Some guy figured out that if you hold up at the beginning of the game before you are dropped onto the road, you will zoom up the side of the screen out of bounds. The death I take is intentional, if you stay on the same line you start off on, cars will ram you off the road or you will eventually crash, so dying in that spot means you can reset the line further out to the right. It is the easiest speedrun on the NES, but I'm pretty happy with it because I had to find a new glitch to get this time. I realised that pushing up would sometimes give you a little speedboost, and it took me a while to figure out why. Every time a dark blue car appears on screen, you can push up when it is at a certain part of the screen and get a speedboost.
The game has no end so one full loop of the map is considered as completion.
Are you just constantly mashing right to do that or something? I never played the game so not sure what's totally going on