A short drive, typically in a circle of some sort, on which one or more people smoke marijuana and socialize. This sounds dangerous and may seem like the easiest way to get busted but, depending on the town/city, it can be the safest way to smoke pot.

The origins of this method of smoking marijuana are based on the ignorance and ineffectiveness of the typical small town/city police department. As an example, in my town, the police regularly patrol only about three or four "back roads" beyond the town center where they are content harassing college kids. Logically, the safest place to smoke is any place where the police are scarce, i.e. the back roads. Though the occasional main road will be encountered, the goal is to use as few main roads as possible, usually only for a few seconds, before crossing it to the next back road. The more continuous the back road path you take, the safer it can be considered. Also keep in mind, that at night it is very difficult to see into oncoming traffic's windows, making looping much much safer after dark.

A major concern that many people voice is that they might get lost, especially after they're high. If you think about the layout of your town, you usually know where all the major roads are (routes like 35, 116, 121, etc). Keeping these in mind as "border roads", try wandering around in between them. If you see a road that you don't know, take it and see where it ends up. As long as you are in your own town and can recognize when you've hit a main road, you are all set. If you hit a main road and have no idea where you are, pick a direction. You can't have gone too far, and the chance of picking the right direction is a solid 50/50, even better if you have a compass. Soon enough, you will have learned a good amount of the back roads of your town with minimal effort. From your newly aquired knowledge of the major back roads (if you don't know what I'm talking about, keep exploring, you'll get it), you can then extrapolate where the lesser known back roads may take you without hurting too many brain cells.

Some tips for when on a loop:
1) Pass the smoking device (pipe, joint, etc) counter clockwise so that the driver does not get the device passed to them from behind, as it is quite distracting.
2) If you aren't sure where you are (it happens to the best of us), pick a direction and stick to it. In all likelyhood you are already going the correct direction and forgot. Worst case, you wind up a little out of your way, but have eliminated the hours of endless circles that taking random turns would lead you through.
3) Leave your brights off so that when unexpected traffic comes the other way, you aren't struggling with the steering wheel, smoking device, AND the light controls.
4) Take #3 a step further and learn to steer with your knees. It takes practice, but its worth it.
5) Have someone keep a cigarette handy in case you get pulled over, it'll mask the smell of marijuana almost instantly.
6) If you wish to go on a loop with only select people from a larger group, get their attention subtley. Then raise your hand from the elbow (remember this is supposed to be stealthy), extend your index finger upwards and rotate in a circle. This movement should resemble a very understated "Party Time", or the sarcastic "Woop De Fucking Do" hand gesture. And, of course, don't say anything at all that would indicate where you are going. Exchange head nods and bounce.
7) Don't smoke with the dome light on (for instance when you are changing CDs). Tell whoever has the smoking device to wait until the light is off.
8) Assume any other car on the road is a cop until proven otherwise.
10) There is no such thing as acting too paranoid when on a loop. As the driver, do whatever you feel is neccesary to ensure your saftey from the police. This includes taking random turns to lose cars that might be following you.