larger in order to account for both displacement of the payload 14 due to the different grades the truck 10 may traverse and vibrations even with a larger bed 13 the payload 14 should be correctly placed on the bed 13 not too close to the rear 15 of the bed 13 and not too close to the front end 16 of the bed 13 or spillage may still occur as shown in fig1 the payload 14 was deposited onto the bed 13 at or about the position 18 as shown in fig2 the payload 14 is loaded closer to the front end 16 of the bed 13 to limit spillage off of the rear end 15 of the bed 13 when the truck 10 is proceeding up the grade 111 as a result the operators that load the truck 10 may take into consideration the highest grade 111 that the truck 10 needs to traverse and exercise the judgment to properly place the payload 14 on the bed 13 to limit spillage over the rear 15 of the bed 13 to reduce the amount of judgment that operators must exercise fig3 illustrates a technique for loading the bed 13 while the bed 13 is in a tilted position shown by the angle u03b1 in the example shown in fig3 a tilt support mechanism 20 is employed.