While it's true that there's eventually an effective limit to how many highway lanes we can add, we're nowhere close to it yet in the Denver area.  And it's pure lunacy to suggest adding more capacity HURTS traffic, as we hear from some on the left.  

What hurts traffic is continued rapid population growth.

That doesn't mean that transit NEVER makes sense to add to the mix though, in the right situation.  Express bus service into downtown Denver, for example, is/was a very effective service.