A freight train with a mechanical fault held up traffic at the Maheno level crossing for about 20 minutes on Sunday night.
A KiwiRail spokesperson said at 7.10pm, the northbound freight train was stopped at the Maheno level crossing.
Following an inspection, a locomotive engineer detected a fault with the coupling between two of the wagons on the service.
Staff were called to assist and fix the coupling on site, before the freight train was cleared to continue north to Christchurch.
''Traffic was help up for approximately 20 minutes at the level crossing and KiwiRail apologises for any inconvenience this may have caused drivers,'' the spokesperson said.
