A slippery business

26 Feb 2024

Increased Risk of Accidents in Rainy Conditions

Drivers are more likely to skid in wet weather than in dry weather. This is due to the lower friction coefficient of tires on wet roads. "A hard stop at 80 km/h on a dry road results in a braking distance of about 31 meters for a car; in the wet, this increases to 50 meters and more,” says DEKRA tire expert and accident researcher Christian Koch.

The lesson to be drawn? The motorist needs to drive more carefully and increase the distance to the vehicle in front if the road is wet or damp

Christian Koch
In curves, in particular, a less energetic driving behaviour is required. Apart from lower deceleration longitudinally, the generated lateral forces are also lower so that a vehicle can more easily depart from the road surface. Moreover, rain can also considerably restrict the driver’s vision. According to the Federal Court of Justice, 80 km/h on the motorway can be too fast in heavy rain.
Dimmed headlights even in daylight in order to ensure that motorists are easily recognisable for other road users, the road traffic regulations also stipulate that they must drive with dimmed headlights if visibility is greatly reduced, and this also even applies during the day. Visibility can be affected by rain, fog or snowfall. Court judgements deem greatly reduced visibility as just 80 meters, and on highways merely 150 metres. Should visibility worsen still further, the well-known rule comes into action for rain and fog: visibility of less than 50 meters equates to a permitted maximum speed of 50 km/h, even on highways. This also includes an overtaking ban for vehicles over 7.5 tons.
Aquaplaning is a real danger if the water cannot swiftly flow away from the road surface and begins to collect in recesses such as tire tracks. Already at around 80 km/h, worn tires can build up a wedge of water and make the vehicle unsteerable. “When this happens, immediately reduce your speed, depress the clutch and whatever you do continue steering in a straight line until the tires finally grip – and obviously continue driving at a slower speed,” reminds Koch.