Here is a piece of interesting info that could possibly be used in a scene:
In some states, if you dial #77/*77 you can reach a police dispatcher. If not, call 911.
There have been instances reported of people being pulled over by unmarked police cars who end up not truly being officers. Most often, they are rapists trying to attack female drivers, but in some cases they could be criminals looking for a different mode of transportation, or attempting to rob the drivers. They say it is always recommended to keep driving to a safe area if you are pulled over by the police, especially if its unmarked and in a lone setting.