The Chiswick flyover was a part of the M4 motorway.
On her wedding day, 24 December 2007, Donna Noble got into a taxi which she hoped would take her back to the church, but instead it turned onto the M4 and headed along the Chiswick Flyover. The Tenth Doctor, in his TARDIS, was able to rescue her. (TV: The Runaway Bride).
At some point between 2008 and 2010, a female sentient concrete disguised itself as the Chiswick flyover and telepathically controlled people. (TV: The Nightmare Man) Sarah Jane Smith and her friends defeated and destroyed it, with only part of the sentient concrete remaining. (PROSE: The Nightmare Man)