A Class 1 driver sees snow buildup on the trailer roof, a low-clearance warning ahead, and a route with an unmarked canopy near the delivery point. Which planning principle best applies?

1. Know the vehicle height and account for environmental factors like snow, ice, debris, tree limbs, utility lines, canopies, and roof overhangs before proceeding
2. Assume posted clearances always account for snow on the vehicle
3. Proceed because roof snow reduces vehicle height
4. Ignore unmarked objects if the route is short