Pickups are designed to carry heavy loads in their beds. However, in rain or frost conditions, the truck may not be able to properly grip the road surface. An empty bed doesn’t provide enough weight on the rear axle for the drive wheels to hold the ground firmly. This can lead to loss of control on slippery roads. But you can avoid it by burdening the rear of the 2WD truck with sandbags, concrete blocks, or an installed load.
This article provides detailed instructions on how to achieve the desired effect and reduce slipping on the road.