The impact of modern asphalt on motorcycle road safety

July 21, 2009

Motorcycling can be fast, furious fun, even for the over 50s but it is also dangerous; over 50 times more dangerous than driving a car!

Statistics collected in the UK show that while the average age of motorcyclists has increased, their safety track record has improved only marginally in recent years. Rather than the pursuit of young tearaways, motorcycling is conducted by mature individuals who are also quite likely to own a car. While statistically they like to live dangerously once in a while, the research suggests they would prefer to get from ‘A to B’ in one piece and remarkably few claim to be reckless speed addicts.

In fact, ‘human error’ remains the main cause of death and injury but poor road design and surface condition can be contributory factors. Motorcycling associations have shown widespread concern about these issues and highways authorities across Europe have come under attack from the Federation of European Motorcycling Associations (FEMA). FEMA has even accused engineers and maintenance staff of being unaware of the hazards presented to riders.

In the European Agenda for Motorcycle Safety, FEMA highlights several problem areas which it feels require more attention. These include lack of friction of some asphalt types when wet, poor drainage which increases the risk of aquaplaning and bad kerb design. Bituminous asphalt sealers, potholes and the rutting caused by heavy lorries are also singled out for criticism. The biggest problems are, as might be expected, with older highways.

Specialists within the CEMEX UK technical team are well aware of these issues and point out that good design and construction practice ensures highways are safer for all users, not just motorcyclists.

Roads are created by building up layers of different types of coated stone. Basic construction comprises sub base, base, binder course and the surface or ‘wearing’ course. The base courses have larger diameter aggregate to help withstanding the heavy loads and to ensure the underlying ground is not subjected to stresses from the traffic. Modern surface course formulations, such as stone mastic asphalt (SMA), are able to resist the rutting often seen - and felt - on the inside carriageway of major roads. The final surface layer can be comparatively thin and formed using sizes and types of aggregate that provide very good grip, even in wet weather, which is imperative for the motorcyclist.

When correctly applied, these thin surfacings - including Viatex and Viapave from CEMEX’s ‘Via’ range - are also resistant to wear, which means fewer cracks or potholes develop and less remedial work is needed between re-surfacing. Historically, it is the remedial ‘overbanding’ with bitumen used in crack repairs and repairs to joints between running lanes that creates small, smooth or ‘slick’ areas. These areas can catch out the unwary motorcyclist, especially in the wet. Under some conditions these patches are just as hazardous as the unfilled cracks as this may undermine the motorcycle and its rider.

In the past road builders relied on hot rolled asphalt or macadam (sometimes tarmacadam, Bitmac or - incorrectly - just tarmac) as the mainstay for road construction. The more recent additions to the ‘blacktop’ list such as thin surfacing systems such as CEMEX Viapave and Viatex, coupled with a range of proprietary brands, mean it is possible to design each road specifically for the type and amount of traffic it handles, particularly where heavy goods vehicles are concerned.

Take a 2km section of the M9 in Sterling, Scotland for example. This contract was one of the first to be carried out by CEMEX Surfacing to newly introduced specifications aimed at improving the durability of roads. This was achieved in part by sealing the road against water through techniques such as edge compaction; using an edge roller helps to close any voids left through the traditional method of ‘cutting back’.

Detailed planning of all aspects of the project included staggering the joints, painting all joint faces, over-band sealing of the lower base and binder course layers and placing a tack/bond coat between all layers to stop water penetrating the road. Ensuring water runs off the road, not into it, is an important factor in reducing the problems highlighted by FEMA. While potentially uncomfortable for the car driver, these faults tend to be little more than inconvenient for the motorist but can be a significant hazard for the motorcyclist when they result in the appearance of potholes in the surface of the carriageway.

In total, 34,000 tonnes of material was removed on this section of the M9 and the carriageway was reconstructed with 11,000 tonnes of recycled sub base and 23,000 tonnes of bituminous material. While safety is paramount, with this volume of materials and the design of the materials installed (such as CEMEX Viapave and Viatex), improved road pavement durability and longevity also gives financial benefits.

Motorcyclists can justifiably claim their machines impose very little wear and tear on road surfaces; however it is paramount in terms of safety that the motorcycle tyres have as much contact with the road surface course layer particularly in wet weather. With the possible exception of noise pollution, motorbikes are an eco-friendly form of transport. The steady expansion in motorcycle traffic can therefore be seen as a welcome trend. But with an average of over 6000 motorcyclists killed or seriously injured each years on British roads there is an obvious responsibility for all those involved in road building - from the planner to the asphalt supplier - to consider their particular requirements.