What is ‘Superelevation’?
Most roads are ‘Crown Cambered’ that is, they are higher in the centre than at the edges to allow water to drain towards the kerbs. However, Motorway bends are ‘Superelevated’, which means they slope gently from one side of the Motorway to the other across both carriageways. In a right bend, the slope is relatively high on the left sloping down to the to right and in a left bend it is relatively high on the right sloping down to the left; as viewed in the direction of travel.
What advantage does this give? In a bend, a car is acted on by the Corner Force, which points towards the centre of the bend. Corner Force destabilises the car and, wherever possible, needs to be kept to a minimum. We do this by applying SYSTEM on approach to a bend. I.E. we maximise the bend radius by keeping as far left as possible in a right bend and as far right as possible on our own side of the road, in a left bend: in each case, only if it is safe to do so. We approach the bend at an appropriate speed as determined by the Limit Point and the Safe Stopping Rule.