DART southside services could be back to normal by Wednesday after closing for repairs from flood damage.
The line has been closed between Grand Canal Dock and Sydney Parade due to erosion caused by the Dublin floods.
Technical experts warned Irish Rail that damage in the vicinity of a bridge pier at the Dodder Bridge, at the south end of Landsdowne Road station made it unsafe to use the line.
It had been expected that repair works would take until Friday next, but Irish Rail said today that "excellent progress" has been made so far.
Engineers will operate test locomotives across the bridge today "and subject to these tests being successful, the line would re-open in midweek," a spokesman said.
A re-opening time is expected to be confirmed tomorrow.
During the rains, at least two large trees were swept downstream by the River Dodder and were lodged under the bridge.