A busy junction in Preston was operating without the aid of traffic lights.
Garstang Road where it meets Blackpool Road had no traffic lights due to a power failure.
The A6 was gridlocked for much of Wednesday (11 October) with the lights going out around 6am.
It combined with a major crash on the M6 at Junction 32 northbound to send Preston into gridlock.
Drivers reported being stuck for more than an hour on Garstang Road.
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Electricity North West are investigating the incident and working to restore power to the lights.
A spokesman for the county council said: “The traffic lights on Blackpool Road and Garstang Road haven’t been working this morning because of a mains power failure which has affected the area. Electricity North West are currently looking into this issue.
“This will have contributed to localised congestion, but the extra motorway traffic was the major reason for the delays experienced across the city and the wider area.”
The lights were switched back on at lunchtime on Thursday (12 October).