I had also found a software tool a few weeks ago that allowed a business to plug in a bunch of entering arguments and then calculate the benefit to the company of promoting or incentivizing alternative forms of commuting. Depending on your company's situation, there are many potential and obvious benefits to the bottom line, nevermind the more nebulous notions of contributing to the general welfare of the local and global community.

I can't recall where I saw that tool, though. I'll see if I can dig it up.