Likely I read this story in OMNI Magazine or Isaac Asimov magazine in high school (1981-1985). I remember it involved people either travelling through time or teleporting but ethically they were not allowed to mess with people or affect them permanently (or change the future if it was time-travel related). The loophole was that if a person was going to die anyway, they could mess with them. so the characters found a person who was going to drive over a precipice due to a washed-out bridge and die anyway, so they were appearing in front the vehicle to freak the driver out, but then the vehicle plunged over the precipice and the person died so it didn't matter anyway. But... of course something goes wrong (I forget what). Tracked down a few others I remember such as Ray Bradbury's "A Sound of Thunder", which I read in the same era, so could have been in anthologies or reprints.