It's not so much a latency issue but a field of view issue. Cars don't really go that fast and you'll see them coming way ahead of time as long as your camera is zoomed out far enough. There are procedures in place to reduce the amount of stuff like this happening, but they haven't always been in place and they don't work 100%. But it's not like it's an issue that nobody has ever thought of, it was happening even before the rise of the drones: http://en.wikipedia.org/wiki/Grdelica_train_bombing