Short line railways and tram systems which are designed to operate within urban zones are likely to have similarity to each other in design and operating specifications. This section sets out the rationale which led up to the Class 139 Stourbridge light rail design which has performed in satisfactory manner since 2009 over a full 7 years Rail Franchise contract. In the course of that lengthy service period in which over 4 million passenger journeys have been provided, the technology has yielded detailed economic data justifying the case for substituting previous heavy rail operation by an innovative lightweight form of rolling stock. Envisaging future projects, each application will be different but having hard information to start with it will be possible to arrive at good robust assessments of the capital and operating costs of prospective future ventures of a similar nature.
Evidence is therefore now available for assessing the case for substituting previous heavy rail operations on lightly used lines by innovative lightweight rolling stock which is propelled by means of a very low carbon prime mover and driveline while employing personnel who are not expected to have to cope with the more exacting requirements of the main parts of the heavy rail network. Rolling stock maintenance is also much lighter in character and less expensive.
Low Capital Investment
There has existed for some time a standard approach applied to the modernisation of railway lines This has been to introduce electrification. In the case of individual local lines, operators would normally plan to convert the heavy rail operation to LRT (light rapid transit) incurring lower investment that fully-fledged heavy rail electrification. For many situations, though lower, LRT costs are still prohibitive. Taking Stourbridge as an example, to have converted the Town Branch line to LRT might have cost in excess of £10 million, counting track renewal, 750v electrification, new rolling stock and building an appropriately-equipped depot adjacent to the line. By opting to leave the original track in place and to operate with hybrid technology the railway planners have still provided clean, modern operating circumstances but the investment required has turned out to be under 15% of a LRT conversion. Having a less than ideal track with most of the materials dating back to the days of the Great Western Railway, has meant a poorer ride quality than if the track had been relaid with continuously welded rails rather than the multiple joints of traditionally constructed track, and this is a point to be considered with future projects, but passenger satisfaction has nevertheless been consistently high. Poor track increases wear and tear on vehicles but in the case of the Stourbridge operation, a careful and resourceful maintenance regime has resulted in reliability of over 99% in every one of the full operating years.
Building a modern tramway using an electrified infrastructure is a time consuming and very expensive process as can be seen in the photograph to the left. The contractors have had to dig deeply below the original road surface in order to divert all of the services such as power, water and computer networks.
With a hybrid system, it will rarely be necessary to disturb any of this historic infrastructure which reduces the capital investment by an order of magnitude.
The hybrid innovation has provided good energy efficiency as a result of the vehicles being able to be propelled with very small 2.4 litre engines without sacrificing performance, (the energy boost available from the flywheel provides excellent acceleration) Fuel consumption is less than the equivalent of one gallon per hour with the extra benefit of energy regenerative braking (when the railcar slows down approaching a station instead of applying brakes energy is recovered by speeding up the flywheel). Despite the generous provision of a two person crew, so that no-one is needed at stations to despatch the service, labour costs are reasonable as a result of being able operate with staff pay grades closer to light rail rather than heavy rail levels due to the less demanding nature of the tasks operating a service on a simple branch line with no mixing with other rail traffic. With components such as the LPG powered automotive engine being relatively small and easy to handle, the specially constructed and equipped depot is more similar in character to a local bus garage than a traincare facility as deployed on the main Network.
Preliminary assessments of the operating costs of passenger services on uncomplicated railways and newly-constructed light tramways based on PPM technology is that it will be possible to match or even achieve reductions on best practice using conventional technology but with the benefit of much reduced capital cost and with shorter timescales for implementation.
PPM railcars have applied the hybrid approach as a way of reducing the size and complexity of driveline components. A rail vehicle able to carry 60 people would normally be expected to have an 8 litre engine weighing at least a tonne. The Class 139 which achieves its good acceleration by drawing power from the flywheel has a small engine of just 2.4 litres. This together with all the other individual components and sub-assemblies can be handled in a small workshop at the branch where the vehicle runs, avoiding the need to travel through the network for depot support to a remote train care facility equipped with heavy cranes and other handling gear.
A special feature of the Class 139 railcar which is different from most rolling stock on Britain’s railways is the facility to have the floor of the vehicle at the same level as the railway platform. Normally there can be a full step height difference in levels which calls for platform staff to attend the boarding of a passenger using a wheelchair. Special ramps are stored at each station which must be deployed for this purpose frequently causing delay. Wheelchair passengers board Class 139 railcars without need of support from train crews or station staff.
Prior to the introduction of the Class 139 light railcars to the Stourbridge Town Branch the operating company provided the service using the mallest available heavy rail train, the single car Class 153 Super Sprinter. Though built over 30 years ago the Class 153 remain fully-serviceable and in great demand on the main network, so instead of being scrapped they have been added to extend the length and capacity of more modern trains in response to the growing demand for rail travel. On a small branchline these trains weighing over 40 tonnes and with 14 litre diesel engines incur more than twice the running cost of the new PPM units.
Light rail systems that have been introduced into several British cities over the last 30 years have been very popular and have benefitted the economics of the host city. However in the previous phase of tramway construction from the end of the 19th century to early in the 20th it was possible to install systems in a matter of months because the subsoil of the streets did not have today’s complex array of utilities, such as gas, water, electricity and cabling for TV and computer networks. With electric traction requiring current at 750v DC it is inevitable that construction of a new tramway will require much of the apparatus in the subsoil to be re- located involving great expense and construction programmes taking several years. This will not be necessary if the PPM hybrid system is adopted.