Greens MLA Shane Rattenbury at the ACT Legislative Assembly during question time.

RIGHT TRACK: Shane Rattenbury says his party wants to see rail upgraded. Photo: Jeffrey Chan

The ACT's road network, including bridges, would need to be assessed before over-sized B-triple trucks were allowed into the territory.

Minister for Territory and Municipal Services Shane Rattenbury said if a proposal was put forward for Canberra after a trial in NSW next year, a freight hub on the new Majura Parkway could be considered, where big trucks would stop on the edge of the city and transfer freight to smaller ones.

But Mr Rattenbury, the Greens balance-of-power minister, says his party wants to see rail upgraded to enable as many trucks as possible to be taken off the road.

The NSW government is considering a trial on the Hume Highway between Sydney and Melbourne next year for the 35-metre road giants which comprise three trailers, in addition to the two-trailer B-doubles which operate today. Interstate freight companies in Canberra see no reason why B-triples could not be used to deliver bulk freight, such as fuel, more efficiently.

Mr Rattenbury said the ACT would first need to investigate which roads would be capable of accommodating the longer trucks.

B-doubles are allowed on national highways and main roads in the territory to deliver freight to industrial suburbs, petrol stations and supermarkets.

Canberra Airport's 20-year master plan includes a freight hub and anticipates trucks to increase with air freight services.

The plan says: ''Up to 10 trucks [B-double or equivalent] may operate to Sydney in association with increases in the overnight express freight system, along with two to three B-double services per night to Melbourne. Smaller vehicles may also commence regional truck services to complement regional air freight operations.''

Mr Rattenbury said his view and that of the Greens was focusing on improving rail networks, rather than permitting B-triples.

''It is clear that freight is increasing and we should be aiming to take as many trucks off the road as possible.

''Right across NSW particularly and therefore into the ACT rail infrastructure has been allowed to degrade. It hasn't been been maintained and that has pushed more and more trucks onto the road,'' he said.

Mr Rattenbury said the government would wait for the outcome of next year's trial before taking any action.

''As I understand it, the intent is to set up a corridor with a freight hub outside Melbourne and basically run them up and down the Hume Highway,'' he said.

''There has been no discussion of coming into Canberra at this point.''

If talks on bigger trucks continued, the ACT would take a similar line as Sydney and Melbourne, where authorities would not allow B-triples on the streets of the city.

''You would be looking at a freight hub sort of area, it would be somewhere like the Majura Road once it has been upgraded, in a similar way to what they are talking about for Sydney and Melbourne,'' Mr Rattenbury said.

From the hub, freight would be transferred to smaller trucks and distributed.

Mr Rattenbury said rail networks had been going backwards. The Greens had been critical of the recent switch from rail to roads hauling fuel into the ACT.

''Many people would rather see fuel on a train line than on heavy vehicles on the road,'' Mr Rattenbury said. ''Clearly there is a range of costs attached to truck transport, their impact on roads.

''They are a key source of damage to surfaces and therefore increased road maintenance costs.''

He said trains were better for the environment and safer than cars having to share the road with trucks.

Since 2010 at least seven B-doubles a day have been delivering bulk fuel into Canberra. Much of the fuel storage sits alongside disused rail lines in Fyshwick. The rail line is near bulky goods stores.