A man is believed to have been talked down after threatening to jump from a bridge at Swakeleys roundabout.
Officers attended the scene of the roundabout, on the A40, during rush hour on Monday evening (June 15).
A Metropolitan Police spokesman said: "Police were called at 5.30pm concerning the welfare of a man at the A40, Park Road, Swakeleys roundabout.
"Roads were reopened at 6.06pm."
Delays were reported on the road, at Ickenham, due to the incident.
If you are affected by the issues raised please call Samaritans on 08457 90 90 90 or visit their website.