Drivers on the West Coast face detours of more than an hour tonight, while a bridge is closed for work.
The Taramakau Road rail bridge on State Highway six near Greymouth will be shut from 8pm, for twelve hours.
The Transport Agency said it was so rubber mats could be installed to improve safety for cyclists.
The agency said detours were available through Jacksons, Stillwater and Moana, which would add about 90 minutes to travel times.
The road will be closed for another 12 hours on Saturday 27 June.