I don't know what people expect the Island has a limited road system, many very narrow lanes and can only take so much traffic. When the roads are full that's it, gridlock. In this instance everyone tried to pack on to a mere 5 miles of narrow road.

I saw one chap comment that because it was raining everyone was going to travel by car instead of by foot and bus. this means more traffic was on the road than had been anticipated and planned for.

The last pop festival in 1970/1 had 250,000 visitors and the shops ran out of the food needed to feed them so we ended up running soup kitchens to keep them going until the ferries could ship them out and these had mainly come in on foot.If they had all had vehicles then most would have still been in Lymington waiting for a ferry by the time the festival ended.

Festivals like this on the Island are a nice idea but a nightmare to run properly due to the underlying infrastructure being severly limited. The physical size of the place doesn't help either.
Having lived the first part of my life limited by those Bl*&%£ ferries I am so pleased that I live on the Mainland now.