Driving
It is not necessary to own a car in Boulder, but it is not difficult to have one, either. The downtown area has multiple parking garages, and they are often free after hours or on weekends. Most apartment complexes and neighborhoods have ample parking.
Parking on or around campus, however, is a whole other story. While it is good to have a car for other reasons, it is not a good idea to plan on driving to school. Permit parking is expensive and limited, and parking in the "Hill" neighborhood adjacent to campus is usually pretty full. For commuting, we recommend either biking, walking, or taking advantage of Boulder's excellent bus system.
Questions regarding car registration and emissions standards for cars in Boulder can be found at the County Clerk and Recorder Site.
Biking
Boulder is perhaps the most bicycle friendly city in the U.S. Commuting by bike is easier than commuting by car, and can be easily coupled with the superb bus system. Traffic in Boulder is surprisingly bad, and the bike paths not only allow you to avoid the stop lights and traffic, but often allow you to take a more direct route to your intended destination. There is a huge network of bike paths that link all areas of Boulder that I like to call the underground railroad. In the winter, the paths are always cleared of snow before the roads are, and the paths keep you clear of unruly motorists. Unlike larger cities, bikes are fairly safe locked up on the streets of Boulder, so you dont have to worry about returning to find your bike stripped to the frame. For more information take a look at the "Biker's Map of Boulder".
Taking the Bus
Student fees paid to the university each semester include a bus pass which is good for unlimited rides on all local and regional buses in the Boulder-Denver area, including the bus to the Denver International Airport. A complete list of these buses, their schedules, and maps are located at www.rtd-denver.com. Information more localized to Boulder can be found at http://www.ci.boulder.co.us/pwplan/.
Since we get an unlimited bus pass each semester, we've found that it's better to live on a direct bus route than to necessarily live close to campus. Most grad students would agree the bus system is quite well organized and efficient. You will be surprised how often the weather will permit you to walk or bicycle to campus, but it also isnt a bad idea to know how you are going to get to campus when the weather is lousy.