The phrases "driving while intoxicated" and "driving under the influence" most often bring images of being behind the wheel of a car. What Colorado residents may not be aware of is that you can also get a DUI riding a bicycle. The Colorado DUI laws make it illegal to bicycle drunk, but admittedly, this part of the laws is rarely enforced and the penalties are different.
Anyone actually charged with a DUI while riding a bicycle is not in danger of losing their license for refusing to submit to a blood alcohol test. However, an officer's trained observations may be enough to warrant a charge of DUI. Authorities do admit that it's more difficult to tell if someone is drunk on a bicycle, and vehicles are their main priority.
Officers in one small Colorado town admit that they can count on one hand the amount of bicycle DUI's they have seen in their careers. One bicyclist was charged because he ran into the officer's patrol car with his bike--the officer wasn't able to ignore that. Otherwise, since officers need a reason to pull someone over, they are generally not in the habit of chasing down bicyclists, mainly due to the potential danger to the rider.
Granted, a drunk bicyclist is nowhere near as big a threat to public safety as a drunk motorist. The biggest danger to a drunk bicyclist is from themselves since both judgment and reaction times are diminished, and there is a real danger of riding out into traffic or riding into some other obstacle. Since it is technically against Colorado's DUI laws, the best course of action is still to find a ride home with someone who hasn't been drinking.
Source: Coloradoan.com, "Bicycle DUIs rare as drunk riders pedal home from Old Town Fort Collins," Robert Allen, July 29, 2012