Trains are now operating on the Cumbernauld to Glasgow line, the first completed phase of the Edinburgh to Glasgow Improvement programme.
Keith Brown, Transport Minister, took one of the first services on the newly electrified line with passengers into the city.
Transport bosses said the improvements, costing £80million, will see more reliable services and double the number of travellers carried on the line.
Mr Brown said: "The launch of these electric services is a huge milestone for the EGIP project and the Cumbernauld electrification has been delivered on time, on budget and well ahead of this summer's Commonwealth Games, as promised.
"All of the partners involved have worked well to get to this stage and we are now getting to see these exciting plans beginning to come to life."
The 30-mile stretch of track has taken almost one year to electrify, but now means more trains between Glasgow and the new town, and earlier and later services between Cumbernauld and Motherwell.
Services will increase from 36 to 59 to carry 11,500 passengers, up from the 5500 before electrification.
Rail bosses said the improvements will allow numbers to grow on the route as passengers see improved reliability and with trains stopping at more stations in the city.
Steve Montgomery, managing director of First ScotRail, said: "More than 800,000 journeys are made on this route each year and I have no doubt this will continue to grow now that we are introducing more modern, regular and reliable trains."
Network Rail, which manages the track, said the target for the overall project, was to complete quickly and at the lowest cost to the public.
David Dickson, Network Rail route managing director for Scotland, said: "We are pleased to have been able to deliver another significant part of the strategically-vital Edinburgh-Glasgow Improvement Programme on time, on budget and in readiness for the Commonwealth Games.
"We are making good progress elsewhere in developing plans for the electrification of the main Edinburgh-Glasgow line."