[jacquesm]

A stationary car bomb has a lot of advantages over other assassination methods. For one it allows you to get away, you only need to plant the thing and it could go off hours, days or weeks later. The assassin could be a in a different country when the bomb goes off. You could put more of them at strategic points into a city not knowing anything about the daily routine of your target, just their license plate would be enough. You could drop a bunch of them ahead of time in random places and program all of them by remote to scan for new plates and so on. Not much you could do about it either, every parked car would be a risk.

[woodman]

I'm guessing that you're concerned about a place that has no parking authority, highway patrol, corporate security, nosey neighbors - because an abandoned vehicle won't last more than two days otherwise. There is a reason why assassins have historically chosen guns over bombs, and it isn't due to a lack of technology that places distance between themselves and the target. Like most important things, when assassinating somebody, you want to eliminate as much uncertainty as possible. That is pretty much the opposite of just leaving a bomb somewhere and crossing your fingers. Also, leaving a lot of bombs all over the place increases the odds of detection.