Up to two minutes could be added to TransPennine Express services so its trains no longer need to use polluting diesel engines over more than half of the route.
Since being introduced two years ago, the Nova 1 trains have been forced to operate under diesel power between Longniddry in East Lothian and Chathill in Northumberland – a 70-mile section of the 120-mile line between Edinburgh and Newcastle.
TransPennine is now investigating whether software adjustments can be made to its Nova 1 trains so that they would draw less electric power from the overhead wires, permitting them to be switched from diesel.
The operator said power supplies may not be upgraded to enable the trains to run at full electric power for another two years.
It said the upgrade of electricity sub-stations included ensuring any impact on an archaeological dig at Marshall Meadows, north of Berwick, was minimised.
The problem has arisen because the necessary upgrades by Network Rail have not been taken into account when train operators announced new train fleets and extra services.
Friends of the Earth Scotland has said the situation is “farcical” when “electricity is flowing through cables just a few feet above the trains”, “needlessly adding to climate change”.
However, the restriction is not thought to affect LNER, ScotRail and Lumo, which also use the line.
TransPennine managing director Matthew Golton said: “We are looking at how you can make a software adjustment to the train so that it can lower the power draw but still operate from an electrical perspective.
"You may lose a couple of minutes over a long journey through running effectively an 80 per cent [electrical] load factor, but you then have got the advantage of using the overhead wires.
"More of the journey between Newcastle and Edinburgh is going to be made electrically.
"Network Rail do have a plan to overcome the issue but we’ve decided it’s worth us proactively looking at seeing if we can skin it another way.”
A TransPennine spokesperson added: “We have worked with Hitachi and other affected train operating companies and identified a solution to the power load factor requirement.
"We expect to make decisions on the nature of the benefits that it offers us and the funding for the work during the next few months.
"We would anticipate being able to deploy within 2023 if it was decided to proceed.
"Authority for electric operation is expected in a range of spring 2023 to spring 2024.”
A Network Rail spokesperson said: “We are investing £1.2 billion on the east coast main line, including delivering significant enhancements to increase power supply to allow more electric services to run on this key route.
“While these upgrades are being delivered, a limited number of bi-mode services will need to operate in diesel mode on a section of the route.
"We are continuing to examine options to increase the number of trains using overhead line power until the upgrade of our infrastructure is complete.”