The rail network needs to be able to carry a 39 percent heavier weight than it now can, according to a study released this week. Do the math. Most of the network can currently carry 18 tonne axle loads. A six axle locomotive can therefore weigh a maximum of 108 tonnes and a four axle locomotive can weigh 72 tonnes.
Modern diesel-electric locomotives built for New Zealand's 1067mm gauge railway weigh more than 108 tonnes. The newest locomotives on the Queensland network weigh between 119 and 120 tonnes.
The figures are in the National Freight Demands Study released by the Ministry of Economic Development this week. The study gives a comprehensive rundown of what needs to be done to fix up the rail network and trains now in government ownership.
The 18 tonne axle load is a limiting factor. The network must be built to be able to carry a 25 tonne axle load, a 39 percent increase.
"It costs relatively little to design and build bridges for heavier loads, so code reviews are currently taking place so that new bridges will be built to carry 25 tonne axle loads," the report said.
A programme is under way to replace 2900 wooden piers in 521 bridges.
The report says KiwiRail, the train and ferry operator, is buying 100 new container wagons mostly for traffic between Tauranga and Auckland capable of a 20 tonne axle load.
Ontrack, the track operator, is actively looking at improving the Auckland to Hamilton line so it can carry 20 tonne axle loads and eventually 22.5 tonne loads. Hamilton to Tauranga will be next.
"Extending this to other routes would require significant expenditure," the report said.
Another issue is getting higher containers through tunnels built in the 19th century. The restriction is height rather than width of tunnels though height and width interact if a tunnel roof is curved.
Some lines cannot take 2.90m high containers, the modern "high-cube" standard. Most of the main lines can with the exception of Greymouth to Christchurch and North Auckland.
On the Auckland to Tauranga and Invercargill to Port Chalmers routes 3.05m high containers are used for dairy products. The containers can take a double stack of pallets.
"Further work to extend the use of 3.05m containers throughout the network is feasible but is not currently planned," the report said.
If Marsden Point is to become a significant port the Makarau tunnel would have to be replaced and 12 other tunnels between Auckland and Whangarei improved.
There are also plans to remove the first tunnel on the Rolleston to Arthur's Pass route on the Midland Line to improve clearances and speeds.
The rail line also needs to be realigned in places in much the same way that roads have been realigned over the years.
Current thinking includes realigning the line from Otaki to Manakau, a deviation from Kakariki to Porewa to avoid steep grades into Marton and easing a sharp curve north of Taihape. Easing of steep grades on the coal route at Reefton, Cass and near Springfield are longer term options.
Busy routes need to be double tracked especially where there are passenger services so freight trains can get through. The capacity of the Papakura to Hamilton line is limited by two single tracked sections from Auckland to Te Kauwhata and across the Waikato River at Ngaruawahia.
On the Hamilton to Tauranga route crossing loops are being extended to 900 metres and two new loops are being constructed at the cost of $10 million.
Replacing of signalling would increase the capacity of the Midland Line between Christchurch and the West Coast and improve speeds.
The report does not say how many new locomotives are needed but it says because of increased passenger services there are sometimes no locomotives available to carry freight.
The report also says that part of the closed Rotorua branch line near Putaruru is being opened to serve a water bottling plant.
"The remainder of the Rotorua branch may be reopened for passenger use if local plans to run passenger trains come to fruition," the report said.
NZPA
source: newshub archive
