So far conveyor belts can go through the ground and through other belts. In addition, the items they carry can go through all these things as well. It would be really nice if they were more than just textures for this matter: to be impossible for them to go through others and through the ground. In addition, it would be super awesome to extend this to the items they carry, so you would have, for instance, to take into account the size of the items carried before having a belt over the another one.