The UK government set up High Speed 2 (HS2) Ltd in January 2009 to consider the case for new high speed rail line between London and Scotland capable of carrying passenger trains at speeds up to 250 miles per hour. The broad plan for the network to Manchester and Leeds including the section between London and the West Midlands is roughly the shape of a letter Y. The “Service specification assumptions for the Y network” shows a total of 18 trains per hour (tph). The government and its consultants, HS2 Ltd argued that HS2 rail network would ‘transform the country’s economy geographically’, bringing Britain’s major cities closer together. Feasibility of HS2 Y Network
HS2 plans to design a track that will be capable of running up to 18tph, each carrying up to 1,100 passengers and operating at speeds of up to 250 mph, to run between these cities and serve other destinations via links to the existing “classic” rail network. HS2 hopes to reduce journey times between London Euston and central Birmingham from 84 to 49 minutes. One of the key arguments put forward by the government in support of HS2 is that it is the only effective way of increasing capacity on the rail network. 1.
The institute of Railway Operators’ definition of capacity, adopted in the Department for Transport Rail Technical Strategy is; ‘The number of trains that can be incorporated into a timetable that is conflict free, commercially attractive, compliant with regulatory requirements, and can be operated in the face of anticipated levels of primary delay whilst meeting agreed performance targets’. This definition emphasises the dynamic nature of capacity and identifies the fundamental factors that affect it. The factors that I consider may impinge on HS2’s capacity of achieving 18tph includes: the design of station terminals and their approaches, the dovetailing of services at junctions, the practicality of rapid boarding at intermediate stations and the impact of potential delays on those sections of the classic network that would be used by HS2 among others. Current plans for Y would see 18tph and per direction at 250mph, a feat that has not yet been attempted on any existing railway. Headway is paramount to the question of line capacity. If a sufficiently low headway cannot be maintained in all circumstances, running 18tph would not be feasible. For each line in the Y network, the signalling system will determine the headway so far as the signalling are located exactly as required to provide the braking distance for the intended speed. The rolling stock will actually run at that speed, the theoretical headway will be very low, achieving the intended line capacity. There may however be other factors along the line that may militate against how the signalling system is placed, which may lead to longer sections, hence longer headways. The headway must be set for the convenience of planning the timetable and some allowance made for the robustness in practise. Meeting capacity targets is very much dependent on traffic mix. The ideal case with regards to the Y network is when all trains will be the same or have the same speed. Only high speed trains should use HS2: running slower trains on the line would reduce the numbers of trains that could run per hour. When different train mixture increases, more interference will be generated, and as a result trains would require overtaking and crossings, the mixture then will in effect reduce the traffic flow. Terminal capacity of the proposed Y network can pose a major binding constraint on the feasibility of the proposal. Trains would need to turn back at terminal stations, and achieving this depends on the turnaround time and the number of platforms. The ability of terminals to accept, turn and dispatch trains is very crucial. HS2 Ltd suggests that London Euston is the most satisfactory London terminal for HS2. The choices of Old Oak Common and Birmingham Interchange as interchange stations, and...
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