Designing curves for safety: Cant, camber or super-elevation, is the difference in elevation of two road edges. Designers ensure that a curved road is sloped so it is higher on the outside of the curve. Super-elevation allows part of a vehicle’s weight to assist in maintaining a circular path. It reduces the required amount of side friction between the tyres and road surface when driving a circular path. This is important for the safety and comfort of all road users. The amount of super-elevation depends mainly on the operating speed of the curve and the curve radius, with more super-elevation applied on tighter curves. However, with the need to drain water off the road surface there is a minimum amount of super-elevation applied to all curves.
There are many factors limiting how much super-elevation to use, including:
- stability of high laden commercial vehicles
- stability of loads on trucks
- tendency of the rear wheels of slow moving vehicles to track towards the centre of the turn
- appearance, particularly in flat terrain and in urban areas
- effect on out-of-control vehicles leaving the inside of the curve
- tendency of vehicles to slide on the road surface in frost/icy conditions
The curve radius on the bend in the vicinity of my property is about 60metres the super-elevation is practically none existent.