Off your dog goes! Running, practically flying to catch that car, bus or truck. You are wondering what he would do with it if he caught it. Maybe your thoughts should be "What if it catches my dog?"
Car chasing is not only annoying: it is dangerous for both your dog and the drivers who try to avoid hitting him in the middle of the road. Dogs are highly instinctive pack animals. In the wild, they forage for prey. Anything moving can be that prey. Others may be exhibiting territorial rights and keeping an intruder from his territory. Although many dogs will chase a stick or ball or creature in their yard, they must be taught what is okay to chase, and what isn't.
If you can figure out why your dog is chasing cars, step one will be complete. If he chases the delivery man, you may consider taking the dog out on a leash and letting him meet the delivery man. He can then be made to realize said delivery man is not a threat to his territory and that it is okay to let him in your driveway. This can be done easily once you determine the cause of the chase.
Herding dogs are bred to round things up. It's possible that your dog is trying to herd these vehicles into his desired location. This is more common among Shelties or Collies. It would benefit both of you if you could train your dog for the herding trials or perhaps agility. Something as simple as throwing a ball or Frisbee may satisfy his needs. This particular type of dog is job oriented and needs a task to please those instincts.
That covers the herding dogs. What about those predatory instincts? Dogs in your home don't have to hunt for food. Often this can be corrected by the simple use of a leash or perhaps providing a distraction such as a loud noise. Clapping your hands or putting pennies in an empty soft drink can (tape it shut) and shaking it will usually get their attention. Rewarding the correction with an occasional treat or praise will encourage your dog to behave in a more appropriate manner when outdoors.
The most practical way to stop your dog from chasing vehicles is to keep it in the house or within a fenced enclosure which will keep it from running free. Some dogs are jumpers, some are climbers and some are diggers. Jumpers and climbers can be stopped if they do, in fact, have no issue jumping over your fence. Adding a slanted section to the top of the fence for it's entire length will help tremendously. If your dog is a digger, place chicken wire approximately one foot below ground around the perimeter of their area.
These are simple but very necessary steps to keep your dog safe. It is a behavior that the veterinarian can't cure and one that you can excise yourself without the expense of a dog behaviorist. Take your time, be patient and give praise or rewards. Treats or a favorite toy may be enough to prevent your dog from being caught by that car, truck or bus and sacrificing his life for the chase.