Today, I had an idea:
Add trailers that appear in certain areas and that we could hang in the back that some vehicles. This would carry more things! To repair we need 2 wheels and 1 scrap metal. We could tie them at the back of the car with a hooking ball with a option from the driver. (like the tow truck or ferry)
example : http://i.gyazo.com/6652ea7d0491b871b308464343a093c9.png
PS : Sorry for my bad english i'm french
