If it's the latter, then you could only check for collisions if the object moved in the last game loop
Hmm... the trouble I have is that when blocks are pushed against each other, blocking the path for example, I want the player to be able to push one block and have the others continue along the conveyor so this method will not work (as the block was stationary).I suppose I *could* store the information of which blocks are on which conveyor and only update those which have blocks on them to save a few frames, but it still requires me to cycle through each of the special tiles multiple times.