Some 30 people availed of the first early-morning rail service from Killarney to Dublin, which was inaugurated yesterday.
The 6.30am service from Kerry will also bring students, workers and tourists to Cork before 8am by train for the first time ever, an Iarnród Éireann spokesman said.
A number of additional services, some serving all stops on the route and including return services to Killarney from Cork and Dublin, also began yesterday following major track upgrading.
The new passing loop line at Millstreet station will allow for extra special trains for major events such as Munster finals or All-Ireland finals, it was also announced yesterday.
Andrew Roche, business development manager with Iarnród Éireann, said the early-morning Kerry-Dublin service was just a little over three hours.
The new services to Cork and Dublin were good for the daily commuter and for those with hospital appointments, Mr Roche said.
The overall service to Killarney was already vital to tourists, and students from Kerry could now commute daily to UCC and the CIT in Cork.
Iarnród Éireann was finalising plans with Bus Éireann for regular feeder service buses from Kent station to the city centre, UCC, Cork University Hospital and CIT, he added.
More than 630,000 journeys were made on the Dublin-Tralee route last year, and this was expected to increase substantially now there were six trains from Killarney to Dublin each way weekdays, Killarney station manager Michael Leahy said.