Motorists driving on the M1 motorway in a southerly direction between junction 11 and junction 10 should expect delays of about 45 minutes and congestion of six miles.
The accident, which is believed to have occurred around 2:45 p.m. on Tuesday, caused the overlap of three lanes on the M1.
Lanes 1, 2 and 3 are blocked near Lutan, causing traffic to move much slower than usual.
National highways reported congestion of five miles and delays of up to 50 minutes.
Details and causes of the collision have not yet been identified.
Police are on the scene to find out the circumstances of the incident.
For the first time the accident was reported on social networks National Highways.
On Twitter, they said: “Lanes 1, 2 and 3 are closed on # M1 in the southern traffic between J11 and J10 nearby (#Luton) due to the collision. National road traffic officers are on the route.”
How many cars were involved in the collision and whether there were any serious injuries is yet to be reported.
Lane 3 was reopened around 3:30 p.m., but lanes 1 and 2 remain closed.
Delays of 45 minutes remain higher than normal travel times, and congestion of about six miles is formed on the approach to the incident.