Was thinking about this upon arrival at work this morning. The commute to this job involves one leg taking VTA Light Rail several miles. I could have waited for the next bus to take me to the light rail station but instead I rode my bicycle. Comparing between the two, taking the bicycle shaved 15 minutes off the arrival time.
That is - taking the bus I could have completely avoided using my own vehicle. But it would have meant waiting 20 minutes or more for the next bus and taking a later train from the light rail station.
By riding the bicycle I didn't have to wait for the next bus, and instead went directly to the light rail station, and was able to take an earlier train. It did mean part of the commute on my own vehicle.