PRIME site characteristics and behaviour change
Where have PRIMEs been trialled?
In Phase 1 (2020 to 2022) PRIMEs were installed at 22 trunk road sites in the West Highlands of Scotland.
Full details for each trial site are provided including information about the locations, bend directions, what3words, and Google Streetview links (see: Appendix B).
Sites were defined using the following characteristics:
- speed – taking the 85th% speed for a site, where this was below 50mph it was classed as a ‘slower’ approach and if it was above 50mph it was class as a ‘faster’ approach
- gradient – this was classed as either ‘downhill’, ‘flat’, or ‘uphill’ towards the bend
- approach – this was based on whether the bend for the PRIME installation was preceded by another bend or a straight section of road
These characteristics provide the basis for defining 12 bend types (i.e. speed = ‘slower’ or ‘faster’ x gradient = ‘downhill’, ‘flat’ or ‘uphill’ x approach = ‘from a bend’ or ‘from a straight’). The site characteristics help refine the trial sites into overall categories that help with identifying suitable locations for installing PRIMEs. The knowledge gained from the research provides insights that could assist with choosing sites based on potential behaviour change results.
While a range of research questions have been addressed in Phase 1 of Project PRIME there are specific issues that need to be considered:
- Due to a specific focus in the research within Phase 1, the trial sites consisted of 18 left-hand bends and 4 right-hand bends. While there is less data for the performance of PRIMEs on right-hand bends, some evidence exists that they produce positive behaviour change. The evidence base for right-handed bends will be increased during Phase 2 of Project PRIME.
- To date the PRIME road markings have been trialled on two-lane trunk roads (divided by a centreline). Within the United Kingdom, 5.5m is the minimum overall road width for roads with centrelines. This document provides two designs for PRIME road markings based on different lane widths up to 3.5m and over 3.5m.
- The focus of Project PRIME has been in supporting motorcyclists before they navigate round a bend. As such, PRIME road markings are not envisaged to be installed on bends.
- Project PRIME has not installed PRIMEs on single-track or one-way roads and given the focus of casualty reduction specifically on rural roads which tend to be two-lane roads for traffic in both directions, more research would be required before any guidance can be issued.
- Project PRIME has not installed PRIMEs on motorways or dual-carriageways and it is not envisaged they would be suitable for these situations. It is possible that the PRIME road markings could conflict with traffic spacing chevrons and with bend radii being much greater the likelihood of motorcyclists losing control on bends is reduced
Details for the characteristics of each trial site is provided including information about the speed limits and 85th%tile speed surveys (see: Appendix C).
Where did PRIMEs work best?
With 32,213 motorcyclists observed, the following statistically significant results were observed for rider behaviour:
- speed reductions at 10 trial sites
- positive changes in lateral position at the final PRIME gateway marking (closest to the bend) at 15 trial sites
- positive changes in lateral position at the apex of the bend at 13 trial sites
- reductions in braking at 9 trial sites
- increased use of PRIME road markings by motorcyclists across 18 of the 22 trial sites
The findings from Project PRIME Phase 1 provide an indication of potential behaviour change effects that might be observed on bends with similar characteristics (Table 1).
| Characteristics (Speed - gradient - approach) | Number of sites | Speed | Position at PRIME | Position at Apex | Braking | Gateway |
|---|---|---|---|---|---|---|
| Slow - downhill - from a bend | 1 | NA | Sig | NA | NA | Trend |
| Slow - downhill - from a straight | 1 | Sig | Trend | NA | NA | Sig |
| *Slow - flat - from a bend | 2 | Sig | Sig | Sig | Sig | Sig |
| *Slow - flat - from a straight | 2 | Sig | Sig | Sig | Sig | Sig |
| Slow - uphill - from a bend | 1 | Sig | NA | Trend | Trend | Trend |
| Slow - uphill - from a straight | 2 | Sig | Trend | Sig | Sig | Sig |
| Fast - downhill - from a bend | 2 | Sig | Sig | Sig | Trend | Sig |
| Fast - downhill - from a straight | 2 | NA | Sig | Sig | Sig | Sig |
| Fast - flat - from a bend | 1 | NA | Sig | Sig | Sig | Sig |
| *Fast - flat - from a straight | 4 | Sig | Sig | Sig | Sig | Sig |
| *Fast - uphill - from a bend | 2 | Sig | Sig | Sig | Sig | Sig |
| Fast - uphill - from a straight | 2 | Sig | Sig | Sig | Trend | Sig |
Table 1 provides an overview of the results for each of the twelve site categories. The following legend is used:
- * – indicates the sites where most behaviour change was observed
- Sig– statistically significant results for behaviour change observed
- Trend – trends in the data observed (i.e. not statistically significant but almost)
- N/A – no behaviour change was observed
These results represent the combined results across all the sites in each category. It is possible that where significant results are shown for measures these were not found across all sites in that category. For individual site results please refer to the research reports (see: Appendix D).
The information above may assist anyone looking to install the PRIME traffic sign and road markings to consider where they might be most beneficial.
From Phase 1, the results indicate that PRIMEs delivered the greatest behaviour change at the following sites with statistically significant results across all the measures:
- slow – flat – from a bend
- slow – flat – from a straight
- fast – flat – from a straight
- fast – uphill – from a bend
At these sites a range of encouraging results were observed:
- slow – uphill – from a straight
- fast – downhill – from a bend
- fast – downhill – from a straight
- fast – flat – from a bend
- fast – uphill – from a straight
The fewest results for behaviour change were observed at the following sites:
- slow – downhill – from a bend
- slow – downhill - from a straight
- slow – uphill – from a bend
It is important to emphasise that even at sites where less evidence of behaviour change was observed, there were no instances recorded of negative behaviours arising from the installation of PRIMEs. This provides evidence that PRIMEs did not have a detrimental effect on rider behaviour at the pilot locations.