Traffic is building on the A40 eastbound near the Hanger Lane tunnel in Perivale due to a broken down lorry.
CCTV footage taken at just after 12.30pm on Thursday (November 8) shows the lorry stuck in the middle of the road, with queues building up behind it.
The lorry is straddled over both lanes of the road, meaning one lane is closed and the exit to the slip road is partially blocked.
Congestion has so far already built up to the Medway underpass.
At 12.40pm, TfL Traffic News tweeted: "On the A40 Western Avenue, there are lane closures heading eastbound before Hanger Lane Tunnel due to a broken down HGV.
"Traffic is slow on approach behind it."
Drivers passing through the area near Hanger Lane Tube station may want to plan an alternative route.
Follow our liveblog below for more updates as this situation progresses.
Traffic lights not working just a short way down the road
Traffic lights at the Greenford Flyover just a short way down the road are not working.
Drivers are advised to approach the roundabout on Greenford Road with care.
The traffic lights have not been working since 9am today (November 8).
Where did the accident take place?
The lorry broke down just before Hanger Lane tunnel outside Hanger Lane Tube station.
Traffic can be seen building up on both sides of the accident, particularly to the east.
What we know so far
A broken-down lorry on the A40 eastbound just before Hanger Lane tunnel has blocked one of two lanes and partially blocked the slip road exit.
Traffic is slow behind the vehicle and congestion has already built up to the Medway Underpass.
