The Forest Owners Association says the economy is losing money ever month because of the slow and uncertain process of upgrading roads.
A law change in 2010 allowed for longer and heavier trucks to take larger loads, in an attempt to reduce congestion and vehicle emissions, and increase road safety.
The Transport Agency says $45 million will be spent upgrading bridges and tunnels on highways over the next four years to accommodate bigger trucks.
Some $15 million will be spent fixing bridges on lesser roads, if councils agree to split the cost of the upgrade.
But the Forest Owners Association is worried councils will not want to burden ratepayers.
Chairman Brian Pritchard says it is possible the forestry sector could share some of the cost of the roading upgrades.
