EDR's have been around for about 10 years. I learned about them at a Seminar on neck injuries and CAD injuries 10 years ago. They are not "commonly" used as most are not aware they are even there. The "black box" is constantly being overwritten (about every 30 seconds) until there is an airbag deployment at which point it stops recording. Can be used if there is a primary then secondary collision to determine who hit who first. Obviously it is recording speed too.