What is a skid mark?

Some of you will be thinking a skid mark is tyre rubber left on the road surface following a skid. Well, it is actually a mark left on the road caused by heat that has burnt the oils and grime that is on the road. When a vehicle skids the tyres heat up, the friction of the tyre(s) locking and skidding in turn burns the oils on the road.

Skid marks are used by the police following a crash to determine things like the speed a vehicle(s) was travelling prior to a collision. However, it not just the police that can gain useful information from a skid. Drivers could use skid marks to identify potential hazards.

Imagine you are driving along a straight road in the country and you see a skid mark ahead, you could either ignore it as not relevant or, if you are a good driver, you would be thinking ‘why did that vehicle need to brake so hard?’ Is there a hidden entrance? Is it where a foot path or bridleway crosses the road? Is it a narrow country lane? If it is, look at the edges of the road. If the edges are damaged, is it because large vehicles use the road? If so, have the skid marks have met each other?