Executive summary
The Highways Agency wish to establish whether current best practice standards for PPE are adequate to ensure road worker conspicuity under night time and daytime conditions.
The HA commissioned TRL to carry out research focused on the following research questions:
1. What are the perceptions and opinions of road workers with regard to their conspicuity?
2. At what distances are road workers seen in a naturalistic but controlled track study under daytime and lit/unlit night time conditions2?
3. Do different colours of PPE vary in their visibility under daytime and lit/unlit night time conditions?
4. Are there differences between subjective ratings of visibility for different coloured materials (representing PPE) against different background colours (representing works vehicles)?
5. What are the expectancies of drivers regarding the likelihood of encountering road workers in the proximity of vehicles stopped at the side of the road with flashing lights or beacons?
In addition, when the project was underway, the team were asked to comment, if possible, on any differences apparent in those participants with colour vision deficiencies.

The research consisted of the following activities:
1. Consultation with road workers about their perceptions of conspicuity.
2. Track studies during night time and daytime conditions, in which participants were driven past one of two mocked-up scenarios on the TRL track, and asked to comment on the things that grabbed their attention. This was designed to measure detection distance of PPE-wearing mannequins under relatively naturalistic driving conditions.
3. A study in which participants rated the subjective visibility of difference combinations of PPE material and background colours.
4. A post-drive interview in which participants were asked about their expectancies on encountering vehicles with flashing lights and beacons in their everyday driving.
Conclusions
Road workers are not highly conspicuous, even in hi-viz PPE
The first conclusion of this report is that road workers are not as conspicuous as has been observed in previous studies that used =search‘ instructions, especially at night. Detection distances of as low as 25 to 45m were observed in some night time conditions.
It is highly likely that road workers in general are not aware of this and are likely to over-estimate their actual levels of conspicuity.

Conclusions:
Drivers do not necessarily expect to see road workers
There was no obvious „overall? impact of different types of PPE on detection distance
Ankle markings and fluorescent trousers would be advantageous
White may be the most appropriate vehicle colour at night, and orange PPE against white vehicles may be the easiest to see
A number of recommendations are made.

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