01-08-2012, 02:52 PM
SKID RESISTANCE TEST
BACKGROUND
Skidding, i.e. loss of adhesion between a vehicle's tyres and the road surface,
occurs in many road accidents whether or not it is the actual cause of the
accident. Over the years, tyre manufacturers have done a lot of research into
different types of rubber and tread patterns to improve the safety of motor
vehicles. Governments have introduced regulations concerning the tread depth
and general condition of the tyres. Highway engineers have also researched ways
to improve the skid resistance of road surfaces. The impetus for this research
came from the Transport and Road Research Laboratory (TRRL) of UK. One of
the first things they did was to devise the Pendulum Skid Tester which, being
portable, can be taken to the site or used in laboratory experiments. This device
simulates the skid resistance offered by a road surface to a motor car travelling at
50 km/h. It gives a number, being a percentage, somewhat akin to a coefficient of
friction. Subsequently, they devised the Sideways Force Coefficient Routine
Investigation Machine (SCRIM). This is a lorry with a fifth wheel set at an angle
to the direction of travel and the lateral force on this wheel is measured and
recorded. The lorry travels at 50 km/h and continually monitors the Sideways
Force Coefficient (SFC).