The ex-Oasis frontman played two nights at Knebworth.
Hertfordshire Police fined several drivers on Friday for using the A1(M) as a drop-off point, and the road was closed for two hours on Saturday as people spilled onto the carriageway.
The event’s organisation, according to attendees, was “a shambles.” Festival Republic has been contacted for comment.
Following the show on Friday, Hertfordshire Police issued a tweet informing fans that fixed penalty notices had been issued to those who used the motorway to drop off and pick up attendees.
This would “not be tolerated,” it said, urging drivers to use designated on-site areas.
The road was closed in both directions due to a “police incident” and “pedestrians wandering on to the A1(M)” on Saturday, according to National Highways East.