Seatbelt and Mobile Phone Usage Survey Scotland, 2014

2. Methodology

2.1 Site Selection

The surveys were carried out by a series of roadside observations at 30 sites in Scotland, including different road (major and minor[12]) and area (urban and rural[13]) types to provide nationally representative estimates. Sites were chosen in locations across Scotland to reflect different levels of road use and traffic volume, and included a number of sites which have been used in previous DfT seatbelt studies[14].

Observation of mobile phone use took place on roads with moving (free-flowing) and stationary (at traffic light controlled junctions) traffic, although the seatbelt survey was only undertaken at stationary sites. Whilst previous DfT mobile phone surveys were only conducted at moving sites, the inclusion of stationary sites in this study allowed for more detailed observations to be made, and also enabled driver behaviour in different situations to be compared.

A breakdown of the sites by road and area category is outlined in Table 2.1. Further details about the survey sites, including location, are provided in Appendix C.

Table 2.1: Distribution of sites in Scotland by site characteristics
Scotland Stationary sites Moving sites Total
Rural Urban Rural Urban
Major 7 4 4 2 17
Minor 4 5 2 2 13
Total 11 9 6 4 30

2.2 Data Collection

Roadside observations were made of occupants of cars, vans, taxis, lorries and buses/coaches.

At moving sites, the gender of drivers was recorded along with whether they were using a hand-held mobile phone, and if so, whether this was to make a call (at-ear) or some other function (in-hand), for example texting.

At stationary sites, the same information as above was recorded for the mobile phone element with driver age and the presence of passengers also recorded.

Additional information was collected on the seatbelt use, age, gender and seating position of all vehicle occupants, except buses and coaches where only information on driver characteristics were recorded. The seatbelt details included additional age categories for children and whether the appropriate child restraint was being used correctly.

The information recorded is outlined in Table 2.2.

Table 2.2: Information recorded by survey and site type (√ = recorded, X = not recorded)
Seatbelt stationary sites Mobile phone stationary sites Mobile phone moving sites
Vehicle characteristics Type: car, van, taxi, lorry, bus (or minibus or coach) √*
Passengers present X X
Driver characteristics Gender
Age group X
Hand-held mobile phone use X
Purpose of hand-held mobile phone use X
Driver restraint use X X
Passenger characteristics Seating position X X
Gender X X
Age group X X
Restraint use X X

*taxis and private hire vehicles separated

Surveys were conducted during half-hour observation periods in October 2014. Each survey site was visited for a half-day session[15] during the week, with selected sites being revisited on Saturdays to provide a representative estimate of behaviour on weekdays and at weekends.

A breakdown of the session times is provided in Table 2.3.

Table 2.3: Survey session times
Morning Session Afternoon Session
Start End Start End
07:30 08:00 13:30 14:00
08:30 09:00 14:30 15:00
09:30 10:00 15:30 16:00
10:30 11:00 16:30 17:00
11:30 12:00 17:30 18:00

Overall, the survey periods accounted for both the morning and evening peak periods so provide a reliable estimate of mobile phone use and seatbelt compliance throughout the day.

2.3 Weighting and Analysis

During all survey periods, traffic counts of all vehicles passing the site were made. This included vehicles where no in-depth observation details were recorded, either because the observer could not accurately record information (if a vehicle passed too quickly or visibility was poor) or because the vehicle was not part of the sample (for example, a moving vehicle passing a stationary site during a green-light phase).

Following collection, the data were quality assured before being weighted using the recorded traffic count and DfT traffic flow data to provide a nationally representative estimate for Scotland across different road and area types.

Therefore, seatbelt wearing rates were calculated as the (weighted) number of relevant vehicle occupants correctly restrained over the (weighted) number of all relevant occupants observed[16]. In the same way, mobile phone usage rates were calculated as the (weighted) number of drivers using a hand-held mobile phone (at-ear and in-hand combined) over the (weighted) number of all drivers observed.

It is worth noting that some records were excluded from certain elements of the analysis process and this is reflected in the sample sizes detailed. The most notable exclusions were:

  • records where mobile phone or seatbelt use was recorded as unknown;
  • records where gender or age were unknown and these were variables being analysed;
  • records relating to one observation period which took place slightly outwith the general survey schedule when analysing usage rates by time of day.

2.4 Comparability

The results reported for both seatbelt compliance and mobile phone use in Scotland in 2014 are comparable with the DfT analysis of the 2014 England and Great Britain data[17] as the findings were established using the same recording, weighting and analysis procedures.

The methodology employed in the seatbelt survey is the same as previous studies so figures presented in this report are comparable with historical data, for example data related to Scotland in 2009. Specifically, it is worth noting is that the fieldwork for the 2009 seatbelt survey was also conducted in October.

However, as previously discussed, data on mobile phone use in Scotland has been recorded for the first time in the current study. The methodology used differed from that previously used for the mobile phone surveys conducted in England as the latest study did not collect information on hands-free mobile phone use but did include mobile phone use at stationary sites for the first time. That being said, the weightings procedure applied both in the past and in the current analysis should allow broad comparison between the figures for overall hand-held use at moving sites (for example, Scotland 2014 findings can be compared with 2009 data for England). It is worth noting that motorway sites were not used in the current survey unlike previous years.

No breakdowns between different types of mobile phone use (at-ear or in-hand) are available for previous years.

2.5 Limitations

There is a general limitation that the data recorded relied on the judgement of roadside observers (for instance, on gender and age). However, this risk was present in all previous examples of the study, yet reliable findings were still achieved due to the large volume of observations made and the weightings procedure followed during analysis. In addition, observers were given extensive training and the data were quality assured prior to analysis.

It is possible that visibility could have been restricted by poor lighting, tinted windows or glare, particularly at moving sites. This may have led to inaccurate data being recorded or certain details being missed. The survey session times were scheduled to avoid problems of poor lighting as far as possible, and this was only reported as having impacted on the survey on one occasion at a survey site in England.

Roadside observers were wearing high-visibility jackets for the purposes of safety and transparency and this may have influenced the behaviour of some drivers. For example, some may have hidden or ended their mobile phone use having detected the observers. Once again, this risk was present in all previous studies.

The survey methodology did not include recording the use of tablets, mp3 players or satellite navigation systems, however being distracted by using such devices is dangerous and also illegal[18]. It is possible that some use of these devices were included in the observation data, for instance if the observer thought a driver was using a mobile phone when in fact it was a tablet. However, observers were trained to specifically look for hand-held mobile phone use.