A combination of bad weather and KiwiRail's asbestos problems is causing difficulties for freight companies.
KiwiRail took 40 train engines out of service after it discovered asbestos had been sprayed on parts of the locomotives, while recent bad weather has caused ferry cancellations.
The Road Transport Forum says high-volume products such as milk and wine are transported by rail and there aren't enough road tankers to fill the gap left by the withdrawn freight trains.
Chief executive Ken Shirley says the problems are also affecting suppliers and growers, with some products being stockpiled at the farm gate.
"There's huge volumes of wine and there's a lot of milk moved on trains and if you don't have the capacity of KiwiRail with their tankers, then there just isn't sufficient road tanker to perform the task."
Transport firm Mainfreight fears the asbestos problem could cause long-term delays.
It says it doesn't know how long the trains will be out of service and is urging KiwiRail to find a solution quickly.
Trucking company Big Chill Distribution is more concerned with ferry cancellations caused by bad weather, saying they could put at risk entire loads of perishable goods.