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Case Study: Britain’s Most Improved Road – EuroRAP Performance Tracking
- A404 Amersham, England


The annual British Performance Tracking results from the Road Safety Foundation show that significant reductions in the numbers of deaths and serious injuries have taken place on particular sections of road. These can involve major engineering works but many improvements came from low cost maintenance improvements and local safety schemes. This case study describes the upgrades that were implemented on Britain’s most improved road as reported in the British EuroRAP Risk Mapping Results 2014.


A404 (A413 (Amersham) – M25 J18).

Infrastructure improvements

The measures that worked were both low cost and straightforward. They included carriageway re-surfacing, improved road markings, lowering the speed limit in the built-up sections, junction enhancements including high friction surface and improving existing pedestrian crossings on a stretch where pedestrians were especially vulnerable.

Night-time visibility was also improved with new roads studs (retro-reflective pavement markers), street lighting replacement and frangible reflective bollards installed.


The infrastructure upgrades have been modelled so that an assessment of the Star Rating improvements between the two data periods can be calculated. Prior to 2010 the route was 56% 2-star, 23% 3-star and 21% 4-star for vehicle occupants. The upgrades have improved the Star Ratings to 39% 2-star, 28% 3-star and 33% 4-star for this road user group.

For pedestrians the upgrades have seen the Star Ratings improve from 17% 2-star, 62% 3-star and 21% 4-star to 56% 3-star and 44% 4-star with the 2-star sections eliminated.

The A404 between Amersham and the M25 changed from a ‘medium-high risk’ to a ‘low risk’ route (EuroRAP Risk Mapping) between 2007-09 and 2010-12 with a reduction in fatal and serious crashes from 12 to 1. The 2007-2009 crashes involved death and serious injury for vehicle occupants and pedestrians therefore the Star Ratings were analysed for both these road user types.

References: Star Rating Roads for In-built Safety – RSF

Risk Mapping Results 2014 – EuroRAP