In Driver 1, there was a test at the very start of the game where you had to complete a driving challenge in a multi-storey car park before being able to play properly. It was pretty hard.
In Driver: San Francisco, the garage is an unlockable level (practically an easter egg). Follow the instructions below to get it:
First, you need to complete Smash Activity I. This unlocks you the DeLorean (yes, from Back to the Future). You may be able to see where this is going.
Go to a garage and purchase the DeLorean. Take it out onto the road and reach a speed of 88mph. A message will then pop-up telling you that you have unlocked the 'Blast from Past' challenge - the Garage level. Enjoy!