Boulder, Colorado is approximately 27 miles northwest of downtown Denver. From Denver take I-25 north to U.S. Highway 36.  Continue west on U.S. 36 until arriving in Boulder.  From the western suburbs of Denver (e.g. Golden), take Colorado highway 93 north into Boulder.  Once you arrive in Boulder, highway 93 is renamed Broadway, which continues north through the city past the University of Colorado and the Pearl Street pedestrian mall.  Highway 93 eventually exits the city's northern edge and conitunes north towards Lyons and Estes Park.  If you are coming to Boulder from the north, take Colorado highway 119 west from I-25, through Longmont,  Colorado highway 119 merges with Foothills Parkway when entering the city.

 Denver International Airport is the closest major airport (with regularly scheduled commercial airline service) to Boulder.  From Denver International Airport, take Peña Boulevard west to I-70 (do not take the toll road that leads to I-70).  Continue west on I-70 until reaching I-270.  Take I-270 west until reaching U.S. highway 36, which as described above, will lead you to Boulder.  Alternatively, especially if you are traveling during rush hour, you can take the Northwest Parkway toll road to Boulder.  From the airport take Peña Boulevard west to E-470.  Go north on E-470 until it merges with the Northwest Parkway.  Continue on the Northwest Parkway until it reaches U.S. highway 36 (near the city of Louisville).  Continue west on U.S. highway 36 until you reach Boulder.

When attempting to travel in and out of Boulder during rush hour, which is from about 6:30 a.m. to 9:00 a.m. Mountain Time and 4:00 p.m. to 6:00 p.m. Mountain Time, drivers should allow plenty of extra driving time. Traffic can be very heavy during those times.

Public transportation in and out of the Boulder area is fairly easy. There are frequent busses available through the Regional Transportation District (RTD), which only cost about $12 to and from Boulder and the airport. There are also several types of shuttles and limousines, such as Super Shuttle, that cost about $20 per person for a ride to Denver’s airport. Taking a cab to and from the airport is the most expensive way to travel, but if that is the desired method, it may cost about $90 per trip. There is also a Hertz Local Edition office at 49th and Pearl Street, which offers one- way rentals to DIA as well as local rentals. Very nice if you take a shuttle/bus from Denver and then want to explore the area a bit more. (ie, no other way to get to Estes Park/Rocky Mtn, National Park without a car!). The Hertz Local Edition offers the same service as one would get at an airport location, but with lower prices and they will even come and pick you up at your hotel.  Many visitors will choose to take a shuttle into Boulder and then pick up the rental car to save money.