The collision happened on Lambeth Palace Road, near Westminster Bridge, at around 6.30pm on October 2.
The man was taken to hospital with serious injuries but later died.
The Independent Office for Police Conduct (IOPC) was notified by the Met Police and sent investigators to the scene.
An investigation into the circumstances surrounding the incident has been launched.
The IOPC said it has spoken to the man’s family and will keep them updated.
IOPC director Emily Barry said: “Our thoughts are with the man’s family, friends, and all those affected by his death.
“It’s important we establish all the circumstances surrounding this incident and we are in the very early stages.
“The collision happened on a busy road in London in the early evening when people are likely to have been travelling.
“We would urge anyone who may have witnessed the incident or the moments leading up to it to come forward and report what they saw.”
Witnesses are asked to contact IOPC investigators by calling 0300 303 5588 or emailing lambethpalaceroadrti@policeconduct.gov.uk.