Discussion, next steps and conclusion

Summary of Findings

The original research question was ‘What factors contribute to the gap between vulnerable road users’ perception of vehicle speeds in comparison to actual speeds on Scotland’s roads?’

By using the relative speed estimate as the dependent variable for statistical analysis, this project is able to provide the following insights:

  • On average, respondents overestimated traffic speeds by 7.5mph.
  • People with a disability that limits their day-to-day mobility or with pets in the household were more likely to overestimate traffic speeds.
  • When we considered factors individually, there was no significant difference between estimation levels across gender, vehicle ownership, children in household, or age.

Taking all of these variables into consideration at the same time through regression modelling, the following demographic factors appear to have a statistically significant impact on overestimation of traffic speeds:

  • Disabilities affecting mobility
  • Pets and/or children in household
  • Access to a vehicle
  • Longer length of time at current address

The following geographic factors also had a statistically significant impact on overestimation of traffic speed:

  • Lower traffic volumes and lower actual speeds
  • Narrower roads
  • Commercial settings
  • Presence of barriers between pedestrians and traffic

In addition to the exploration of the research question, the following notable findings were recorded through other sections of the survey:

  • Traffic speed and volume issues were noted across the day, but the morning and late afternoon were considered the most difficult times, in line with traditional peak period calculations.
  • Speed, volume, and noise of traffic were the most commonly cited barriers to active travel near the trunk road. In respondents’ wider areas, they also cited lighting and crossing times as barriers to active travel.

Implications of Research

On its own, identification of the factors contributing to overestimation of traffic speed is a primarily academic pursuit – but the implications of these findings have the potential to affect the management of trunk roads in Scotland for the benefit of vulnerable road users. Some of these implications are discussed in brief below.

The findings demonstrate that people with caring responsibilities – pets and children – are more likely to overestimate the speed of road traffic, as are people with mobility impairments. Interventions focused on safe road use among these demographics of road users may increase confidence to move about their local area – however, they may also reinforce the message that roads are dangerous, so more research is needed in this area.

Given the relationship between barriers and overestimation of traffic speed, it is similarly possible that safety measures intended to increase vulnerable road users’ safety increase their perception of road traffic being unsafe. This finding is in line with the evolving approach to pedestrian guard railing in transport planning. 

When traffic volume and actual speed are higher, people are more accurate in their estimates of speed. One interpretation of this finding is that a constant flow of traffic is more predictable, whereas the speed of a single vehicle on an otherwise empty road is more difficult to estimate. Measures that regularise traffic flows or otherwise reduce the disruption of less frequent vehicles could reduce perceptions of excessive speeds. 

Similarly, on narrower roads speed estimates are less accurate, potentially due to decreased congruence of the traffic speed with the road aesthetic. Traffic speeds were also more frequently overestimated in retail areas, where pedestrian footfall is likely to be higher. Taken in combination, these findings suggest that measures to slow traffic and clarify traffic speeds (such as high-visibility speed indicator devices) in commercial areas, particularly those with a traditional ‘High Street’ aesthetic, would potentially play a helpful role in attaining a more realistic estimation of vehicle speeds.

Conclusion and Next Steps

Over the course of a four-year research project, WSP investigated local residents’ perception of vehicle speeds in comparison to actual trunk road speeds. The study methodology comprised a literature review, household survey of 13 settlements bisected by a trunk road, statistical analysis and regression modelling to determine the key factors behind overestimation of traffic speed.

The study identified statistically significant demographic and geographic factors leading to this overestimation: people with caring responsibilities or mobility impairments are particularly likely to overestimate speed, and speed overestimation is more likely in areas with pedestrian guard rails, lower traffic flows, narrower roads, and commercial areas.

Further qualitative and experimental research could be undertaken to develop interventions to improve road safety, both perceived and actual, for vulnerable road users in Scotland. To further understand the impact of potential measures, Transport Scotland could consider conducting field trials of speed indicator devices on trunk road high streets in combination or comparison with other interventions to support residents to more accurately estimate speed.

Further research could also be undertaken in the form of focus groups with people from the following demographic groups:

  • Disabilities affecting mobility
  • Pets and/or children in household
  • Long-term area residents

These focus groups could be used to further understand estimation of traffic speed and the impacts of perceived traffic speed on utilitarian and recreational active travel in Scotland.