Interaction between Heavy and Light Rail

Conventional heavy railways are an asset when its theoretically high passenger and distance capacity is actually required, so it makes sense therefore that the existing heavy rail services concentrate on more strategic inter city routes. However, the proposed Edinburgh Light Railway Company Limited (ELR) light rail train network would use sections of the existing heavy rail operational lines in and around Edinburgh. In the ELR proposal an extension to the existing Edinburgh Cross Rail route is envisaged as a new strategic link from Newcraighall via Millerhill, the Edinburgh Royal Infirmary (ERI), joining the Edinburgh South Suburban Railway (ESSR) westbound at Peffermill and onto Balgreen junction and it would seem logical to use existing Cross Rail rolling stock.  In this circumstance an example of sharing track with light rail trains as appropriate despite the differing buffing loads of light rail and heavy rail rolling stock. Technical progress means that appropriate safety arrangements can be put into force for mixed service running.

There is no reason why this type of light rail train operation would not integrate successfully with the heavy transit mode in terms of the track sharing proposed. The aim is to have independent systems as much as possible so that they would not interfere with, but complement each other in delivering what each system is best designed to do.

Cost savings are an incentive to mixed heavy and light rail train operation. Despite the potential economies to be gained, extreme caution has been shown to date in the UK to what would be a unique opportunity for this type of dual operation. The long-delayed first trial of a tram-train in the UK has been pushed back until at least 2017, in the North of England.  Project timescales have been revised to incorporate the comprehensive design works needed to adapt the operational heavy rail network to allow tram-train vehicles to run on it.  In simple terms, the tram-train concept allows a railway vehicle to run in two distinct and continuous operational modes and environments, serving both relatively dense city centres as an on-street tram, and areas further from the city as a commuter train. The concept has some definite advantages to it, but it also requires a greater deal of regulation than either modes do on their own. The concept was pioneered in Germany some years ago and has now begun spreading to other regions of Europe.

Of course, not all models have to be the same and in the case of the ELR proposal it is slightly different in that light rail trains, not tram-trains would be running on this network and virtually no on-street running, apart from a short stretch between the proposed ELR stations at Dock and Lindsay Road, near Ocean Terminal.

The tram-train concept allows a railway vehicle to run as an on-street tram serving city centres and also as a commuter train running on existing local rail networks. Any subsequent electrification of existing main lines would see them capable of operating at both light and heavy rail operating voltage.  The pilot scheme is scheduled to run for two years followed by a detailed evaluation and if transport authorities decide to wait until the conclusions become available before developing their own proposals, it would without a doubt be many years before services could begin.

While the tram-train is fundamentally a proven concept in continental Europe, you have to take on board local requirements and start thinking about what you actually need.  A light rail train network is a very good way to improve local passenger services, using both existing operational rail lines and new ones to avoid the need for expensive works on constructing new tram-train alignments on city streets.

In Tyne & Wear, where high-platform light metro cars and heavy rail trains, also with high floors, are involved in heavy rail track sharing and operate successfully, although a gap between the platform and the floor levels currently exists. Similarly, on operational heavy rail a “gap” exists on platforms, although the intention would be for ELR light rail train floors to be level as much as possible with the platform, so that the system would incorporate full safety and accessibility facilities, allowing step free access.

On the Docklands Light Railway in London the vehicle cars are high-floor and stand level with the platform edges to make boarding easy.  The designs of these vehicles, based on a German model were originally intended and indeed used in systems with elements of street running, albeit they had high-floors.

In general, sharing track like in the ELR proposal, could mean mixed running of passenger rolling stock with similar floor levels. Obviously, the light rail train platforms would make up the majority of the ELR urban system, so being realistic the existing heavy rail platform levels should remain unaltered and the construction of similar level platforms on the new ELR routes would on balance seem both sensible and feasible.  There would be no intention to share track with the existing low level tram route, however, where appropriate, close proximity in terms of linking at strategic road/rail/tram interchanges would obviously be paramount although each means of transport provided would be operating independently in terms of road or track, while at the same providing important connections and choices in the network for travellers.

Of course, freight, non-stopping heavy rail passenger and other trains use the Edinburgh South Suburban Railway (ESSR) and other operational lines frequently, and often in a greater frequency when works on other parts of the network demands re-routing. Opening and closing safety doors could be installed on certain platforms at certain stations where heavy rail trains, pass regularly and are not stopping.

Existing operational lines will obviously require some work to be done to them, particularly to accommodate the amalgamation of the lines at new interfaces as well as work related to new stops.

In terms of modern light rail technology, light rail trains and tram vehicles look a lot like each other, although they come in various shapes and sizes. Any misunderstanding appears to originate from planning jargon where “trams” were seen as old fashioned whereas “light rail” is seen as trendy. In general, light rail, tram and tram-train vehicles are all very accessible.

It is envisaged that the ELR light rail train vehicles would be the latest low emission diesel electric engines that are economically efficient, reliable and environment-friendly, providing a rational way of moving large numbers of passengers to and from urban areas as they become an essential part of the thinking for a solution for mass urban rapid transport in Edinburgh today.

Using diesel electric power on the network of routes including existing operational lines eliminates substantial investment in overhead or ground level electrification, thus avoiding additional disruption and at the same time keeping the cost and justification of such a solution to a minimum.  It is fair to say that diesel-electric power units will be around for some time to come.

The choice to use diesel-electric power is both reasonable in terms of start up costs and the fact that the ELR proposal is fundamentally an off-road solution. The new breed of environmentally friendly diesel-electric power units would appear to be the best way forward.

At this stage in the process, various power design features could apply in different ways to a light rail vehicle.  As mentioned above, one option is to use the latest low emission electric engines and if some on-street running is incorporated, in this case between the proposed ELR stations at Dock and Lindsay Road, dual powered diesel electric, overhead current collection or indeed ground level electrification could be used.  These features could, if practical, also be applied to other sections of the ELR routes shared with cyclists and walkers.