from a thread on WHT:

Bob is driving along a highway driving his brand new Mercedes and spots his neighbour Jerry stuck on the side with car problems with his old, beat up Ford. Bob decides to help Jerry out by giving him a boost, thinking “I was in the same situation only a little while ago”. So, he stops and attaches Jerry’s car and tells him “If I’m going too fast, just honk”. So they move off, and everything is great.

All of a sudden, Marty, Bob’s evil neighbour, zooms by in his brand new BMW. Bob hates Marty and decides to race him to show him that he isn’t giving up anymore. So, he speeds up and races off after Marty, forgetting that poor Bob is tethered behind.

A police car is driving in the opposite direction and the two officers notice the three cars racing by. One policeman says to the other: “D’you see that? A brand new BMW, going at 200 km/h. A brand new Mercedes, going at 200 km/h. A old, beat up Ford, going 200 km/h and signalling for room!”