Trains on the Heart of Wales line – from Swansea to Shrewsbury via Ammanford, Llandovery and Llandrindod – had to be doubled in length to cope with the influx of people taking free day trips on the scenic line.

Rail managers expected the offer to be popular for the first weeks, but were surprised when passengers continued to pour onto the trains through the rest of the summer, despite the poor weather.

Another pilot brought more passengers to the Conwy Valley line, including some pensioners who were keen to try the train although they refuse to use buses in preference to their cars.

The pilots’ success could leave the Welsh Assembly Government with some hard choices. Extending the concept to other rural areas will require money for extra trains if the additional passengers exceed the spare seats on existing trains.

The two pilots alone are costing the WAG about £150,000, to compensate Arriva Trains Wales for fares that would otherwise have been paid and to fund the longer train on the Heart of Wales line.

The pilots were launched on May 20 as an extension of free bus travel, offered to pensioners and disabled people since 2002. Residents of counties directly served by the two railways were eligible. Free Heart of Wales travel was offered to inhabitants of Swansea, Carmarthenshire and Powys but not Neath Port Talbot, which almost touches the route at Ammanford.

Mike Bagshaw, ATW’s commercial manager, said, “We thought there would be a burst of interest and it would die down as the novelty factor wore off, but it’s continuing beyond our expectations.”

Passenger numbers on the main Heart of Wales services, excluding the early morning ones, were double last year’s figures.

A WAG spokesman said, “The Assembly Government is contributing circa £150,000 to the pilot scheme.

“We are monitoring the pilot closely and any decision to extend or continue this scheme will not be made until a final evaluation report has been completed in spring 2008.”

David Edwards, development officer for the Heart of Wales Line Forum, said, “There were a few teething troubles but things have now settled down and we are seeing over 1,000 journeys a week on the line under the scheme.

“By encouraging people to use public transport we achieve a number of benefits. Firstly we provide mobility to the many who don’t have access to a car, and we’ve heard positive comments about how it has improved their quality of life.

“Secondly, we’re bringing business to the many small communities along the line who depend on tourism. And doing this without adding to road congestion.”