Auxiliary power units, otherwise known as APUs are used by a sizeable amount of truck drivers to help limit fuel use since they exclude the need to run trucks engines on idle while parked. But seeing as they typically weigh a few hundred pounds, they may be a problem for drivers who regularly carry close to the maximum weight limits. With the president’s recent expansion of the MAP-21 bill dealing with state-by-state APU regulations, this may be confusing to drivers crossing state lines.

Below, vehicle satellite tracking company Track Your Truck positioned a guide that can inform drivers exactly how much weight is exempt in each state.

Check it out:

APU Exemption Guide

APU Exemption Guide by Track Your Truck