A transport-lobby group is concerned KiwiRail's suspension of North Auckland rail services due to asbestos may become permanent, mirroring the fate of the Napier to Gisborne line.
KiwiRail has suspended all services on the North Auckland Line and reduced services on other lines throughout the North Island.
The move is a contingency plan, enacted after 40 DL locomotives were pulled from the tracks following concerns over cancer-causing asbestos.
Asbestos was found in a soundproofing compound used in the engine bay and around the cabs. However, no airborne fibres have yet been identified in testing.
Transport lobby-group, The Campaign for Better Transport, says it is concerned the suspension of services could become permanent.
In 2012, KiwiRail suspended services on the Napier to Gisborne line after storm damage rendered it commercially unviable.
"We need to keep the Northland network open for the benefit of freight and road users," campaign spokesman Jon Reeves said.
KiwiRail says it has moved a number of locomotives from the South Island to the North. But they do not have the same power capacity, meaning trains have to be shorter and lighter.
Although testing has found the DL locomotives do not pose an immediate risk to health, the fleet remains withdrawn from service while more testing is carried out this week.
The Rail and Maritime Transport Union says the primary concern is the safety of rail staff and the locomotives must remain out of service until they are confirmed to be absolutely safe.
The locomotives were built by Chinese company Dalian Locomotive and Rolling Stock Co.
KiwiRail says it sought and received assurances that no asbestos was used in the making of the locomotives from the manufacturer in 2013, following reports of asbestos in Chinese-manufactured locomotives in Australia.
The state-owned company says the use of asbestos was a breach of contractual specifications for the design and manufacture of the locomotives.
Dalian has agreed it breached the supply contract.