I can drive to the Exploratorium in 20 mins. The BART ride is 22 mins, but it includes over 15 mins' walk at each end, meaning the total journey time is 2.5x.

I can drive to the Exploratorium in 20 mins. The BART ride is 22 mins, but it includes over 15 mins' walk at each end, meaning the total journey time is 2.5x. This 2.5x to 3x is typical, in my experience. If I'm on my own, it's faster to cycle than to take public transport.