Forth Replacement Crossing - Report 1 - Assessment of Transport Network
4 FORTH BRIDGE AND ASSOCIATED RAIL NETWORK
The recently published Network Rail (NR) Draft Route Utilisation Strategy (RUS) issued for consultation highlights that improved use of rail capacity is a central element of the Scottish Executive’s plans for effective delivery of its rail transport objectives. The key requirement is to make effective and efficient use of the current route capacity.
Rail passenger demand has increased significantly in the last few years reflecting increased employment, especially in Edinburgh, and as a consequence of increasing road congestion especially over the Firth of Forth.
One of the key issues to be addressed is the rail capacity through the Forth Bridge corridor where significant overcrowding is experienced on peak hour trains.
Current passenger services include:
First ScotRail express services terminating at Aberdeen, Dundee, Markinch and Perth;
Operated by First ScotRail; and
GNER/Virgin services to Dundee and Aberdeen.
There are presently 10 trains per hour crossing the bridge between 0730 and 0830 i.e. five on the Up line and five on the Down Line
Currently the Edinburgh to Aberdeen services provide uncompetitive end to end journey times and the current Fife Circle services have no scope for recovery of any late running incurred on their outward journey due to their circular nature. Passenger demand to Edinburgh is predicted to grow and the current combination of infrastructure and train service will not meet this demand.
The railway infrastructure on the Forth Bridge consists of double track with three-aspect signalling (with five minute headway4), allowing operation in both directions on either track. However, it is normally used as conventional double track. This ‘bidirectional’ signalling is primarily for maintenance purposes, when it is used to permit trains to run in either direction over the same section of track subject to the built-in safety systems which prevent collisions. The bridge is also the longest section with regard to signalling between Edinburgh and Inverkeithing and this further limits its capacity.
The NR - RUS Table 19, Baseline Gaps, states that restrictive signalling headways between Edinburgh and Fife, particularly across the Forth Bridge limit the number of trains that can operate over the corridor and result in increased delays during perturbed running. There are also difficulties in accommodating the current mix of express services and all station stopping services.
4.3.2 Route Capability:
The following sections detail the various parameters governing the operation of the railway on the Forth Bridge:
- route availability5 is RA8 load/gauge capacity. The NR RUS states in 220.127.116.11 Route Availability (RA), that the RA of a specific route is restricted by the carrying capability of both its structures and its track. Very few of the routes in Scotland are capable of carrying RA10 traffic. Most current passenger only routes are RA5 or less and a number of routes which historically only saw a sprinter train service but now see limited mixed traffic are RA5;
- ruling line speed is 90mph. However, the Forth Bridge is constrained by a 20mph speed restriction for freight traffic and 50mph for passenger trains;
- load gauge is W76;
- no electrification;
- platform lengths on stations along the route corridor (Fife to Haymarket) is a minimum 6 x Car Class 170 DMU7 (142M) throughout;
- capacity utilisation - is the number of trains that operate over the bridge in the busiest hour;
- practical capacity –recommended 9 paths per hour. Current peak demand is 10 paths per hour. Peak utilisation is therefore 111 per cent between 0800 and 0900;
- theoretical capacity – theoretical capacity is 12 paths per hour, with peak utilisation 83 per cent;
- the route is the tenth worst in Scotland with regard to the total overall reactionary delays with 24802 minutes delay and third worst for total overall reactionary delay ranked by train mile with 352.5 delay minutes per train;
- the route operates at a high utilisation level outwith the peaks which prolongs the recovery period following any disruptive event; and
- the main restriction on the Forth Bridge is that freight trains headcode 7Gxx (loaded coal class 7 freight train, maximum speed 45mph) must not be timed to pass another freight train on the opposite line on the Forth Bridge. This is from the Rule of the Plan(ROP)8. The restriction could also reduce capacity by the addition of pathing time to freight services which could delay other trains. In practice the timetable planner should ensure that freight trains are programmed to pass away from the bridge so that capacity is not compromised.
4.3.3 Bridge Maintenance
One of the major issues is that the Forth Bridge is a listed structure, and any new infrastructure must allow safe access for maintenance. There are restrictions due to its listed status as to what alterations can be made to the bridge; for example, Historic Scotland do not want any new walkways on the outside of the bridge that would alter the appearance. This is in direct conflict with HM Railway Inspectorate (HMRI), who want new walkways to improve safety for maintenance activities. To date it has been impossible to reconcile the two parties, and the status quo has been maintained.
In the late 1990’s Network Rail was under severe pressure from heritage bodies to improve the condition and appearance of the bridge. At the time the issue was that parts of the bridge were inaccessible on safety grounds, and therefore had not been maintained in good order. However, in 2001/02 Network Rail engaged Balfour Beatty to repair/replace the corroded elements. This included sandblasting the structure and then protecting it using a steel-fibre paint, more commonly used on oil rigs. This work is still ongoing.
The day to day issues of maintaining the bridge structure are still accessibility, logistics and safety implications of working on the bridge whilst maintaining train services. The bridge was shut for seven days in the summer of 2005 to carry out major repairs.
Network Rail has estimated the life of the bridge to be in excess of 100 years. However, this is dependant upon NR’s inspection and refurbishment works programme for the bridge being carried out year on year.
4.3.4 Current route improvements being undertaken by NR
NR is currently carrying out small signalling improvement works to improve signal overlaps between Edinburgh and Inverkeithing. This will not allow further train paths and should improve performance of the existing services. This work is being done in three stages; the first of which is currently being implemented, the second and third phases will follow. At the present time phase two has funding in place, however, phase three is currently not funded. NR are confident that this will be in place to allow the work to proceed after the completion of phase two. The timescales for the three stages to be complete is currently 2010-11. The results of these improvements will be a reduction in headway time from five minutes to three minutes.
4.3.5 Areas to be explored to improve performance and or increase train paths
Listed below are some of the options that can be explored. This is not an exhaustive list, and will be added to as the appraisal process is developed over the coming months:
- review of the Allocation of Timetable Slots to different classes of trains. NR has already held discussions with First ScotRail on this option, and has received agreement that this should be developed and taken forward for implementation;
- re-signalling the route between Edinburgh Waverley and Inverkeithing to improve signalling headways by introducing additional signals. This would offer increased capacity which would allow the re-pathing of additional trains and improved performance;
- longer platform lengths at stations. This would allow longer trains to operate on the routes;
- improve differential in train speeds/acceleration of train. When timetabling services the capacity of a route can be maximised if trains of equal characteristics (i.e. acceleration, braking, top speed) are grouped together especially during peak periods;
- flighting9 of services to ensure that all trains have the same operating pattern approaching and leaving the bridge;
- revise train stopping patterns to optimise train paths over the bridge;
- the impact of the proposed Edinburgh Airport Rail Link and the Alloa to Kincardine and Waverley projects currently being constructed must be fully explored to maximise the benefits of re-routing and re-timetabling of services over the rail bridge;
- electrification of the route would improve train performance through better acceleration. The likelihood of the bridge being electrified would be slim as there are a number of constraints with regard to clearances to the existing bridge structure required to accommodate the overhead wires and associated steelwork; and
- track upgrade on the Fife Circle, particularly between Thornton and Inverkeithing via Dunfermline (see Figure 4.1 – below), to permit higher line speed which could allow additional capacity over the route.
Figure 4.1: Railway Stations on Fife Circle and between Edinburgh & Falkirk
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