Personally, I think accelerometers should be included in the package, with their data recorded along with speed infractions. The package should also include a device to determine if the vehicle is tailgating. It should also be wired to determine how turn signals, brakes, and the accelerator are used. The total package would not only be able to determine if a vehicle is speeding, but also if it is weaving, sliding, peeling out, tailgating, if it isn't using turn signals, and does Texas stops. The data should go to the State, but not for enforcement purposes (except in case of accidents, and/or suspected criminal activity). The States should share the data with all auto insurance companies, first and foremost. Auto insurance companies would then use the data, to determine what each individual should pay for auto insurance. The data could also be used to help determine life, health, and disability insurance rates. The data should also be given to lawyers and law enforcement, in case of auto accidents, to help determine who's at fault, for civil and criminal purposes. The vehicles owner should also be able to access the information.
If the device determines it's likely the driver is driving recklessly, drunk, or impaired (for whatever reason), the engine should turn itself off, the first time the car comes to a stop. A code would have to be entered into the onboard computer, by an agent from your insurance company (for a fee), in order to restart the car. Of course, law enforcement would probably have an eye out for cars that won't restart at intersections, breatholizer in hand.
Actually, law enforcement should probably be notified, so they can help with traffic problems, around the stalled vehicle.
In New York State, auto insurance is capped, for high risk drivers. All the other drivers are subsidizing the high risk drivers auto insurance, through higher rates. I believe this should be changed, so that everyone's driving habits determines the amount they are charged by insurance companies. No caps and no subsidies. Auto insurance should be manditory in all 50 States.
This would allow people to drive fast, even if it's against the law. But, it would be reflected in their auto insurance bill. Wouldn't make speeding legal though, and law enforcement would still be out there patrolling, and able to pull you over for any traffic violation.
EDIT: Insurance companies would determine how the device is programmed, in order to determine if the vehicle is being driven recklessly, or by someone drunk or impaired. The vehicle owner could shop around for insurance.