''Mainly it's just for the extra time, fuel and staff costs,'' he said.
While some operators could be charging a ''one-off levy'', on a case by case basis, such as time-sensitive freight, Mr Robertson believed the best and most popular cost modelling was the per kilometre charge.
Trucking association chief executive David Boyce understood that while operators were still negotiating, the per kilometre charge was ''about 20%'', to use the inland route.
Other routes around the country, including Dunedin to Christchurch, should not be affected, he said.
He believed that while the inland route would have to be used for many more months, alliances between ports, KiwiRail and shippers would in the near future offer more freight options.
Pacifica Shipping chief executive Steve Chapman said when contacted no second vessel from overseas was on its way, and it was ''premature'' to be considering that option.
While the first week following the earthquake was ''a mad house'' of people ordering space, going into the second week was ''a more uniform approach'', with bookings up more than 30%, Mr Chapman said.
Pacifica's Spirit of Canterbury would continue on its present seven-day, four-port rotation; between Auckland, Tauranga, Nelson and Lyttelton, with no time to make calls elsewhere.
Aside from the Spirit of Canterbury, Mr Chapman said Pacifica would work with its international shipping partners who could deliver domestic containers around the ports on their present routes.
Of concern to both the transport and trucking associations was the effect of the extra ½ two and a-half hours on the journey and the drivers' ''driving envelope'', which was a 14-hour day, including mandatory stops.
Mr Robertson said the alternate Christchurch-Picton run was ''pushing'' the regulatory envelope, depending on start times, and having to use a second driver would also push up costs.
He also noted that with one road, instead of two, now carrying all freight and international tourists, and soon New Zealand holidaymakers, extra care would have to be taken, and especially by touring cyclists using the open road.