As you progress through Outbound you’ll find four landmarks to visit with mini puzzles attached to them. The third one is the windmill, but to reach it you’ll face difficulty as it’s up a steep slope. In order for your vehicle to go up slopes, you’ll need to upgrade your motor. This requires researching the motor upgrade and then crafting it, but it’s not immediately obvious how to do this.
After searching for a while you might be losing hope, but there’s a simple solution. You’ll need to drive to as many signal towers as possible and use download coupons at each of them until the option to download the vehicle research station becomes available. For us, this was 12 signal towers, but it may vary for you based on the other options you’ve chosen at signal towers beforehand.
Once you’ve downloaded the vehicle research station blueprint, head back to your camper and enter building mode. Place the vehicle research station on a counter in your van, and from there you’ll see branching options with multiple upgrade choices. For the motor upgrade, you’ll need 10 bolts. These can be crafted out of scrap metal at the bolt press machine.
Once you’ve crafted the motor upgrade, you’ll be able to get up steep slopes to access the remaining landmarks.