Scratching the surface for road safety

Anyone who has ever experienced a nasty skid on a dangerous bend or damaged a tyre or wheel in a pothole will have reason to be grateful for the research work being carried out by Dr David Woodward, director for the Centre of Subjects Allied to Built Environment Research at Ulster University. Woodward and his team research road surfaces and help local authorities and national roads agencies to find the optimal surfaces for their needs.

Safer, more sustainable roads that last longer and potholes that are repaired properly are just some of the areas covered. “We look at road surfaces and the role of texture in skid resistance, noise production, roll resistance and so on,” he says. “We also look at how various types of road surface materials are affected by different weather conditions.”

His work has inevitably taken him into the area of road crashes. “People don’t deliberately go out to have an accident and harm themselves or others,” he says. “There are normally other factors involved such as human error but in some cases it is clear that the road was the main cause.”

This is generally not due to poorly designed or built roads but results from wear and tear over the year, weather conditions and other factors. Woodward and his team look for ways to maximise durability and other characteristics in road surfaces in order to help reduce the number of cases where the road is a contributory factor in accidents.

Golden surface

The main challenge is that there is simply no such thing as the perfect or ideal road surface – the “golden surface”.

“I was at a conference some time ago and all the experts there agreed that the golden surface doesn’t exist, the same as the golden tyre, which would perform well under all conditions, doesn’t exist. It’s very much a case of horses for courses – you have to design the road and the surface for the conditions it will be subject to.”

Woodward explains that roads can be designed to be durable and to have other characteristics, but other factors may cause problems.

“A road surface that works well in one climate may not work for another. It may offer the desired characteristics in terms of skid resistance for example but then it rains or snows and you get potholes forming.”

Advance consultation with Woodward and his team could prevent that as well as other problems. For example, he says the Highways Agency in England is due to spend £6 billion over the next few years on renewing the surfaces on its 3,000km strategic national motorway network.

"The problem there is that they took a surface which had been developed it in Germany, transferred it to England and then tweaked it a bit to suit local conditions. But when they tweaked it the result was not what they were hoping for."

Unforeseen consequences

The English motorways had experienced problems during severe weather in the early 1990s, he says, and rather than simply continue the problem by using the same surface again, the Highways Agency looked at other European countries for a solution. Having settled on a German design the agency amended it to suit conditions particular to England but with unforeseen consequences.

"The problem was that the surface melted in hot summer temperatures," Woodward says. "This was the result of the changes they had made. They looked at the problem in Scotland and came up with a simple solution. Germany has very hot summers, hotter than England, and didn't have the problem. They went back to the original German design, as did the English agency eventually."

All of those problems could have been avoided had advance research been carried out in Woodward’s lab. “In four days we can simulate eight years of traffic on a road surface. We can look at the characteristics required for a piece of road and design the right surface to provide them.”

And those characteristics are not always the same. For example, a motorway surface designed for fast-moving traffic will be quite different to one for a small twisting country road where low speeds are desired for safety purposes. Interestingly, the weight of slow-moving traffic has a greater effect than fast moving vehicles, meaning that the surface of motorways should change for sections leading to toll booths and other slower moving areas.

Materials

“We can work with different aggregates and additives to design the surface required,” says Woodward. “

Ireland

is very lucky in that it has a good supply of high quality materials and the guys in the quarrying and asphalt industries really know what they’re doing.”

The surfaces are not the only area of research for Woodward’s group. They are also working on a hot topic for the majority of Irish motorists: pothole repairs.

“We are looking at new materials for the repair of potholes. We are working with a quick curing material which repairs a pothole very well and lasts for years. We think this has great potential.

“We are also looking at sustainability issues. Traditional asphalt is poured hot at 180 degrees Celsius, and this requires a lot of energy. We are looking at warm mix asphalt, which would have the same characteristics but would be applied at a temperature 30 degrees lower than the current type, saving a lot of energy.”