It definitely depends. The time of my commute itself is about the same, whether I bike or drive. However, there is about a 10 minute difference from additional activities that are not needed when driving. When I bike (~80% of the time), I need to account extra time for strapping my bag to my bike, attaching/removing easily stolen accessories, donning/removing reflective vest, and changing from biking clothes to business casual after arriving.

Thankfully, my commute is short and summers aren't too hot, so I don't yet need to add an additional 10-15 minutes for showering after arriving.

This is the case for me. I live about 6.5 miles from my office. Congestion is so bad (I'm in the Seattle area) that it can take upwards of half an hour to get to work -- yes, that's an average speed of 13 miles an hour in a car. Miserable.

However, on the bike I can average nearly 15 miles an hour, so I actually save time! In all fairness that time is more than eaten up by the additional steps (don bike gear, load bike, etc.) but it's nearly a wash.