RAIL passengers must have access to "high quality and reliable" wifi, the new ScotRail operator has said as it revealed plans to improve network coverage.

Abellio has already committed to rolling out free wifi on all ScotRail trains by the end of 2018, but the Dutch rail firm now says it wants to upgrade the service so that it is less likely to cut out.

The Scottish Government has invested more than £4.4 million in wifi across the ScotRail network, but passengers travelling on key commuter routes such as Glasgow-Edinburgh regularly complain about losing signal.

John Seglias, Abellio's Group Chief Information Officer, said good wifi was "increasingly important" to rail passengers.

He added: “We don’t just want to say to our customers that our trains are wifi connected. That’s not enough. We want to ensure that they receive a high quality and reliable service when they connect.

"As a result I’m pleased that we are currently tendering across a range of technology suppliers for the best solution. We are also in discussion with the major mobile operators on ways to improve existing coverage and reliability as that has to be part of the overall solution.

"Where wifi is available now, we are also looking at immediate ways in which it can be improved.”

Richard Muir, deputy chief executive of Glasgow Chamber of Commerce, said it was a welcome ambition.

He said: "For many business people a train carriage can act as substitute office space while they travel between cities so having the best quality communications infrastructure is essential for sustaining productivity while on the move."

ScotRail currently relies on picking up a 3G signal from ordinary commercial phone masts outwith the railway which is then "forwarded" to passengers via the on-board wifi system. As a result, coverage can be patchy - particularly in rural areas, or when passing through tunnels and by embankments.

There have been major advances in the technology in recent years, however, which may offer a blueprint for ScotRail.

In 2007, the Heathrow Express claimed a world-first when it deployed 4G wireless broadband on trains that travel underground through nearly four miles of tunnels.

Instead of phone masts, the trains were fitted with black box antennae that "listen" for signals coming from wireless base stations installed along the tracks, allowing passengers to receive a continuous and strong network connection.

The system was developed by T-Mobile and Newcastle-based Nomad Digital, the same firm hired by Abellio's parent company, Nederlandse Spoorwegen (NS), to install wireless internet across its entire intercity fleet in Holland. NS is now working on plans to roll out superfast 4G across the Dutch network.

The type of "train-to-ground" connection used by the Heathrow Express is also set to be extended throughout the London underground by 2020.

Meanwhile, the Department for Transport announced in February that £50 million worth of punctuality fines levied against Network Rail would be funnelled back into the railway to fund free wifi across four franchises in England and Wales: TSGN, Southeastern, Chiltern and Arriva Trains Wales.

Commuters on these routes have been promised wifi up to 10 times faster than the current average within four years, and will log on via equipment installed along the tracks.

A UK-wide rollout of line-side wifi has stalled, however, with Network Rail, DfT, train operating companies and other industry stakeholders unable to agree on a private sector supplier during a recruitment drive last year.

A spokesman for Network Rail said: "Despite a range of positive bids, we have not been able to find a solution which satisfies the commercial requirements of all parties while delivering the desired level of service for passengers on the rail network.

“Network Rail and train operators remain committed to working with the rail and telecoms industries to find ways to improve voice coverage and access to high-speed broadband as swiftly as possible.”