my suggestion is to add 1 main trucking Headquarters in each active city where players must go to Collect there truck. Also to have 1 of each trailer at said location where they must attach trailer and load the cargo and deliver to random destinations throughout the city.
Special cargo could include first going to HQ to collect the truck and trailer then to collect the cargo at a random location and also deliver to a random location because the reward is much higher.
Maybe even make trucking a full time job duty - like cops/medics/firefighters/mechanics/prostitutes.
just my suggestion to make trucking a little more interesting.