Lying on your stomach for days on end in a puddle of your own piss, doing math just to make sure you can even hit the speeding vehicle isn't really as easy as it sounds, just throwing it out there.
You wouldn't need to be camouflaged - You could shoot from a comfortable hide that has a speed camera relaying which 'target' you need to take out. Your position would be directly in front, so no need to take into account a moving target. :~)