I already tried a tractor trailer and a tow truck towing a RV, lol, but it's very hard. The trailer is easy lost on some of the bumps, and the tow truck has a tendency to get pulled off by whatever its towing. Good luck, I'll keep working on the tractor trailer, done like 15 attempts so far and never got further then 1/3rd up. Small tip: you don't want to roll off a mountain with the ron tanker, lol.
btw, this kinda stuff is what I like doing in MP too
oh btw, if you think dfriving up the mountain is hard, that last bit over the stairs to the observation platform took me like 20 minutes to get over it.