There are electronic devices that you can buy that will essentially monitor the car’s speed and the force of braking. These devices keep a record of driving behavior, and can be checked after he drives, in order to find out how he operated the car.
Tell your son that these are the terms, without compromise:
If he disconnects the device, he will lose his driving privileges for 30 days.
If the device indicates that he has been speeding and/or doing very heavy braking, he will lose his driving privileges for 30 days.
If he is found to be driving recklessly a second time, he will lose his driving privileges for 60 days.
As a retired school counselor, I can tell you that getting the desired behavior from an adolescent involves finding the correct leverage point. With a 16 year old, one of the two strongest leverage points is loss of driving privileges.
Good luck!