My commute by car or bike is exactly the same distance, 18 miles straight along the A40 between Ross on Wye and Gloucester. It takes me around 35 minutes in the car, or (including changing time) and hour and a half on the bike. I enjoy the bike ride, but I can't deny that sometimes if I'm busy at home it's a lot easier to think "sod it, I'll drive to work today". It's much easier to cycle if it's quicker on a bike, as it was when I commuted 8 urban miles to work a few years ago.