Availability isn't the question. I'm assuming the survey question is "do you drive to work or take public transportation."

I have the ability to take a train to work, but it would take me an extra 30 minutes or so each way because I live only a minute walk from the train station, but my job is about a mile away. Also, the train costs me more than driving. I've done it, and would rather do it, but it doesn't work well enough.