Surface dressing is a cost-effective maintenance technique to stop roads in relatively good condition from getting any worse. Surface dressing seals the road to prevent water getting in and cracks and potholes forming. It also helps to make roads safer, by improving skid resistance when braking hard.
First the road is patched, if necessary. Then a layer of bitumen, or similar, is added to act as the 'glue' before the road is topped with chippings. Driving over the road then helps to bed the chippings in. Loose chippings are swept away over the next few weeks. They're not swept up immediately because the action of traffic over a newly surface dressed road helps to bed any surplus chippings in to the surface, ensuring they're spread out to the edges and providing even coverage across the whole width of the road.
Surface dressing extends the life of a road and prolongs the need for expensive resurfacing works. Roads that are surface dressed can last from 10 to 15 years. Depending on how well-used the road is and the kind of traffic that uses it they can be surface-dressed for up to 3 times before they need to be replaced. It costs around £3 per square metre to surface dress a road.
Firstly, the condition of the road is assessed through a combination of visual inspection and other scientific techniques to evaluate the condition of the surface and the structure of the road. If the road is in a relatively good condition it will be surface dressed to keep it in a condition that is acceptable for the majority of road users.
Usually, when a road is being surface dressed it doesn't need to be closed, although access may be limited for short periods of time. If it's a busy road there may be some temporary traffic management, such as stop and go signs.
Surface dressing is usually completed at each site within the day. Depending on how busy the road is and how quickly the chippings bed in, loose chippings may be swept up on several occasions for approximately one month. Line markings and cats' eyes are replaced after then.
The surface dressing season is between about April and September. Surface dressing can only be done in the summer as the warmer weather is needed to help the chippings bind to the bitumen. Also it's less likely to rain, meaning the bitumen and chippings will bind to the road surface better. Work on busier routes doesn't usually happen at peak times.
Resurfacing is more extensive structural maintenance. It can involve removing several centimetres of worn out road surface and replacing it with new material and rolling it out to give a smooth surface.
If a road has deteriorated too much – the fundamental structure of the road is in too poor a condition – it will be considered for resurfacing or more extensive work when the road can be made a priority for funding.
Resurfacing takes much longer. Often the road has to be closed completely and traffic diverted meaning longer journey times and potentially more congestion.
Driving advice on newly surface dressed roads
We try to maintain access for residents as much as possible but there will be short periods where we cannot. If there's a particular reason when access is needed at a specific time you should speak to the gang on site who will usually be able to accommodate residents' needs.
As the highways authority, legally we have to put up signs advising motorists of road works and any action they should take to reduce the risk of damage. This means we're protected against any claims of damage to, for example, chipped windscreens or paintwork.
Signs are put up in advance of surface dressing or resurfacing work starting. We also deliver a letter advising of work and containing contact information to properties that front the works.
Advisory notices are also placed along routes to be surface dressed telling drivers there is a risk of skidding and that a maximum speed limit of 10mph should be observed. There should not be any damage to vehicles if drivers follow this advice.
Read more our programme of improvements to the county's roads.