if there are tanks on the road, I like to use what people have said here and change the Height of Function on the bomb and drop ahead of them.
However, if the targets are soft (trucks, APCs, etc) in a column moving along a road, I like to turn off the PAC system (flip the gun arm switch down) and let the recoil of the gun guide my aim along the road with the burst length depending on the number of vehicles. This is very effective as the gun fires around 70 round per second so it's hard to miss and more reliable than using CBUs, at least against soft targets.