Peak-time rail fares have been scrapped on ScotRail services from Monday as part of a six-month pilot scheme.
The cost of a rush hour ticket between Glasgow and Edinburgh has almost halved in an initiative aimed at boosting rail travel.
ScotRail has warned customers that trains may be busier than usual during the Scottish government-funded pilot.
Additional carriages have been added to some services, and the operator said it would be monitoring the situation.
The savings will only apply to routes where peak-time pricing existed previously.
Some of the cheapest tickets available – known as “super off-peak” – will also be withdrawn for the duration of the trial, so at less busy times of the day fares could increase.
The nationalised operator said this would affect only a small proportion of journeys, and removing them would make the system simpler.