Passengers have criticised a new system set up to help combat fraud on First buses in Bristol.
First said the move was not to make money from customers
When drivers are unable to give a passenger change a "change ticket" is issued which can only be redeemed at two travel shops in the city.
Previously this ticket could be used towards a new fare but this was stopped after some had been copied.
Rachel Hicks, spokeswoman for First, said the move was solely to target fraudsters and not passengers.
"The idea is not to make money out of our honest customers, this is aimed at people defrauding everyone else.
"In the longer term we are looking at other measures to make tickets that are impossible to copy.
She added: "At the moment the only way to combat this is to get passengers into travel shops."
The change tickets are valid for seven days and can be redeemed at the travel shops at either Colston Avenue or the bus station in Marlborough Street.
Some bus passengers said the system sent out the wrong message at a time when people were being encouraged to use public transport rather than cars.
One woman passenger told the BBC: "They say the measure is to combat fraud, but who is going to bother for 20 or 40p?"
Phil Tonks from Bus Users UK said a similar scheme had been in place in the West Midlands since the '70s.
"Most regular passengers have the right money and this makes it very easy to fill a bus with passengers quickly.
"[Not having the right money] is an issue with some new passengers.
"It is an inconvenience which in the longer term needs sorting out."