I have removed mountains from my random gen maps. I regret this. I like having them but the gravity mechanic forces me to a stop three quarters of the way up a steep road. I can empty the vehicle inventory and carry it up. If I have more in there than I can carry, it's a royal pain.
Even the hills I get without mountains slows me to a crawl.
Can I tweak with the vehicles to get me over the hump?