He photographed into the top deck of the bus from a raised platform, between 5.30pm and 7.30pm.
He used a long lens and very slow shutter speeds.
The resulting effect is almost painterly in quality.
Shot largely without the commuters' knowledge, often capturing intimate moments despite being in a public space, the images have a voyeuristic quality.
Turpin came to refer to the commute as a "period of anonymous 'no mans land' between work and home, a transition from the person known by their colleagues to the person known by their families and friends."
In his statement in the book Turpin comments, "I have sometimes found myself sitting on the bus staring back through the window at the spot in the dark where I usually stand with my camera."
Turpin is an acclaimed street, design and advertising photographer.