A small number of passengers travelling on the Phoenix Park tunnel line for the first time this morning were faced with ticketing problems after vending machines at a number of stations failed to offer travellers the option of buying tickets to Grand Canal Dock.

The ticketing issue, which affected passengers travelling from Newbridge, Sallins and Naas, Hazelhatch, Adamstown, Clondalkin/Fonthill and Park West and Cherry Orchard stations, was rectified by 7.30am on Monday, according to an Irish Rail spokeswoman. Tickets to Grand Canal dock were available from ticket offices from 8.30am.

As most people travel using leap cards or rail cards, very few passengers were affected by the ticketing problems, said the spokeswoman. She added that those unable to buy tickets were permitted to travel on the train line without tickets until the problem was rectified.

The Phoenix Park rail tunnel began ferrying passengers this morning between stations north and south of the Liffey for the first time in more than 100 years.

The new services connecting stations between Newbridge and Parkwest with Connolly and on to Grand Canal Dock comes with a price tag of €13.7 million, which was paid by the National Transport Authority.

The tunnel connecting the State’s two busiest train stations runs for 692 metres under the Phoenix Park and up until now was only used to transfer small amounts of freight as wells as engines and out-of-service trains.

Travelling from Connolly, the service starts out on the Sligo-bound track passing Croke Park and Drumcondra Station before reaching Glasnevin Junction where it branches off and heads south through Cabra.

It then goes underground close to the Garda Headquarters in the Phoenix Park and snakes in the direction of the Wellington Monument before going under Conyngham Road and emerging so it can cross the Liffey over a rail bridge and into Heuston Station.

The service should prove attractive to as many as 7,500 people living in a commuter belt stretching from southwest Dublin into Kildare although it may take time for passengers to fully embrace the seven new morning peak trains to Grand Canal Dock and the eight new evening peak trains from Grand Canal Dock, according to Oliver Doyle of the Irish Railway Records Society.

“It might be even three or four years before we know how popular it is going to be although we will have pretty good indication within six months,” he said.

Mr Doyle, who worked with Irish Rail until his retirement, said that when the tunnel was first opened it was “primarily for freight and also used to send an awful lot of mail from the UK to the United States. They figured out it was faster to send the mail by boat to from Liverpool to Dublin and then on by train to Cobh before going to the United States than putting it on boats leaving from Southampton, ” he said.

For a brief period at the beginning of the 20th Century the tunnel was used for regular trains with both Drumcondra and Glasnevin Stations built to cater for commuter traffic. “The service didn’t really work because the track took a very circuitous route around the city and people were looking for more direct access,” he said.

“The most important about this development is that it will finally connect the two halves is of the Irish rail system,” he added pointing out that if the demand were there it would be possible to take a direct train from Cork to Belfast for the first time in more than 60 years.