Pressure is mounting on High Speed 2 (HS2) bosses to cut costs by reducing train speeds.
As project promoter HS2 Ltd looks to reduce its costs, a leading economist and a top rail academic have called for train speeds to be capped at 320km/h instead of 360km/h.
HS2 Ltd is facing cost pressures on main civils packages to build the line so that it can keep within ts £56bn budget. Last week New Civil Engineer revealed how the company had comissioned Aecom engineering director Mark Raiss to carry out an independent cost cutting study.
The route alignment for HS2 is being designed for 400km/h trains, with trains limited to a maximum speed of 360km/h or 320km/h in tunnels.
But National Infrastructure Committee commissioner and economist Bridget Rosewell has told the House of Lords economic affairs committee that said she had never understood why the new high speed line was looking to run trains at 360km/h.
“Speed isn’t irrelevant, I don’t want to say it’s just about capacity and it’s not about speed, but I’ve never understood the need for very high speed,” Rosewell said, “I’ve said this right at the very beginning back in 2008/09. I don’t see why we are privileging at 400km/h for the cost that that would imply.”
Rosewell added that designing the line for 400km/h constrained engineers’ ability to “sensibly” plan the route alignment.
“That was the top priority [to design for 400km/h] and then everything filled in after that,” she said. “It was a mistake.”
High speed trains in France and Japan operate at 320km/h. Rosewell added that the 360km/h speed limit would produce a time saving of only two or three minutes on services running at 320km/h.
“A matter of two to three minutes saving seems implausible that we could ever justify that,” she said. “I see no reason to go faster than the French TGVs, I think it’s silly.”
Southampton University professor of geotechnical engineering and track expert William Powrie told New Civil Engineer that reducing the speed limit to 320km/h would save money by eliminating the need to run trains on a concrete slabtrack base, allowing track to be laid on cheaper ballast.
New Civil Engineer revealed in September 2016 that slabtrack was the final choice of trackbed technology for the first phase of the line after heated lobbying. Proponents of slabtrack system had argued that ballasted track systems are noisy in use, expensive to maintain and even pose safety risks with individual ballast particles liable to be dislodged by the turbulent air caused by the passing high speed trains.
Conversely advocates of ballast-based systems had pointed to the much lower cost and flexibility in use afforded by such systems.
“If they did do ballast to start with, it would not be a disaster, you would still get the benefits. But it comes down to what can be afforded,” said Powrie.
Both systems are in use on modern high speed railways around the world. Japanese, German and Dutch high speed rail networks tend to be based on concrete slab track. But French and Spanish lines tend to be ballasted.
The first phase of High Speed 2 arguably lends itself to slabtrack as a high proportion of the route is in tunnel – where slabtrack has already been specified as the trackbed of choice. This is a simple economic decision as slabtrack systems require a shallower base which means the tunnels can be smaller in internal diameter.
New Civil Engineer understands a change in speed would be possible within the scope of the hybrid bill. According to a source, the focus of the bill is on the design envelope of the project rather than specific operational constraints like train speeds.
However, the government has previously said that the business case for the line could be compromised if the journey time was increased as a result of cutting train speeds and the Department for Transport will have the final say on any speed adjustments.
A DfT spokesperson said there were no plans to lower the speed of the route saying the higher line speed would deliver long-term benefits to HS2 passengers for years to come. It added that the track type had been based on the weight of the trains passing over it, not the speed of the trains.
“HS2 is already underway with 7,000 people and 2,000 businesses working on building what will become the backbone of Britain’s rail network,” said the spokesperson. “Track material is chosen based primarily on tonnage of traffic, and not on speed. There are no plans to lower maximum speeds across the route.”
The DfT is currently procuring high speed trains capable of running at 360km/h with all the railway systems – track, signalling and overhead line power supply – also designed for running at 360km/h.
An HS2 Ltd spokesperson said: “HS2 Ltd continues to work to the scope and budget requirements that have been set out by government. We are working with our supply chain to drive efficiencies and economies of scale across every part of the project.”
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