It all depends on where in Boulder you are living and where in Broomfield you are working. The quickest and easiest bus is Route B from Denver to Boulder. That will stop at the Broomfield Park n Ride which is somewhat south and remote from the rest of Broomfield. You would then have to transfer to another bus. But keep in mind all the local buses have bike racks--for a maximum of two bikes in the front. The Regional Bus, Route B, stores the bikes in the undercarriage luggage so it probably can take more bikes. I am saying all this because many people from Boulder bring their bikes to downtown Denver. So, you can easily start your ride on a bus, take your bike and finish your ride to the destination on the bike.
You will have to take a look at the routes at the RTD website
The Regional Transportation District Home Page
There is also information on the bikes. You can get free bike storage lockers at many of the Park n' Rides. It is just necessary to understand how to load and unload your bike on the bus racks for the local buses. However, for the trains, you must have a permit. It is easily to get and free. All you have to do is read and understand the manual, online, and print out your pass.
Another good option is the Broomfield Call and Ride
http://www.rtd-denver.com/SpecialRid...nR_US36_WW.pdf
It is easy to get from Anywhere in Boulder to where a Bus goes to Broomfield. Your problem is getting to your job in Broomfield and back With this Call n' Ride bus, all you have to do is get to the Park n' Ride and a circular bus will pick you up and take you to your job site, or you can be picked up/dropped off in any area where the bus serves. You can then arrange for a daily pickup that will take you back to the Park n' Ride or to any location on the route. They also have bike racks.
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