Dublin's Dart service has been closed to the south side over the summer weekends to accommodate upgrading work and improve facilities for disabled passengers.

Bus services near the southern Dart line have been doubled at weekends to transport the extra passengers, and this month the service will be reopened during the weekends of the Bray airshow and Dún Laoghaire's Festival of World Cultures.

However, businesses and commuters along the Dart line have expressed concern at the current weekend closures, with seafront retailers in particular noting a drop in trade.

Iarnród Éireann worked with the Bray Chamber of Commerce to promote the area this summer through radio adverts, posters and leaflets, but a chamber spokesperson said that local businesses along the seafront had reported a 25 to 30 per cent downturn in trade compared to the traditional holiday period.

Margaret Dunne, manager of Dalkey Castle and Heritage Centre, said visitor numbers had dropped from 40 or 50 guests a day to 8 per weekend.

"There is a shuttle bus provided, but people look on the Dart journey as part of the visitor experience," she said. She expressed dismay that the improvements were affecting a second summer. "Of course we're in favour of transport accessibility for all, but these works should have been done in one fell swoop."