Police temporarily closed part of the M1 in Hertfordshire last night after two cars crashed.
Emergency services attended the scene at junction 5 northbound at about 8pm.
The M1 reopened fully at 10pm after the accident was cleared.
National Highways said the closure affected traffic between Watford at junction 5 and Bricket Wood at junction 6.
At the time, Herts Police tweeted: "We are currently dealing with a collision on the M1 at junction 5 northbound. All emergency services are on the scene and the carriageway is currently closed.
"Please avoid the area where possible."
Delays of 20 minutes were reported once the road was fully reopened with three miles of congestion on the approach.
It's unknown if anyone was injured in the crash.
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