Tuesday, February 1, 2011

Signalling Case Study - Paris RER A

Paris Metro Line 14
Now that Cross River Rail has been delayed, one of the options for increasing rail network capacity is improved signalling. However, as this would involve the Government spending some money, BrizCommuter is rather pessimistic that this would happen! Anyway, here is a case study where improved signalling has significantly increased rail capacity.

Paris RER A opened in 1969 as a cross city suburban rail system. It was an instant success, and quickly became overcrowded. The fixed block signalling system could manage a maximum of 24 trains per hour (tph) per direction (every 2 minutes 30 seconds). 24tph is roughly the maximum capacity of Brisbane's suburban tracks, although BrizCommuter would expect that more than around 20tph would be difficult to achieve with current infrastructure. The solution was for RATP and SNCF to commission a signalling system on the core section of RER A, which could allow for a shorter platform re-occupation time - time from the departure of a train to the arrival of following train. This system was called SACEM, and is an in-cab signal signalling allowing for shorter overlapping signal blocks around the stations to allow for higher capacity. SACEM was jointly developed by three European companies, and the "distance to go" automated train control (ATC/ATO) version has since been installed on Hong Kong MTR. The SACEM installation on Paris RER A allows trains to run at a timetabled 30tph (every 2 minutes) in the peaks with 224m long trains - that's 80m longer than a 6-car unit in Brisbane. RER A now carries more than 55,000 passengers per direction, per hour at any point on the core section. All stations have a train service at least every 10 minutes in the peaks, and with the exception of 2 stations, all are served every 10 minutes off-peak as well. More than 1.2 million passengers are carried on RER A each day!

More recently Paris RER has had it's single deck fleet of trains partially replaced by double deck MI2N trains. This cannot be done in Brisbane due to Queensland's restrictive loading gauge. Unlike Sydney's double deckers, these the MI2Ns have 3 sets of door per car side in an attempt to reduce station dwell time.  Certainly Brisbane will require more sets of doors on car sides in the future. Also, in a bid to keep trains moving, a horn sounds at stations when the dwell time has reached 50 seconds. This prompts an immediate attempt to dispatch the train as soon as possible.

Paris RER A's high capacity is also aided by good infrastructure. There are multiple reversing points, with all termini having at least 2 platforms and/or sidings for reversing trains. Intermediate reversing points all have a 3rd track so that trains can reverse without blocking the main running lines which unfortunately occurs at Manly and Mitchelton on Brisbane's  rail system. As RER A has 2 branches at one end, and 3 at the other, grade separated junctions allow for reliable operations. This is in contrast to Brisbane's many at grade junctions, such as at Roma Street (trains entering and exiting service), and Park Road where conflicting train movements can decrease track capacity and reliability.

Showing how forward thinking France is in terms of public transport, RER A's improved signalling and higher capacity trains were not the only solution to overcrowding. Metro Line 14 (photographed), a driverless metro line which opened in 1998 was designed to partly relieve pressure from RER A. A future extension of RER E will take over, and extend one of RER A's western branches.

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