I added a police car laying in wait on the upper left turn of High Speed. It's a 1:42 scale Ford Crown Victoria, a good representation of a police car of the 80's with lots of great detail. It's die cast but a bit larger (5") than a Hot Wheels car.
To mount it, I removed the bottom rear screw of the car and fashioned a piece of scrap metal from my tool box and attached it to the bottom of a car with a slightly longer screw and split ring lock washer. The other end of the metal is slightly bent downward and attached to the existing far rear corner using the existing screw that holds the plastics in place.
Quick and easy 10 minute mod. Car found on Ebay is this one:
http://www.policecarmodels.com/ki1fopocar.html