Findings and Benefits - Modification of the 3rd rail system to bottom or side contact would be very expensive because of the need to clear lineside structures, including bridge girders and platforms, to provide more space for the conductor rail and shoegear. This option would offer only winterisation benefits. Conversion to any form of overhead electrification would offer significant additional benefits in the form of reduced track maintenance and renewal costs, some improvement in energy efficiency and a reduction in the risk of electrocution. However the energy efficiency improvement delivered by 25kV overhead electrification is very much higher than the other options. It is in the order of 20% at the supply point. This represents a very large potential gain to the industry. Of equal importance to the energy efficiency gain is the potential for the 25kV AC system to sustain the substantial increases in electrical demand which are likely to be needed to deliver additional passenger and freight capacity in the future, compared with the 3rd rail DC system which is approaching its limits in terms of ability to deliver power to high-frequency services over lengthy routes. The estimated capital costs of replacement of the 3rd rail system with 25kV AC overhead are less per track kilometre than full renewal of the 3rd rail system, even taking into account the need to provide additional clearance through bridges and tunnels. However, for operational reasons the replacement would have to be carried out on a 'line of route' basis, which may mean some DC equipment being replaced before it is life expired, so there will be some increase in costs in the short-term. Costs of signalling immunisation are relatively small. About 25% of all DC rolling stock is already dual voltage (750V/ 25kV) and a further 40% is designed for easy conversion, requiring only the addition of pantograph, transformer and controlled rectifier, set in space already provided. The balance of rolling stock will require special provision and may not be worth conversion, considering its remaining life. In most cases the older rolling stock is likely to be replaced during the envisaged conversion timescales. An outline implementation strategy and insertion plan have been developed which suggest an 'outside in' approach consistent with the patterns of use of dual voltage and readily convertible rolling stock, starting at the extremities of routes away from London and working inwards. Complete conversion of the network would take a minimum of 15 years and would need agreement of a common strategy with Transport for London, allowing for the areas of overlap with London Underground. In summary, the findings of the research project are: • Reduced cost - The costs of running a DC electrified railway are well in excess of an equivalent AC electrified railway, taking into account energy usage (including losses), maintenance and renewals. Research by Network Rail and train operators has quantified the high electrical losses associated with the 3rd rail system, particularly on relatively long distance routes. • Increased performance - 25kV AC allows the train to accelerate faster, giving an average time saved for a stopping service in the region of 3-5%. The improved performance could also be used to relieve congestion or provide better perturbation recovery. • Increased capacity - the 25kV AC system would support expected future increases in passenger demand, allowing for increased energy consumption by as much as 50%, whilst an equivalent upgrade to the current DC system would not be economic. • Technical - The DC system poses more challenges as it gets upgraded because of the thermal capacity limitations of the current equipment. These challenges can only be addressed by providing more paths for the current flow; however terminating those paths is very challenging. For main line purposes 3rd rail is a technically obsolete system. • Improved safety - Overhead distribution reduces the risk of electrocution compared with third rail. The benefits arising from replacement of the 750V DC 3rd rail system with 25kV AC overhead may also be considered from the perspective of the various stakeholders: • All parties will benefit from the reduction in sensitivity to ice and snow. • Passengers will benefit from increased system performance, which can support reduced journey times and higher route capacity. • Train operators will benefit from the reduction in energy consumption. • Network Rail will benefit from reduction in the capital costs of renewal of the electrification infrastructure, from a reduction in the cost of track maintenance and renewal, and from reduced electrical distribution charges and costs of control. • Taxpayers and passengers will benefit from reduced whole life system costs. • Society in general will benefit from the reduction in carbon emissions associated with reduced energy consumption and from the reduction in risk of electrocution of members of the public who accidentally or deliberately stray onto the track. • Additional benefits, considered too remote for evaluation in this study, include energy and operational cost savings from electric operation of freight and cross-country passenger services, and greater flexibility in cascading rolling stock
