Every year there are numerous serious accidents on motorcycles and mopeds in Sweden, due to diesel spillage from lorries and buses. Diesel on a dry road surface means that the friction will be as low as on a road with packed snow. This is shown in a friction test ordered by the Swedish Motorcyclists Association (SMC).

Every day huge amounts of diesel are spilled on our roads, both by mistake and by carelessness. This leads to unexpected spots with friction as low as on a winter road. Most common places for slipperiness from diesel are horizontal curves, ramps and roundabouts – which are the places where powered two-wheelers have the highest need for good friction. European statistics show that ten percent of all motorcycle accident are caused by diesel spillage.

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A friction test made by an expert from the WSP Group shows that the road friction is halved when diesel is spilled on the road. The road friction before the spillage varied between 0,75-0,80, which are normal and good values. However, after the spillage of diesel on the road the friction was only 0,30, which is clearly under the minimum friction level that is demanded on Swedish roads (0,50). A road friction level of 0,30 is comparable with riding on hard packed snow and winter conditions. The low friction causes not only instability for powered two-wheelers, but also much longer braking distance. No rider of motorcycles or mopeds can be able to expect these kind of slippery road conditions during summer. Thus, it is simply impossible to foresee and adjust your riding to this, which means an increased risk of accidents.

One common reason for diesel spillage is that fuel tanks on heavy vehicles are overfilled. The overflow pours out when the vehicle enters a curve. You can often find tracks of diesel on the exits from bus garages, from gas stations for heavy vehicles and on roundabouts close to gas stations.

Winter conditions on summer roads – that is the result of diesel spillage.

SMC would like all producers of heavy vehicles to make it impossible to overfill the tank; such technique is already available. Immobilizers should be introduced that would make it impossible to start the vehicle unless the fuel cap is closed. The drivers of lorries and buses must be made aware of how the overfilling of tanks lead to an increased accident risk for powered two-wheelers.

Leaking vehicles are also polluters. All bus and haulier companies certified according to standard ISO 14001 about environmental impact, should take action against the spillage if they have not already. This is also the case for all companies certified according to ISO 39001 about road safety. Measures to reduce spillage should also be a part of the procurement made by the governmental and local authorities.

More information about the friction test can be found at the SMC website.