More than 500 ScotRail passengers have been caught dodging more than £17,500 worth of fares.
In one case, a businessman who had taken 53 journeys over the course of a few months had to pay £2300 in missed fares and administration fees.
ScotRail said it recognised it was relatively easy for passengers to get on trains without paying, as only 17 of the 350 stations it operates are equipped with ticket barriers.
However, the company warned passengers that CCTV cameras can prove where their journey began and ScotRail can then work out how much they owe.
It said 533 fare dodgers had been forced to hand over £17,600 since August.
Phil Campbell, ScotRail’s head of customer operations, said: “A minority of our customers are taking advantage of the fact that due to coronavirus restrictions we are unable to put ticket inspectors on our trains or at most of our stations.
“While most of the population is sticking to the rules, these passengers are using the cover of Covid to avoid paying for their ticket.
“Revenue on the railway is down by around 90% due to the pandemic, so it’s vitally important that in order to give the best value to the taxpayer, we collect as many fares as possible.
“We have caught a number of repeat offenders and the message to anyone thinking of dodging their fare is simple. We are watching and we will catch you.”
ScotRail said all the passengers who have been caught so far have paid up since the alternative is prosecution which, if successful, would leave them with a criminal record.
The company said that there has also been an increase in the number of assaults, verbal or physical, on staff who ask customers to pay for their ticket.
It has held joint operations with British Transport Police to crack down on anti-social behaviour, focussing on specific areas across the network to provide additional support for ScotRail staff.
Grant Whyte, a revenue delivery supervisor at Glasgow Central, who has been with ScotRail for 30 years, said: “It’s unbelievable that some people are not only trying to get away with travelling for free, but are also shouting or getting physical with staff who ask them to pay for their ticket.
“Some staff have been spat on or pushed out of the way by passengers who don’t think it’s right that they should be paying for their journey because they’ve been getting away with it for so long.”