A stop/go system has been put in place at the Navvy bridge in Arklow following an accident in the early hours of Friday morning.
A car stuck the bridge which passes over the Dublin to Rosslare railway line just after 2am.
A large section of the bridge ended up on the railway-line such was the impact.
Iarnród Éireann maintenance crew who were working on the railway line at the time heard an almighty bang as the granite blocks fell on to the track, it is understood damage was caused to one of the tracks.
Arklow fire services attended the scene and Gardai arrested a man.