As tyres wear during a race, the rubber that falls away collects of the racing line to form ‘marbles’ which are very slippery should the car find itself on them.
Marshal
Marshals are positioned at many places around the race circuit, their job is to look after safety. This includes moving cars from unsafe positions and alerting drivers to on track hazards by waving various coloured flags.
Monocoque
A modern F1 chassis is known as a monocoque, this construction of carbon fibre composite means is a one-piece construction designed around the driver. In affect the driver sits in the car much like he does in a bath.