Rush-hour commuters were brought to a standstill on Monday as a man was airlifted to hospital following a multi-vehicle collision on the M25.
Three lanes of the clockwise carriageway were closed as police warned travellers of a "substantial" fuel leak after two articulated lorries and a van collided between junctions 8 and 9, near Reigate and Leatherhead, in Surrey.
The driver of one of the lorries was taken to St George's Hospital in Tooting, south London, in a "serious condition". The occupants of the other vehicles suffered minor injuries, Surrey Police said.
Drivers heading for work and family days out endured delays of up to six hours after emergency services crews headed to the scene, shortly after 8am.
Sarah Brooks, 41, said she and her husband and two young children had been forced to cancel a planned trip to Legoland, near Windsor, in Berkshire, after hitting queues about four hours earlier.
"We're probably not going to get back during the Easter holidays because this is my husband's only week off and I work at a riding school so I will be quite busy," she said.
"We will go, but they might only give us a week to revalidate so we're not quite sure of the terms yet."
Posts on social media showed some of those caught in the traffic had abandoned their vehicles for spontaneous football kickabouts and guitar practices, as others were spotted relieving themselves across the hard shoulder.
Brooke Collyer, 16, said her trip to Thorpe Park resort to celebrate her 15-year-old brother's birthday was in danger of being limited to just an hour after her family were stuck for more than three hours after setting out from their home in Heathfield, East Sussex.
Motorway authorities later reopened one lane on the clockwise carriageway at around 1pm, but other lanes remained closed as road workers attempted to clear the fuel spillage.