In the built in campaigns, the vehicles smoothly follow the roads, and never slow down when they turn.
When I set up a number of waypoints along a road, the vehicle will follow the road for a bit, steer away from it, go in some weird direction for a while and then go cross country for a while, and then maybe get back on the road towards the next waypoint, even if it's along a straight.
And say for a patrol path for a tank, at each waypoint, it stops completely for a few seconds, before turning and going again.
What can I do to prevent this, and get the smooth movement from the built in missions?