We have auto chains (ON SPOT) on all of our buses. They are not for heavy snow situations. They will help you get started on packed snow or ice and keep some traction. They are supposed to be able to be used at 35 mph but I don't think that is a good idea. We have to replace bearing in wheels once in a while and brass caps on pivot part of the arms. Parts are somewhat expensive but good service for us from ON SPOT. The BB factory installs them on our new buses so I don't have to. They have electric compressors if your buses don't have air brakes. Flip a switch and they are down and then flip again to retract. ED