>> head-on collisions on the highways are extremely rare.

And they aren't as dangerous as many would think. Cars have done lots to improve such collisions (airbags, crumple zones). A head-on collision between cars is still two relatively lightweight objects. Hit a concrete wall, overpass support, cliff or tree and you are going up against an object that makes a care look like tinfoil. The head-on seems bad, but it is more survivable than having your car bisected around a tree trunk. Or get pulled under a big truck.