Slow And Stop System (sass)
(I am based in the UK London.  In the UK fixed speed cameras are quite common)

Basic idea.. When driving the car along roads with speed cameras, the speed camera will start to detect the vehicle once it passes a specified point when the vehicle is going over the given speed limit. It will then send a message in the form of a sound and/or voice to alert the driver. If this is ignored the SASS will slow the vehicle to the correct speed. The SASS can also be installed in traffic lights. Exactly the same principal, warning will be given to driver, the SASS will detect the speed of the car, and compare the stopping distance and the sequence of the traffic light. If the car is travelling too fast and there is a risk of ‘running a red light’ it will alert the driver, if it is ignored it will slow the car down and eventually stop it. 
Abdullah D 05/21/2014
This can only work as joint venture with the local authority that are responsible for the speed cameras and traffic lights. The technolgy is there. I know this CAN work!!