"Gridlock" is the third episode of the third series of the British science fiction television series Doctor Who, first broadcast on BBC One on 14 April 2007. It was written by Russell T Davies and directed by Richard Clark.

In the episode, alien time traveller the Doctor (David Tennant) takes his new companion Martha Jones (Freema Agyeman) to New New York in the far future, where they discover the remainder of humanity on the planet live in perpetual gridlock within the Motorway, an underground highway system. When Martha is kidnapped, the Doctor races to find her before she enters the dangerous "fast lane".

"Gridlock" completes a loose trilogy that began with "The End of the World" (2005) and "New Earth" (2006), and contains hints at the series' story arc. The story is designed to show how the Doctor can bring hope into a world. Production of "Gridlock" took place in September and October 2006. Much of the episode was filmed in-studio and used a large amount of computer-generated imagery, so it appeared to be set in a "CGI world". Some location filming was done in Cardiff, most notably at the Temple of Peace. "Gridlock" was viewed by 8.41 million viewers in the UK and received generally positive reviews from critics.

The Doctor takes Martha in the TARDIS to the year five billion and fifty three and the city of New New York on the planet New Earth. They end up in an alleyway where street traders are selling mood patches to help people deal with their emotions. While the Doctor talks to a vendor, Martha is kidnapped at gun point by a young couple named Milo and Cheen. Once in their vehicle, they explain that Cheen is pregnant and that they needed three adult passengers with them to use the fast lane. They promise they will drop Martha off when they reach their destination ten miles away, estimated to take six years. Cheen also mentions rumours about something living down in the fast lane, saying that cars that go down there vanish and are never seen again.

...
Wikipedia