Scottish Trunk Road Infrastructure Project Evaluation - Evaluation Report for Trunk Road Projects Opened between April 09 and March 10
3 Evaluation Summary
The projects that opened between April 09 and March 10 consist of three carriageway improvements and a junction improvement. A summary of the evaluations is provided below.
Full details of the evaluations for the projects are provided in Appendix A.
Traffic Volumes
Comparison Between Pre and Post Opening Traffic Flows
The Annual Average Daily Traffic (AADT) flows pre and post project opening on the main route of the carriageway and junction improvement projects are shown in Table 3.1.
* flows based on partial data
The comparison between pre and post opening traffic flows indicates that traffic volumes have remained fairly consistent on the A830(T) between Arisaig and Loch Nan Uamh between 2007 to 2011 and that the remaining two projects have experienced a decrease in traffic flows over the same period. Whilst traffic volumes have remained consistent on the A830(T) and A7(T) projects between 2010 and 2011, the A9(T) project experienced a reduction in flows during 2010 but then an increase to pre-scheme levels in 2011.
Given the nature of these projects, changes in post opening traffic levels are not likely to be as a consequence of the improvements and, in part, are likely to be as a result of reductions in traffic volumes across the wider trunk road network in recent years (the reduction between 2009 and 2010 was around 2%) due to the economic downturn.
Comparison Between Predicted and Actual Traffic Flows
A summary of the actual and predicted traffic data on the main route of the carriageway and junction improvement projects is shown in Table 3.2.
* based on first full year of ATC data available after project opening
^ flow based on partial data (August to December)
The comparison between predicted and actual AADT flows for the carriageway and junction improvement projects indicates that three of the four predictions are within the National Audit Office's threshold of +/-20%, which suggests that the modelling techniques used for appraising these types of projects are generally appropriate.
The exception to this is one of the comparisons undertaken for the A9(T) Bankfoot project, where it can be seen that the predicted flow at Dunkeld is around 25% lower than the actual flow (based on the flow observed in 2010, which itself was low).
Carriageway Standard Assessment
An assessment of the carriageway standard according to TA 46/97 - Economic Assessment and Recommended Flow Ranges for New Rural Road Links, which applied at the time of the projects' design, is shown in Table 3.3 based on the opening (or nearest to opening) year flow.
* based on first full year of ATC data available after project opening
^ flows based on available data (August to December)
In order to satisfy the project's objectives, a higher standard of carriageway has been constructed over a section of the A7(T) at Auchenrivock to provide increased overtaking opportunities and help reduce platooning, reduce journey times and improve journey time reliability.
Overtaking Opportunities
One project in this report has objectives relating to Overtaking - the A7(T) Auchenrivock project.
Post Opening Overtaking Opportunities
The impact of the A7(T) Auchenrivock project has been based on the evaluation of other projects with a comparable standard of carriageway in the same geographic region for which overtaking surveys have been carried out. The provision of the wide single 2-lane carriageway is judged to have a positive impact on the number of overtaking manoeuvres.
Travel Times
Comparison Between Pre and Post Opening Travel Times
Pre and post opening travel time information was available for the A830(T) Arisaig to Loch Nan Uamh project. A comparison of the pre and post opening travel times indicates time savings of around 4 to 5 minutes for vehicles using the improved section of the route.
Change in Travel Times
Journey times on the A7(T) at Auchenrivock are expected to have reduced as a consequence of the improvements to road geometry and the provision of a wide single 2-lane carriageway, providing increased overtaking opportunities.
Whilst journey times for some local trips accessing the A9(T) may have marginally increased as a result of the revised junction layout at Bankfoot, it can be expected that journey times on the A9(T) carriageway itself over the extents of the improvement will have reduced in both directions of travel as a result of removing delays to mainline traffic caused by right turning vehicles.
Comparison Between Predicted and Actual Travel Times
A comparison between predicted and actual travel times has been undertaken for the A830(T) Arisaig to Loch Nan Uamh project and indicates that the predicted journey times on the A830(T) between Arisaig and Loch Nan Uamh are around 1 minute longer than the observed journey times in both directions of travel.
Stakeholder feedback
Dumfries and Galloway Council has commented that overtaking opportunities have increased significantly as a result of the project. The Council also suggests that travel times are likely to have been reduced as a result of the scheme.
3.2 Environment
Review of Environmental Mitigation Measures
The environmental mitigation measures contained in the environmental reports, produced at the time the projects were originally assessed, have been examined and compared against the actual measures put in place.
The review of mitigation measures confirmed that the majority of measures committed within the Environmental Statements were in place and were providing appropriate levels of mitigation.
Whilst some variations from the proposed mitigation measures had been identified, these were not considered to have had a material detrimental impact on the general integration of the project into its surrounding.
Areas that require maintenance were identified as part of the environmental mitigation measures review undertaken for A9(T) Bankfoot project.
Noise and Air Quality
Given the rural nature of the carriageway projects and the nature of the A9(T) Bankfoot improvement, no evaluation of the projects' impact on noise and air quality has been undertaken as no significant impacts were anticipated.
3.3 Safety
Accidents
Comparison between Pre and Post Opening Personal Injury Accident Numbers
A summary of the personal injury accident data for all projects is shown in Table 3.4.
For all projects examined in this report, no personal injury accidents have been recorded in the 1 year after opening compared to the numbers recorded during the 3 years before opening.
Road Safety Audits
Stage 4 Road Safety Audit (RSA) reports are available for all the projects that opened between April 09 and March 10.
Whilst some issues concerning pedestrians and cyclists on the A830(T) between Arisaig and Loch Nan Uamh are still to be resolved, an issue surrounding the speed of vehicles on the new section of A7(T) at Auchenrivock has been noted and there is a skid risk from vehicles overrunning filter drain material and scattering it on the A9(T) carriageway at Bankfoot, the RSA findings generally indicate that the projects are operating safely. The findings are summarised within the evaluations presented in Appendix A.
Transport Economic Efficiency
The comparison between predicted and actual traffic flows and travel times, presented in section 3.1, can be considered a proxy for whether the predicted economic benefits of the projects are likely to be realised.
|
Project |
Benefits |
|---|---|
|
A830(T) Arisaig to Loch Nan Uamh |
|
|
A7(T) Auchenrivock |
|
|
A9(T) Bankfoot |
|
actual lower than predicted (over predicted)
actual higher than predicted (under predicted)
= actual as predicted
Due to external factors that could not have readily been foreseen at the time of the assessments, such as the economic downturn, there is a tendency for predicted flows to be overestimated. Whilst this may have resulted in the over-prediction of economic benefits for the A7(T) Auchenrivock project, the comparison between predicted and actual traffic flows is within acceptable limits.
3.5 Integration
One project in this report has objectives that relate to Integration - the A830(T) Arisaig to Loch Nan Uamh (Transport and Policy Integration).
The A830(T) Arisaig to Loch Nan Uamh project accords with the policies contained within the Highland Structure Plan and the Lochaber Local Plan in respect of their objective of promoting the economic development of the area by improving transport links.
Stakeholder feedback
Anecdotal evidence indicates that the interchange experience has been enhanced for bus passengers as a result of more reliable connections and that the A830(T) Arisaig to Loch Nan Uamh project may have played a role in encouraging the use of the Mallaig to Armadale ferry route.
Whilst Calmac ferry passenger figures do report an increase in 2009 compared to 2008, it cannot be confirmed if this increase is directly attributable to the road improvement.
3.6 Accessibility & Social Inclusion
Two projects in this report have objectives that relate to Accessibility & Social Inclusion - the A830(T) Arisaig to Loch Nan Uamh and the A7(T) Auchenrivock.
A new cycle / pedestrian track has been implemented as part of the A830(T) project and has been observed to be in regular use. Some outstanding issues for active travel users are still to be resolved, as identified during the RSA.
A Cycle Audit was carried out as part of the RSA for the A7(T) Auchenrivock project and recommendations have been provided to address potential issues with the measures provided for cyclists.
Stakeholder feedback
Anecdotal evidence indicates that the reduction in journey times and improvement in journey time reliability on the A830(T) between Arisaig and Loch Nan Uamh has had a positive impact on community access and has improved supply chains and linkages between the areas of Mallaig and Arisaig to Fort William.
Investment Costs
Comparison Between Predicted and Out-turn Costs
The out-turn and predicted costs for the three projects are shown in Table 3.6.
The costs are presented in either mid 1998 prices discounted to 1998 at 3.5% or mid 2002 prices discounted to 2002 at 3.5%, depending on the 'present value year' used in the pre‑tender economic assessment.
Of the three comparisons between predicted and actual costs presented in this report, two have an actual project cost higher than the predicted cost. The under prediction can be explained, at least in part, by agreed variations to the project design and claims during the projects' construction.
3.8 Value for Money
A summary of the value for money for the three projects where an economic assessment was undertaken is shown in Table 3.7 based on the qualitative evaluation of economic benefits and quantitative evaluation of project costs presented in sections 3.4 and 3.7 respectively.
actual lower than predicted (over predicted)
actual higher than predicted (under predicted)
= actual as predicted
Based on the evaluation of economic benefits and project costs, it is likely that the A830(T) Arisaig to Loch Nan Uamh project will deliver value for money over and above that predicted at the time of assessment. Whilst the remaining two evaluations indicate that the value for money is unlikely to be as great as predicted, it is judged that the A7(T) Auchenrivock and A9(T) Bankfoot projects will continue to provide a benefit to road users.
3.9 Achievement of Objectives
Initial Indications
Table 3.8 provides an indication of how the projects that opened between April 09 and March 10 are progressing towards achieving their objectives.
Overall, it can be concluded that the projects that opened between April 09 and March 10 are generally progressing towards achieving their objectives.