I always taught to avoid Highways/Interstates unless it's the only option. Just as mentioned above, planes are designed to take vertical impacts from landings, but you put them head-on or rear-ended, they are going to be destroyed with you being a crash dummy. You can land most single engine 4-seaters in a very small footprint if you practice power off landings often.

As far as theories for landing on a busy road, I think setting an approach speeed is very important, use an upwind leg to determine wind, so then if you can make a "pattern" you know what airspeed to use. Flying slower than the pace of traffic if at all possible when you get below 500'. You do this, people catching up to you will see you(hopefully) and then slow down, vs coming up on top of someone that would have no idea. Making yourself visible to the traffic by doing a high/long final over top so folks start noticing you. Wagging the wings very obviously(maybe to the onlooker you would probably be percieved as out of control). Using your landing lights, just about anything you can to increase your visibility to others.

There's probably 100+ ideas, just hope no one has to ever use them!