All newly manufactured passenger vehicles after September 1, 2014 are required to include an event data recorder ("black box").
What does it do? It collects data on a loop, meaning that the last 30 or so seconds are continuously recorded and then overwritten with the latest information.
Information includes
Vehicle Information
Vehicle speed
Engine speed
Throttle position
Brake switch circuit status
Actuation of antilock brake system
Driver Information
Driver and passenger seat belt status
Air bag suppression switch status
Ignition cycle
Driver and passenger seat position
amongst many other data points
This collected data allows agencies to (such as NHTSA) to evaluate the performance of vehicles in crashes.
Though what will the data be used for in the future? Can it provide evidence to incriminate drivers or the vehicle manufacturer themselves?