It isn’t much, but it is the fleeting hospitality of New Yorkers, each jealous of his privacy in the crowd. Ever helpfulness is often delivered as a taunt: a man, rushing the traffic light, shouts the man behind him. “ You want to be wearing a Buick with Jersey plates?” — great scorn in the word Jersey, home of drivers who don’t belonghere. That’s it
The man is warning the other driver that his actions may cause an accident. If the car in the back collides with the car in the front then the two cars would be so crushed and attached together that it could look like he would be wearing a license plate. In this case, one of the cars was a Buick with a New Jersey license plate. It's called a rear-end collision in English.