Ok, this achievement is more about luck than skill. That being said, here are a few pointers that I found helpful. Make sure not to just go in a straight line. Instead, try to turn often while driving at high speeds. The vans are very fast and will stay with you unless you shake them off around a corner, they crash very easy. Also, try to avoid the main roads like highways and such. Road blocks will be waiting and if you get caught it can end very quickly, especialy on the later levels. If you find yourself continuously failing a level, keep retrying because an easier level will eventually appear. This is probally the most frustrating achievement in the game besides Drug Trafficing but with plenty of patience it will be done and over with!