Chevron Quality in Fog and Rain – The Importance of Visibility Distance

On British roads, rear chevrons which look bright and clear on a sunny day must also be visible in fog, in the wet and in spray that blinds drivers. When works vehicles stop on live roads or travel slowly, good chevrons matter most.

What Chapter 8 chevrons are for

“Chapter 8” refers to the part of the Department for Transport’s Traffic Signs Manual covering traffic safety measures and signs for road works and other temporary situations on the highway. It includes guidance on high-visibility rear markings, typically red and fluorescent yellow chevrons, for slow-moving works vehicles, such as highway maintenance vehicles, recovery vehicles and utility vehicles that operate on or near the highway. Their purpose is to make slow-moving or stationary vehicles as visible as possible to drivers approaching from behind.

For Chapter 8 Chevrons, visit www.vehiclechevrons.com/

The problem with low visibility

National Highways advice on driving in fog.

Driving at 70mph means that you are travelling about 31 metres per second. This means that when driving through dense fog you will have less than a second to react to objects in front of you. National Highways advise the use of headlights when visibility drops below 100m, and the use of fog lights only when visibility is seriously reduced. Heavy rain and the spray from other vehicles can also drastically reduce visibility. In these circumstances the rear markings of a works vehicle can be the first thing that an approaching driver sees.

Why material quality matters in the wet

Chevrons are made from retroreflective sheeting which allows light from a car’s headlights to be reflected back to the driver. Not all retroreflective materials are created equal and lower grade types of retroreflective sheeting can lose much of their retroreflectivity when wet, dirty or worn.

Higher-performance microprismatic sheeting contains many small prisms that collect and direct light towards the driver efficiently across a wider range of angles. This means that good quality products will continue to function in wet weather, and also be more visible in daylight and at dusk due to their fluorescent colours.

The Science of Rain Visibility

Water droplets on a reflective surface scatter light in many directions so less of it is reflected back to the driver. The same applies to fog and spray in the air. A brighter, well-maintained reflective material will provide drivers with more warning, so they have more time to slow down or move over.

Keeping chevrons effective

• Choose chevrons that meet the guidance and specification your client or highway authority requires.
• Clean them regularly, as road grime greatly reduces reflectivity.
• Replace chevrons that are faded, scratched, peeling or damaged.
• Check that nothing, such as a tow bar or equipment, blocks them from view.
• Combine them with correctly used beacons and lights.

Frequently asked questions

Do all vehicles need Chapter 8 chevrons?

No. They are designed to be used by vehicles that operate on or near the highway, such as maintenance, recovery and other utility vehicles. They may be mandatory depending on the type of work being undertaken, on which road, and the requirements of the highway authority or client, so check the guidance that applies to your operation.

How often should chevrons be replaced?

There is no single interval. Replace them when they are damaged, faded, peeling or no longer reflect brightly, and follow the manufacturer’s guidance on expected life. Regular cleaning and a visual check as part of vehicle inspections help spot problems early.

Where to go next

For more on keeping vehicles safe and roadworthy, read why electric vehicles fail their MOTs in unexpected ways.