The M25 clockwise has been left gridlocked following a collision at junction 18, for Chorleywood in Hertfordshire.
Three lanes were closed because of debris on the carriageway, leading to heavy traffic and severe delays of at least 90 minutes back to junction 16 for the M40.
Lanes two, three and four were shut in between the slip road while the two vehicles were recovered.
Emergency services and Highways England traffic officers were at the scene following the incident near Rickmansworth, which happened shortly after 9am.
We'll keep you posted on how the situation is progressing with live updates below.
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Collision occurred after 'driver became unwell at the wheel'
The possible reason behind this morning’s crash has been revealed by police.
A spokesman for Hertfordshire Constabulary said: “
“Police were called at 9.01am today to reports of a collision on the M25 at junction 18 clockwise.
“One vehicle was involved (a white truck).
“The ambulance service attended and it is believed that the driver became unwell at the wheel.”
All lanes are now open and delays are starting to ease
Highways England confirmed the scene of the crash is clear.
A spokesman said:
“All lanes are now open on the M25 clockwise within J18 at Rickmansworth following an earlier collision and spillage.
“Delays remain in the area but are already starting to ease.”
Lanes remain closed
At present, two lanes remain closed and traffic is still heavy between Junction 16 and 18.
Traffic has eased up elsewhere on the M25...
Traffic is still bumper to bumper near the M25 Junction 18
Delays are finally dropping, three hours after the collision
Pictures reveal the damage to vehicle involved
M25 clockwise now has two lanes open
There are still severe delays - with two lanes remaining closed at Junction 18 A404 (Chorleywood).
Lanes three and four (of four) remain closed in between the slip road while the two vehicles are recovered. Lane two reopened around 11.25am.
This is the grim picture facing motorists this morning
M25 delays have hit the TWO hour mark
Highways England are asking motorists to find alternative routes
Highways England says there are severe delays travelling clockwise on the M25 in Hertfordshire due to an incident within J18 (Amersham / Watford (W)).
A spokesman said:
“An incident involving a single vehicle has blocked 3 lanes (of 4) causing delays between J15 and J18.
“Emergency services are at scene.
“Road users are advised to consider alternative routes and allow additional time for their journeys.”
The vehicle believed to be involved in the collision
Beds, Cambs & Herts Roads Policing Unit shared a picture of the box van involved in this morning’s crash.
Police posted on Twitter:
“Apologies for delays on M25 junction 17 to 18.
“Three lanes are shut due to a road traffic collision and diesel spillage.”