POLICE will take a "common sense" approach to enforcing a new alcohol ban on ScotRail trains and will not arrest everyone caught with a drink after 9pm.

British Transport Police are instead aiming to focus on preventing people who are already drunk from getting on services and will respond to incidents where passengers refuse to heed warnings from train staff to stop drinking.

Chief Superintendent Ellie Bird, area commander for British Transport Police (BTP) in Scotland, said she believed the curfew would be widely respected and that passengers would undergo a change in attitude similar to that which accompanied the introduction of a smoking ban six years ago.

Speaking to The Herald ahead of the ban taking effect on July 20, she insisted the move would not require an increase in police resources and would help reduce assaults on train staff and delays to services.

"It's not just a policing solution, it's about educating people to say that's not acceptable. If you look at the smoking ban, the same thing happened. It became unacceptable to do it," Ms Bird said.

She said the police response would be on a "discretionary" basis, based on police resources and the seriousness of the incident. "We're not going to stop a train if someone is drinking alcohol," she added.

"We don't need to increase police resources. It's about being proportionate. The last thing we want to do is to hold all trains while ScotRail wait for the police to arrive."

The ban, which will be implemented on all ScotRail services apart from the overnight Caledonian Sleeper, has been made possible due to a "massive" drop in cable theft and serious crime on the railways, with fewer than five incidents reported across the network, including stations, per day, Ms Bird said.

"Having made some real achievements in reducing serious crime, we've set about focusing on other aspects affecting passengers, staff, businesses and a lot of people in Scotland. That's anti-social behaviour," she said.

"We also know staff assaults increased last year, which causes considerable concern and we know a high percentage of those assaults are alcohol-related.

"We're working with First ScotRail to minimise disruption as we know a number of incidents relating to disruption are caused through predominantly alcohol-related behaviour, whether that's someone who is so drunk they fall off the train and disrupt the departure or rowdy behaviour."

Steve Montgomery, managing director of ScotRail, said the ban was a "reasonable" balance between allowing people to drink alcohol and tackling anti-social behaviour. He said: "We provide a service for people who go out and enjoy their leisure time. It's not about stopping people doing that.

"Staff are very supportive because they're at the front end of it when something does kick off on a train. It's all about educating the public not to drink alcohol after nine."

He insisted passengers had no right to expect to get on a train if they were so drunk they were being carried on by friends. Although such behaviour can be prevented with existing by-laws, these would be applied with more rigour, he said.

"If someone is unfit through alcohol, why should they be allowed onto a train? They wouldn't be allowed on any other form of transport," Mr Montgomery added.

As well as enforcing the Scotland-wide ban on alcohol, BTP will be undertaking targeted action on services where problems have been identified.