Light rail: would it be resilient during an earthquake in Wellington?
Light rail has been chosen as the best option for getting Wellingtonians across the city for decades to come, but some fear the tracks won’t withstand natural disasters.
The new transit line is part of Let’s Get Wellington Moving, a public transport and infrastructure transformation program set to come into play over the next 30 years.
The government, along with Wellington city and regional councils, have named their preferred plan, which will cost $7.4 billion and include light rail from the station to Island Bay.
Critics of light rail say it is too expensive, too rigid, and too vulnerable to damage from earthquakes.
Brent Efford of the Light Rail Transit Association said the lack of resilience was “a lie that anti-light rails often trot around”.
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In past earthquakes — San Francisco in 1989, Wellington in 1942, Napier in 1931 — streetcar tracks suffered very little damage, Efford said. After the February 2011 earthquake, the Christchurch Light Rail was “operational and once again an icon of the city, while most of the city center lay in ruins”, he said.
The solid high-strength steel rails were much stronger than reinforced concrete. “Even across a fault line, the rails would fare better than the surrounding roadway,” Efford said.
If the rails crack or shift, it would take “a few hours of work with the right equipment to fix them.” “Anti-rails paint this picture of tram rails sticking out of the ground and making the streets impassable. It’s just pure fantasy,” Efford said.
Greater Wellington Regional Councilor and Civil Engineer Roger Blakeley was assured of the resilience of the light rail. The rails, driven into the ground, moved with him, he said. “You’re only at risk for damage if there’s fault line movement along the tracks,” he said.
In Wellington, the most likely scenario would be a landslide along the Wellington-Ōhāriu fault line, which runs along Thorndon Ravine and Hutt Road. It moves about once every 500 years and its last move was 150 years ago.
“There are no known faults that cross the line of [the proposed] road,” said Blakeley, who is chairman of the regional council’s transportation committee.
Transport Minister Michael Wood reveals the government’s preferred option, Let’s Get Wellington Moving, which includes both a light rail and a second Mount Victoria tunnel.
The other risk was liquefaction, in which soil behaves more like a liquid than a solid in an earthquake – usually in sandy soil. The most risky areas of the route would be the quays and Wakefield Street, as well as the northern part of Cambridge Terrace.
However, liquefaction would also disrupt road foundations. “If it was a light rail route or a bus rapid transit route, the risk would be the same,” Blakeley said.
Proponents of bus rapid transit argue that it would be easier to reroute a route away from damaged areas. But Blakeley said there was really only one suitable road between the basin reserve and Island Bay: Adelaide Rd, the proposed route.
The success of Let’s Get Wellington Moving hinges on building more houses nearby. “The international evidence is that light rail is attracting more development investment along the routes,” Blakeley said.
The flexibility of a bus route could also be its downfall. “If you invest hundreds of millions in a residential building along the road, you want to be sure that the road will be there in 10, 20 years,” he said.
Wellington City Councilor Sean Rush said trackless vehicles provide that flexibility, but we’ve taken that risk with the train lines north of the city.
Earthquakes aside, all modes of transportation will be vulnerable to the effects of one threat: climate change.
Rising sea levels were a threat to infrastructure along the waterfront quays, Wakefield St and Cambridge Terrace, while Cobham Dr, the proposed location for a new bus route to the eastern suburbs, was vulnerable due to “potential lateral movement in the bay” – put simply, the ground could collapse into the sea.
Planning for those contingencies would be “an essential part of the detailed business case,” Blakeley said.