True but there is the opposing force where if you live ten times longer, and you don't have to do the driving, its just as "effective" to sit in the back of some kind of conversion van going 5 MPH playing video games or reading or sleeping than to drive at 50 MPH.

There is a justification for raising speed limits even if death rates increase slightly because the aggregate total loss of life at 55 might be higher than at 65, assuming loss of life due to sitting around driving is as bad as loss of life due to being dead is equal. On the other hand if you live "forever" and you're not doing the driving anyway, then its hard to justify going more than 10 MPH or so. At which point its probably about 8 times less bandwidth required at 10 MPH than 80 MPH.

Its also more economical WRT gas or solar electricity use or whatever propellant solution.