I wished there could be some sort of incentive to move. I can basically hide behind a barrel forever and the game will keep running. Maybe like a timer with a distance scoring system could make this game more exciting. It would give that risk and reward to the idea of moving. I would want to keep moving as this will allow me to travel further and get a higher score. but at the same time it might be risk as the traffic light may suddenly turn red, leading to an immediate game over. Overall, I do think the stopping and hiding is an interesting mechanic and there is potential to this game.
From what I understand, there is a white distance meter at the top, though it is not clear. It is also a ridiculously long distance before you reach the end (I think). I never did reach the end.
I do agree with adding an incentive to make decisions of whether to not or to continue staying still. You are correct that you can hide behind an obstacle forever without being punished, though you technically will be punished - punished with wasting time. However, a timer would be great in making such decisions. Score could be calculated by time and distance.
I think difficulty can be increased with distance as well, as the game is too static. The UFO always so slowly turns red, and the game is too long that it gets boring without new elements. The UFO attack delay can be reduced, there could be more enemies, etc.