A deer running loose and a crash on the M4 were among reasons cited by Glastonbury Festival organisers for the roads misery that blighted the start of the event.

A deer on the site meant the gates opened half an hour later than planned, leading to a build-up of traffic on the A39 at Glastonbury, Street, Walton and out towards the M5.

Accidents on the M4 and A39 during the day further compounded the problem, causing chaos on major roads and problems in residential areas as festival fans attempted to avoid the gridlock.

Eye witnesses in Glastonbury and Street said many festival-goers caught in traffic staged impromptu parties at the roadside.

But residents also complained of gridlock, noise and people being forced to urinate at the side of the roads and up against their homes.

By Thursday morning, 90,396 people had arrived on site – up by almost 21,000 on the year before, adding increased pressure on the roads.

And in the early hours of Monday morning, as fans left the site, they faced delays of up to five hours.

Many motorists were angry that aggressive drivers were allowed to push in and jump the queue to get out.

Several cars stuck after an early morning downpour caused further problems, sparking some angry exchanges and blasting of horns.

Calmer drivers turned off their engines, set up deck chairs and played music from the festival headliners on their car stereos.

Crispin Aubrey, a spokesman for Glastonbury Festival, said he understood the frustration of local people who had been caught up in the tailbacks, but said they had done all they could to keep traffic moving.

"No matter what steps we take, the roads in Somerset are narrow and not really designed for hundreds of thousands of cars turning up at once.

"When people arrive on site, we have to get them parked safely and make sure they can get their cars out after the festival is over," he said.

He said traffic management was organised in conjunction with the police and that the festival had increased the amount of car parking available.

"So many more people arrived at the festival early – they were determined to get their money's worth out of the festival, to get the best of the weather and to spend their time with friends.

"For many people, the festival started while they were in the queue of traffic – there were people staging mini parties at the side of the road when the traffic had stopped entirely."

He said the festival had tried to encourage people to car share, or travel by coach or public transport.

"We do everything we can to try and keep the traffic moving but, sadly, when the festival is on, local people will need to put up with some inconvenience, be patient, and use their knowledge of the back roads to get where they want to go."