Shifting to R to RACE

it'd just coast? That's the part i was most interested in... i was imagining an axel breaking.

Your tranny would go before anything else.

that's what I expected next... I guess I just kind of worked it out backwards... there's also the question of rear/front-wheel drive.

Wouldn't make a difference. Tranny would break before anything catastrophic would happen to anything else.

still the inertia.... something catastrophic could happen; especially on a bridge.

You're a dumbass. Transmission fails, power from engine no longer connected to wheels, wheels still roll because they are wheels, wheels without power no longer roll any faster and begin to slow down due to physics. In other words, your car would coast to a stop. Unless you applied the brakes obviously.

that's why I said inertia. If you are going 55 on the Oakland bridge and something causes your transmission to fail before you recognize wtf is going on, there is a reasonable chance you don't walk away. Things that increase your chances of dying: a truck behind you, a truck on the side of you, a cell phone, trying to accelerate as a reactionary response....

There really isn't much chance of something happening. Sure, *maybe* the guy behind doesn't notice you slowing down for some reason in heavy traffic, and if you engine stalls you won't have power assisted brakes or steering. That's about it, and only if you have an older transmission that doesn't have safety systems installed to prevent it from actually shifting into reverse while your moving forward in the first place.
Also, generally, if you accidentally do that the sound coming from you car will clue you into not doing that long before you actually do any lasting damage.