longer journey times. It can be judged, therefore, that the project has delivered a reduction in the variability of journey times within the A725 Corridor.

Comparison of Pre & Post-Opening Journey Time Variability – M73 / M74 Corridor

Pre and post-opening journey time bands within the M73 / M74 Corridor, in the northbound and southbound directions of travel respectively, are presented in Figure 50 and Figure 51 and are detailed below.

Comparison of Pre & Post-Opening Journey Time Variability – M73 / M74 Corridor, Northbound

• Less than 8 minutes
  • Pre-Opening: 5%
  • Post-Opening: 0%
  8 – 10 minutes

Comparison of Pre & Post-Opening Journey Time Variability – M73 / M74 Corridor, Southbound

• Less than 8 minutes
  • Pre-Opening: 21%
  • Post-Opening: 0%
  8 – 10 minutes

Summary of Pre & Post-Opening Journey Time Variability – M73 / M74 Corridor

As can be seen from the information presented in Figure 50 and Figure 51, the proportion of journey times of longer durations has reduced as a result of the project. Based on the information presented, it can be judged that:

• The proportion of journey times of ten minutes or less has increased from approximately 95% and 89% pre-opening to approximately 100% post-opening, in the northbound and southbound directions of travel respectively.
• The proportion of journey times of ten minutes or greater has decreased from approximately 5% and 11% pre-opening to approximately 0% post-opening, in the northbound and southbound directions of travel respectively.

The analysis of journey times presented in Figure 50 and Figure 51 confirms that, while average journey time savings within the M73 / M74 Corridor are not judged to be significant, the project has resulted in reductions in the proportion of longer journey times. It can be judged, therefore, that the project has delivered a reduction in the variability of journey times within the M73 / M74 Corridor.

Comparison Between Predicted and Actual Travel Times

In order to understand the accuracy of the predictions made as part of the project’s assessment, a comparison of predicted and actual average journey time savings has been undertaken.

Predicted average journey time savings have been derived from the traffic models used to inform the project’s assessment. The traffic models provide journey time savings in each of the model forecast years (2017, 2022 and 2022). Predicted average journey time savings derived from the 2017 reference and scheme models have been used to inform the evaluation. This is on the basis that the predicted average journey time savings in 2017 are likely to provide the most representative comparison with actual average journey time savings observed in 2019

The comparison of predicted and actual average journey time savings, for the M8 Corridor, between Baillieston and Newhouse, the A725 Corridor and the M73 / M74 Corridor is shown in Figure 52, Figure 53 and Figure 54 respectively.

Based on the comparison of predicted and actual journey time savings presented in Figure 52, Figure 53 and Figure 54, it can be deduced that:

• Actual average journey time savings are, generally, somewhat greater (in the order of ½ minute to 2 ½ minutes), compared to predicted journey time savings, in both directions of travel, across all time periods, within the M8 Corridor. This is with the exception of the westbound direction of travel, in the PM period, where predicted average journey time savings are in the order of 1 ½ minutes greater than observed.
• Actual average journey time savings are, somewhat greater (in the order of ½ minute to 5 minutes), compared to predicted journey time savings, in both directions of travel, across all time periods, within the A725 Corridor.
• Actual average journey time savings are, generally, somewhat lower (in the order of ½ minute to 1 minute), compared to predicted journey time savings, in both directions of travel, across all time periods, within the M73 / M74 Corridor. This is with the exception of the southbound direction of travel, in the AM period, where actual average journey time savings are in the order of 1 minute greater than predicted.

On this basis, it can be judged that, overall, the predicted average journey time savings derived from the traffic models developed to support the project’s assessment do not vary considerably from observed average journey time savings. It is worth noting, however, that actual average journey time savings tend to be greater when compared to predictions (most notably within the A725 Corridor). As such, the project may be delivering average savings in journey time over and above those predicted as part of the project’s assessment.

Travel Times: Key Findings

The project has resulted in significant reductions in journey times across the upgraded road network. Average journey time savings of up to 2 ½ minutes within the M8 Corridor, up to 7 ½ minutes in the A725 Corridor and up to 3 ½ minutes for traffic travelling between the M74 and M8, via the M73, have been observed following opening. Savings within the M73 / M74 Corridor have also been observed, albeit of a lower magnitude.

Based on the information available at the time of the 1YA Evaluation, it can be deduced that, during peak periods, the project could deliver greater journey time savings, in the order of 9 to 10 minutes within the M8 Corridor, in the order of 30 minutes within the A725 Corridor and around 11 minutes within the M73 / M74 Corridor.

While the pre and post-opening journey time data sets used to inform the evaluation provide a suitable basis on which to evaluate the likely impacts of the project, it is known that delays and, subsequently, journey durations greater than those captured as part of the pre-opening data set were observed prior to project opening. As such, maximum journey time savings greater than those observed from the available data, could have been realised during peak periods. The magnitude of these journey time savings, however, cannot be quantified.

The project has also been found to have resulted in significant reductions in the variability of journey times across the upgraded road network. The proportion of journey times of longer durations has reduced significantly following opening of the project, with notable decreases in the proportion of journey times of 10 minutes or greater within both the M8 and A725 Corridors. Reductions in the variability of journey times have also been observed within the M73 / M74 Corridor, albeit of a lower magnitude.

Overall, predicted average journey time savings derived from the traffic models developed to support the project’s assessment do not vary considerably from observed average journey time savings. Actual average journey time savings, however, tend to be greater when compared to predictions (most notably within the A725 Corridor). As such, the project may be delivering average savings in journey time over and above those predicted as part of the project’s assessment.

Vehicle Speeds

Comparison Between Pre and Post-Opening Vehicle Speeds

Pre and post-opening average vehicle speeds have been compared in order to understand the impact of the project across the upgraded network. Average vehicle speeds have been derived from the pre and post-opening journey time information collected in April & May 2014 and October & November 2019 respectively.

To capture the varying conditions across the day, average vehicle speeds have been calculated based on the journey time data collected during the following survey periods:

• AM Survey Period – 07:00 – 10:00
• IP Survey Period – 11:00 – 14:00
• PM Survey Period – 16:00 – 19:00

The change in post-opening vehicle speeds, within the AM, IP and PM survey periods, is presented in Figure 55, Figure 56 and Figure 57 respectively.

As can be seen from the data presented in Figure 55, Figure 56 and Figure 57, the project has largely resulted in increases in average vehicle speeds (substantially in certain locations) across the upgraded network.

In the AM period, significant changes in average vehicle speeds are noted at certain locations across the upgraded network. Within the M8 Corridor, between Baillieston and Newhouse, average vehicle speeds, in the eastbound direction of travel, have increased by up to 30 mph following project opening. In the westbound direction of travel, average vehicle speeds between Newhouse and Shawhead have increased by up to 40 mph, largely as a result of the alleviation of the congestion previously inherent on the network at this location. Between Shawhead and Baillieston, average vehicle speeds are marginally lower on approach to the Baillieston Interchange. This is partially due to the increased volume of traffic travelling between the M8 and M74 northbound (via the M73), as an alternative to travelling the M8, via the Kingston Bridge.

Within the A725 Corridor, average vehicle speeds, on both the northbound and southbound approaches to the Raith Junction have increased significantly following grade separation and the alleviation of the significant queuing previously experienced at this location. Changes in average vehicle speeds of up to 40 mph are noted. Elsewhere within the corridor, changes in average speeds are noted, albeit of a lower magnitude.

Changes in average vehicle speeds within the M73 / M74 Corridor are most pronounced on approach to the key junctions. Increases in average speeds of up to 30 mph are noted on the M73 southbound approach to Baillieston with increases of up to 20 mph noted on the M74 southbound approach to Junction 4, Maryville and Junction 5, Raith. Changes in average speeds of a lower magnitude i.e. up to 10 mph are noted on the M74 in the northbound direction of travel between Junction 6, Hamilton and Junction 4, Maryville and on the M73, in the northbound direction of travel to the north of Baillieston Interchange. Marginal reductions in average speeds are noted south of Junction 2 Baillieston, in part due to the reduction in the speed limit of the route to 50 mph. Larger reductions in average speeds are noted on the M74 northbound on approach to Junction 3, Carmyle. This is largely due to queuing on the westbound M74, which anecdotal evidence indicates can frequently extend from M8 Junction 22 (the merge of the M74 / M8 south of the Kingston Bridge) particularly during the AM period.

In the IP period, changes in average vehicle speeds are more muted. This, however, is as expected given the largely free flow nature of traffic during this period prior to the upgrading of the network. Increases in average vehicle speeds of between zero and 10 mph are noted within the M8 Corridor between Baillieston and Newhouse.

Within the A725 Corridor, changes in average vehicle speeds on the northbound A725 approach to the Raith Junction of up to around 30 mph have been derived using the available journey time data.

Elsewhere within the A725 Corridor, changes in average vehicle speeds are relatively insignificant i.e. within the range plus or minus up to 10 mph. It is a similar picture within the M73 / M74 Corridor, with minimal changes in average vehicle speeds. On the M74 between Junction 6, Hamilton and Junction 3 Carmyle, increases in average vehicle speeds of up to 10 mph are noted. On the M73, to the north of Baillieston, increases in average vehicle speeds of up to 10 mph are noted. Between Junction 1, Maryville and Junction 2, Baillieston, reductions in average vehicle speeds of up to 20 mph are noted. This is as a result of the reduction in speed limit, from the motorway national speed limit, to 50 mph. This has been implemented as part of the improvements to facilitate safer merging and weaving of traffic on this section of the network.

In the PM period, significant changes in average vehicle speeds are noted at certain locations across the upgraded network. Within the M8 Corridor, between Baillieston and Newhouse, average vehicle speeds, in the eastbound direction of travel, have increased by up to 30 mph following project opening. In the westbound direction of travel, average vehicle speeds between Newhouse and Shawhead have increased by up to 40 mph, largely as a result of the alleviation of the congestion previously inherent on the network at this location. Between Shawhead and Baillieston, average vehicle speeds are marginally lower on approach to the Baillieston Interchange. This is partially due to the increased volume of traffic travelling between the M8 and M74 northbound (via the M73), as an alternative to travelling the M8, via the Kingston Bridge.

Within the A725 Corridor, average vehicle speeds, on both the northbound and southbound approaches to the Raith Junction have increased significantly following grade separation and the alleviation of the significant queuing previously experienced at this location. Changes in average vehicle speeds of up to 40 mph are noted. Elsewhere within the corridor, changes in average speeds are noted, albeit of a lower magnitude with reductions in average speeds noted in the northbound direction of travel on approach to the interchange with the M8.

Changes in average vehicle speeds within the M73 / M74 Corridor are most pronounced on approach to the key junctions. Increases in average speeds of up to 20 mph are noted on the M73 southbound approach to Junction 2, Baillieston and on the M74 southbound approach to Junction 4, Maryville.

Changes in average speeds of a lower magnitude i.e. up to 10 mph are noted on the M74 in the northbound direction of travel between Junction 6, Hamilton and Junction 4, Maryville and on the M73, in the northbound direction of travel to the north of Baillieston Interchange. Marginal reductions in average speeds are noted on the M74 south of Junction 4, Maryville and on the M73 south of Junction 2, Baillieston, which is in part due to the reduction in the speed limit of the route to 50 mph.

It has been observed, albeit anecdotally, that sections of the network directly adjacent to, but outwith, the evaluation study area are subject to queuing and congestion (and subsequently, lower vehicle speeds) during certain periods of the day – primarily during the AM and / or PM peak periods. One such section is the A725, on approach to the Whirlies Roundabout, in East Kilbride. Queuing and congestion on approach to the junction (which can extend over a couple of kilometres) regularly occurs during the AM and PM periods. It is judged that this is likely due, in part, to the volume of traffic using this route but, also, potentially due to the removal of the pre-opening bottleneck on the network at the Raith Junction. The largely free flow conditions on the A725 at the Raith Junction facilitates the smoother flow of local and strategic traffic on this part of the road network. It is likely that traffic previously constrained by the delays and congestion that were inherent on the A725 approaches to Raith Junction are now able to more quickly complete journeys along this section of the A725, joining and increasing the length of the queue on approach to the Whirlies Roundabout.

One further section is the M74 northbound. Queuing and congestion can extend from Junction 5 Raith to, in the most severe cases, Junction 8 Canderside (south of Larkhall) – a section of some 12 kilometres - during the AM period. It is judged that this is likely due, in part, to the volume of traffic using this route but, also, potentially due to the removal of the bottleneck on the network at the Raith Junction. The largely free flow conditions on the A725 at Raith facilitates the smoother flow of traffic through the junction. It is likely that traffic constrained by the delays and congestion that were previously inherent on this section of the network are now able to more quickly complete journeys along the A725, joining the M74 at Raith. It is considered, albeit anecdotally, that the volume of traffic merging with northbound M74 traffic, in the most severe cases, can result in significant queuing and congestion on the northbound M74, from the northbound merge at Junction 5 Raith.

It is outwith the scope of the 1YA Evaluation to assess and quantify actual and / or perceived operational issues on sections of the network outwith the 1YA Evaluation study area.

Transport Scotland will continue to liaise with its local authority and operating company partners to identify, assess and mitigate operational constraints on the trunk road network, through targeted interventions, major infrastructure projects or influencing shifts in travel behaviour.

Vehicle Speeds: Key Findings

Based on the information available at the time of the 1YA Evaluation, it is judged that the project has, generally, had a significant positive impact reducing delays and consequently increasing vehicle speeds across the upgraded road network. Significant increases in average vehicle speeds in the AM and PM periods, within the M8 Corridor, have been observed following opening of the project largely as a result of the alleviation of the congestion previously inherent on the network at this location. Similarly, significant increases in average vehicle speeds have been observed during peak periods on both the northbound and southbound approaches to the Raith Junction. This is as a direct result of the grade separation of the junction and the alleviation of the significant queuing previously experienced at this location. Increases in average vehicle speeds within the M73 / M74 Corridor are most pronounced on approach to the key junctions i.e. Baillieston and Maryville.

In the IP period, while changes in average vehicle speeds across the upgraded road network are more muted, this is as expected given the largely free flow nature of traffic during this period prior to the upgrading of the network.

Anecdotal evidence suggests that sections of the network directly adjacent to, but outwith, the evaluation study area are subject to queuing and congestion (and subsequently, lower vehicle speeds) during certain periods of the day – primarily during the AM and / or PM peak periods. It is outwith the scope of the 1YA Evaluation to assess and quantify actual and / or perceived operational issues on sections of the network outwith the 1YA Evaluation study area.

Transport Scotland will continue to liaise with its local authority and operating company partners to identify, assess and mitigate operational constraints on the trunk road network, through targeted interventions, major infrastructure projects or influencing shifts in travel behaviour.

Intelligent Transport System (ITS) Impacts

As part of the project’s development, the CSTCS report recommended the use of “electronic variable speed limit signs mounted on gantries to control traffic speeds on the new section of motorway”.

The project was delivered with ITS provision across the upgraded road network, in-line with Transport Scotland’s ITS Strategy, including gantry mounted variable speed limit signs and Variable Message Signs (VMS). The former are used during times of higher traffic volumes (primarily during peak periods) providing a warning to road users to reduce their speed on approach to congestion on the road network, or in the event of an incident (such as a breakdown or road traffic accident).

In the case of the M8 M73 M74 Motorway Improvements Project, variable speed limits are advisory only – mandatory variable speed limits are not enforced across the upgraded road network. In terms of the project VMS, these provide road users with travel information, typically including warnings of current and / or planned road works, road closures, weather events and other events which could lead to delays or congestion, on the wider strategic road network.

An example of the ITS measures provided as part of the project, including overhead gantries and VMS, is presented in Figure 58 and Figure 59.

Post-Opening Impact of ITS Measures

At the time of the 1YA Evaluation, due to the limited availability of relevant information, the impact of the ITS measures provided as part of the project cannot be quantified. It can be judged, however, that the use of ITS, including variable speed limits during times of congestion and when incidents occur, and VMS information informing road users of wider issues or events on the strategic road network, contribute to optimising the benefits of the project. This is as a direct result of the ITS measures provided facilitating the efficient use of the strategic road network, both within the project extents and more widely across the adjacent trunk road network.

The impact of the ITS measures provided as part of the project will be evaluated and quantified as part of a subsequent 3YA and / or 5YA evaluation for the project, once sufficient and relevant information is available.

Intelligent Transport System (ITS): Key Findings

The project was delivered with ITS provision across the upgraded road network, including gantry mounted variable speed limit signs and VMS. At the time of the 1YA Evaluation, the impact of the ITS measures provided cannot be quantified. It can be judged, however, that the use of ITS is contributing to the optimisation of the project benefits, through enabling the efficient use of the road infrastructure provided, both within the project extents and more widely across the adjacent trunk road network.

The impact of the ITS measures provided as part of the project will be evaluated and quantified as part of a subsequent 3YA and / or 5YA evaluation for the project, once sufficient and relevant information is available.

Local Network Impacts

While the road network upgraded as part of the project primarily focussed on the trunk road network, alterations to the local road network have been made at the project ‘tie in’ points at several locations. These alterations were primarily located within the boundaries of North Lanarkshire and South Lanarkshire local authority areas. As such, NLC and SLC were both offered the opportunity, as part of the 1YA Evaluation, to provide any relevant data relating to traffic conditions that was deemed, in the views of the local authorities, of importance to the evaluation. SLC provided long-term traffic count data from a permanent ATC located on the B7071 Bothwell Road, around 400 metres south of Bothwell Bridge. No suitable and / or relevant data was provided by NLC.

Post-Opening Queuing Conditions

Whilst suitable pre-opening data is not available for comparative purposes, post-opening data was collected, in November 2019, to provide an understanding of operating conditions at specific local road network locations. Maximum queue length data, was collected on multiple weekdays, over a 12-hour survey period (07:00 – 19:00), at the following seven locations (maximum queue lengths recorded as number of vehicles in a queued state):

• Q1 – A7071 / B7071 Bothwell Road Signalised Junction
• Q2 – A7071 / A725 northbound off-slip Signalised Junction
• Q3 – Raith Junction
• Q4 – A725 / North Road / A8 Westbound on/off-slips Signalised Junction
• Q5 – A725 / A8 Eastbound on/off-slips Signalised Junction
• Q6 – A725 Shawhead North Signalised Junction
• Q7 – Baillieston Roundabout

The queue survey locations, as described above, are presented in Figure 60.

A7071 / B7071 Bothwell Road Junction

Prior to opening of the project, the A7071 / B7071 Bothwell Road Junction took the form of a 3-arm non-signalised mini roundabout. As part of the project, the layout was altered to create a 3-arm signalised priority junction.

Post-opening queuing data collected at the A7071 / B7071 Bothwell Road junction indicates significant queuing on certain approaches to the junction, particularly during the AM and PM peak periods. In particular, queuing on the B7071 Bothwell Road, northbound approach to the junction, can cause significant delays for traffic. The maximum queues on the northbound approach to the junction, in 30-minute intervals, are presented in Figure 61.

As can be seen from the information presented in Figure 61, maximum queues of up to 150 vehicles during the PM period were observed within the November 2019 survey period. Maximum queues of between 120 and 130 vehicles were observed in the AM period (between 08:00 and 09:30) with maximum queues of between 100 and 150 vehicles observed during the PM period, between 15:30 and 18:00. Observed maximum queue levels over the remainder of the survey period were of a lower magnitude, typically around 20 to 30 vehicles.

An example of queuing conditions on the northbound B7071 approach to the junction, in the PM period, looking towards and away from the junction, is presented in Figure 62 and Figure 63 respectively.

Long-term traffic count data, supplied by SLC, to support the 1YA Evaluation, indicates that post-opening traffic volumes on the B7071 Bothwell Road, south of the junction, are somewhat lower when compared with pre-opening levels. Figure 64 presents a summary of the change in average daily traffic profiles pre and post-opening of the project on the B7071 Bothwell Road.

As can be seen from the information presented in Figure 64, average daily 2-way traffic volumes are up to 400 vehicles per hour, lower following opening of the project, i.e. between 07:00 and 08:00, with an overall reduction in the volume of traffic using the route of over 2,000 vpd. In the northbound direction of travel (on approach to the junction), hourly traffic volumes during the morning peak (between 07:00 and 08:00) are up to approximately 330 vehicles lower following opening of the project, with an overall reduction in traffic of around 1,700 vpd. Given the magnitude of the reductions observed on approach to the junction, particularly during peak periods, it is reasonable to assume that road users may be choosing to take alternative routes (such as accessing the M74 at Junction 6 Hamilton) to avoid queuing and congestion on approach to the junction.

Cognisance of the impact of wider changes within the local area should be taken when interpreting general changes in traffic volumes at this location. These include the relocation of the University of the West of Scotland (UWS) Hamilton Campus, from Almada Street to the Hamilton International Technology Park, in Autumn 2018.

Based on the observed data collected in November 2019, it can be deduced that maximum queues are of a level that are likely to be negatively perceived by road users travelling on the B7071. The level of queuing observed may contribute to poor perceptions of journey time reliability for local trips to Bothwell, Uddingston and beyond, in addition to similar concerns for those accessing the trunk road network at the Raith Junction. Furthermore, the proximity of the Scottish Fire and Rescue West Delivery Area Headquarters to the junction is such that rapid access for emergency service vehicles could be hindered during peak periods, as a result of the level of queuing at this location.

Transport Scotland will continue to monitor traffic conditions at the junction, liaising with local authority partners to ensure the flow of traffic is optimised. A further 3YA and / or 5YA evaluation will be undertaken for the project, which will include a review of traffic conditions.

A7071 / A725 Northbound Off-slip Junction

The A7071 / A725 Northbound Off-slip Junction facilitates access to and from the trunk road network for road users travelling to Hamilton, Bothwell and Uddingston, in addition to road users travelling northbound on the A725 from the direction of East Kilbride. The A725 northbound off-slip approach provides a link for strategic northbound A725 traffic to the M74 at the Raith Junction.

Queuing data collected at the A7071 / A725 Northbound off-slip junction indicates significant queuing on certain approaches to the junction, particularly during the AM peak period. In particular, queuing on the northbound off-slip from the A725 East Kilbride Expressway approach to the junction, can cause significant delays for traffic. The maximum queues on the A725 northbound off-slip approach to the junction, in 30-minute intervals, are presented in Figure 65.

As can be seen from the information presented in Figure 65, maximum queues of up to 100 vehicles during the AM period were observed within the November 2019 survey period. Maximum queues of up to around 90 vehicles were observed during the PM period (between 17:00 and 17:30) however, maximum queue levels appear more pronounced within the AM period, with maximum queues of between 60 and 100 vehicles observed over the period 07:00 to 09:30. Observed maximum queue levels over the remainder of the survey period were of a lower magnitude, typically around 20 to 30 vehicles.

An example of queuing conditions on the A725 Northbound off-slip approach to the junction, in the PM period, with queuing traffic extending back onto the northbound A725 East Kilbride Expressway (in this instance, over a distance of approximately 500 metres) is presented in Figure 66.

Based on the observed data collected in November 2019, it can be deduced that maximum queues, particularly during the AM period, are of a level that are likely to be negatively perceived by road users exiting the A725 at the junction and may contribute to poor perceptions of journey time reliability for local trips to Bothwell, Uddingston, Hamilton and beyond, in addition to similar concerns for those accessing the M74 at the Raith Junction.

Post-opening queuing, however, must be considered within the context of pre-opening conditions. While pre-opening queue data is not available to inform the 1YA Evaluation, anecdotally, it is known that pre-opening queues, on the northbound A725 approach to the Raith Junction, were significant in length. As such, while queuing still occurs on approach to the junction post-opening of the project, it is likely that the reduction in the magnitude and, potentially, frequency, of queuing traffic, may still be perceived as an improvement by road users.

Transport Scotland will continue to monitor traffic conditions at the junction to ensure the flow of traffic is optimised. A further 3YA and / or 5YA evaluation will be undertaken for the project, which will include a review of traffic conditions.

Raith Junction

No significant queueing was observed during the November weekday survey periods, suggesting that the junction is currently operating to a satisfactory level. Maximum queues on the M74 northbound and southbound off-slips to the junction, as presented in Figure 67 and Figure 68 were in the order of 40 vehicles, in both the AM and PM peak periods.

Similarly, queuing on the A725 southbound off-slip approach to the junction, as presented in Figure 69, was also not observed as ‘significant’ with maximum queues on approach to the junction in the order of 40 vehicles.

Whilst the weekday observations, based on data collected in November 2019, suggest there is no significant queuing on the M74 and A725 approaches to the junction, Transport Scotland will continue to monitor traffic conditions at the junction to ensure the flow of traffic is optimised. A further 3YA and / or 5YA evaluation will be undertaken for the project, which will include a review of traffic conditions.

A725 / North Road / A8 Westbound On / Off-slips Junction

Queuing data collected at the A725 / North Road / A8 Westbound On / Off- slips Junction indicates significant queuing on certain approaches to the junction, particularly during the AM peak period. In particular, queuing on the northbound A725 approach to the junction, can cause significant delays for traffic. The maximum queues on the A725 northbound approach to the junction, in 30-minute intervals, are presented in Figure 70.

As can be seen from the information presented in Figure 70, maximum queues of up to 170 vehicles during the AM period (between 09:00 and 09:30) were observed within the November 2019 survey period. Observed maximum queue levels over the remainder of the survey period were of a lower magnitude, typically around 20 to 40 vehicles. Whilst significant observed maximum queues in the AM period were observed, queuing over the remainder of the survey period is not considered ‘significant’ given the volume of traffic passing through the junction. As such, based on the November 2019 weekday survey information, it is judged that the junction is currently operating to a satisfactory level.

A725 / A8 Eastbound On / Off-slips Signalised Junction

No significant queueing was observed on any of the approaches to the junction during the November 2019 weekday survey periods, suggesting that the junction is currently operating to a satisfactory level. This is, in part, due to the junction’s proximity to the A725 / North Road / A8 Westbound On / Off-slips and A725 Shawhead North Junctions, both of which limit the volume of traffic reaching the junction is a single traffic signal phase, in the northbound and southbound directions of travel respectively.

Transport Scotland will continue to monitor traffic conditions at, and within the vicinity of, the junction to ensure the flow of traffic is optimised. A further 3YA and / or 5YA evaluation will be undertaken for the project, which will include a review of traffic conditions.

A725 Shawhead North Junction

Queuing data collected at the A725 Shawhead North junction indicates moderate levels of queuing on certain approaches to the junction, particularly during the AM and PM peak periods. In particular, queuing on the Kirkshaws Road approach to the junction can cause significant delays for traffic. The maximum queues on the Kirkshaws Road approach to the junction, in 30-minute intervals, are presented in Figure 71.

As can be seen from the information presented in Figure 71, during the survey period, maximum queues extended to around 60 vehicles, in the AM and PM periods i.e. between 08:30 - 09:30 and 16:00 - 17:30. The junction is signalised and operated using a Microprocessor Optimised Vehicle Actuation (MOVA) control system, which optimises traffic signal timings to permit the highest volume of traffic through the junction with the minimum delays.

During peak periods, the volume of traffic on the main A725 route is significantly greater than during other periods of the day and, additionally, is greater than traffic volumes on adjoining minor roads, such as Kirkshaws Road. During the November 2019 weekday survey, between 16:00 and 17:00, traffic volumes of around 1,500 vehicles were observed on both the northbound and southbound A725 approaches to the junction, compared to around 400 vehicles on the Kirkshaws Road approach. As such, the MOVA system automatically optimises signal timings to ensure lower overall delays at the junction which, during peak periods, likely results in additional ‘green time’ for A725 traffic.

Transport Scotland and its partners will continue to monitor traffic conditions within the vicinity of the M8 M73 M74 Motorway Improvements Project to ensure the flow of traffic is optimised. A further 3YA and / or 5YA evaluation will be undertaken for the project, which will include a review of traffic conditions.

Baillieston Junction

The Baillieston Junction facilities the movement of traffic travelling between the M74, M73 and M8 motorways – a key east / west movement within the study area. Maximum queues on the northbound M73 approach and westbound M8 approach to the junction have been evaluated and are presented in Figure 72 and Figure 73.

As can be seen from the information presented in Figure 72 and Figure 73, while maximum queue lengths are greatest during the AM and PM peak periods, as expected, the magnitude of the maximum queues (in the order of 50 vehicles) is such that they are not considered ‘significant’ given the volume of traffic passing through the junction. As such, based on the November 2019 weekday survey information, it is judged that the junction is currently operating to a satisfactory level and is unlikely to provide any barriers to east / west travel via the M74, M73 and M8.

Local Network Impacts: Key Findings

It is considered that the project, generally, has improved traffic conditions at its interface with the adjoining local road network. Localised issues, however, have become apparent post-project opening, including queuing traffic on certain sections of the network, such as the northbound B7071 Bothwell Road, where queuing in the AM and PM peak periods may potentially be negatively viewed by road users at this location, in terms of the impact on journey time reliability for both local and strategic journeys.

Transport Scotland will continue to monitor traffic conditions at the junction, liaising with local authority partners to ensure the flow of traffic is optimised.

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