it's probably even less, maybe even negligible because of traffic lights at either end: you can't calculate a single journey because you're never going to hit the same light exactly the same every time. I have four lights between my house and the freeway, and 7 between the freeway and one of the sites for my job. Each one adds between 0-60 seconds randomly for an average of 6 minutes sitting and waiting per day. I would have to have a commute of like 120 miles of uninterrupted freeway driving for that to matter.