And at 7.30am TfL revealed all traffic lights were out at the busy stretch of road in Hillingdon due to the collision.
Reports say traffic is queueing at the junction with congestion backing up to the High Street.
Buses are not being allowed to turn right onto Bath Road due to damaged traffic lights with routes 350 and U3 running on a diversion.
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But traffic appears to have eased
There’s no big red blob on the TfL map now
Central crossing closed
TfL say: “The central crossing has been closed for safety reasons”
Ealing incident: All lanes reopened
getwestlondon understands all lanes have reopened on Gunnersbury Avenue in Ealing (see tweet below)
Meanwhile in Ealing...
The incident has had a knock-on effect
'Collision reported on A4'
Here’s how TfL told us of the problem this morning
Traffic lights down
The incident has resulted in traffic lights failing at the junction
Congestion at junction
A4 collision near Heathrow Airport
Traffic is building on the outskirts of Heathrow after a collision on the A4 Bath Road at Hatch Lane this morning