The behind a vehicle is one of the most common causes of collisions while

The blind spot behind a vehicle is one of the most common causes of collisions while backing up.

Explanation:A blind spot in a vehicle is an area around the vehicle that cannot be directly observed by the driver while at the controls and this can be alleviated by the use of adjustable mirrors.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .