Worried residents are demanding action is taken to move on more than 30 traveller caravans that have descended on Waterwells Park and Ride.
Users of the service alerted the county council and police to the arrival of the vehicles on Tuesday.
As many as 40 vehicles including 4x4s and trucks have been reported at the site this week.
Bus user Peter Hill said: “I used the Park and Ride service from Waterwells on Wednesday and was concerned to see travellers have taken over half of the parking site.
“I do not know how long they have been there but already there is rubbish dumped on the site. I would like to know how long they have been there, how did they get in and what, if anything, the authorities are doing to remove them.
“As a local rate payer, I will be sharing the cost of the clean up operations and their presence is hardly a good introduction to visitors to our city, many of whom use the Park and Ride service.”
Graham Smith, from Quedgeley Parish Council, said: “I was told the travellers had turned up on Tuesday and went down to see how many vehicles were there. There were at least 30 caravans, maybe 40, and it isn’t the first time they have been there either.
“The Park and Ride didn’t seem to be that disrupted by the amount of space that was being taken up, but there was a lot of rubbish being left behind. It is not right, and illegal. They shouldn’t be there. It is becoming a common stop off for them.”
Mr Smith said he was unaware of whose responsibility it was to move the vehicles on .
Quedgeley is becoming a regular stop off for travellers. In the past 18 months, they have set up temporary camps opposite the Gloucestershire police headquarters, off Davy Way and also at nearby Marconi Way, leaving behind litter and a large scorch mark on the ground from a fire.
Police said they were made aware of the arrival of the travellers on Wednesday and are monitoring the situation.
A spokesman for Gloucestershire Constabulary said “Our officers are aware that people have moved onto the site and we will be making further inquiries to find out what their plans are.
"In these situations those who have camped on the land are made aware of the standards that are expected of them while they are in situ and the landowners are consulted so that they can pursue an eviction notice if necessary."
Gloucestershire County Council said it was aware that a number of travellers have parked at the site and is working with police to find a solution as quickly as possible. The park and ride is operating as usual.