[train passing] ♪ background music ♪ (Narrator)
This is the Potteries Line. It’s not the busiest line in the world, but recently rail journeys have become more congested owing to higher passenger demand. It’s not possible to increase the number of services as the line is already running at its current maximum. One way to increase the capacity of the line is to reduce the overall journey time which will also increase passenger satisfaction. However, there are a number of manual level crossings on the Potteries Line, all of which incur additional signalling and block markers to stop a train if a barrier’s not closed to road traffic which increase headway distances and slow down services. Network Rail would like to investigate changing these to automatic level crossings. Improving journey times by reducing train headway and decreasing delays to road traffic waiting longer than necessary at barriers. One of the key factors in calculating the capacity of a line is headway. Headway is the minimum safe time interval between trains and is dependent on signal spacing, speed and breaking. When a train has to undergo emergency breaking the train behind it must have sufficient time and distance to stop safely. If the headway’s too big, there’s too much empty track and the route isn’t being used efficiently. But if we reduce the headway too much, then there is insufficient time for the signalling to warn the driver of a following train in the event of a sudden stop. The minimum headway for the line is used to determine where we position the railway signals. For a line with a constant speed, this is quite simple. But when we have a speed restriction, the headway becomes more difficult to calculate. A speed restriction can create “bottlenecking” as we see here. This is unacceptable on a regular, scheduled service. To avoid this the trains need to be spaced out, increasing the headway but limiting the capacity of the entire line. As we have heard, manually operated crossings incur speed restrictions and speed restrictions affect services. As you can see from this animation. At unrestricted speed, these two tracks can carry 8 trains at once. But with a restriction, journey times go up requiring more trains to run the same frequency of service reducing the efficiency of the line and increasing journey times. The answer is automation. By automating manual crossings, we can remove the speed restriction. A reduced journey time leads to higher passenger satisfaction. It reduces the number of trains required to run the service, allowing more time for maintenance. It may enable a more frequent service and reduce overcrowding. And it reduces the safety risk, by removing the human aspect of the barrier system. There are a number of crossings that we need to automate on the line. The first level crossing under consideration is a user-worked crossing used to provide access to farms, minor roads and residential properties. Users of the crossing are required to call the signaller from the adjacent phone to check there are no approaching trains. The second crossing is across the centre of a village high street. It’s adjacent to a signal box, and is operated by the signaller as required when it is safe to allow cars to cross. The third crossing is located at the end of a station with two platforms. The station serves a small town but is outside of the town centre. The crossing is operated by a member of station staff as required. We’re sending you a series of challenges to help us automate or remove the need for these crossings. It’s an important job. Remember: automation could mean a better, safer service.