Speeding up commuter rail services without providing excess capacity

With increasing passenger numbers using the commuter rail networks in Australia’s major cities, a great deal of attention has been aimed at providing upgraded and new infrastructure to cope with the increasing stress on the networks – particularly in Melbourne and Sydney.

In many cases the new infrastructure is necessary and the investment is well justified. But in many cases all the new investment does is exacerbate an existing problem elsewhere on the network, or create a lot of spare capacity in the process. This is certainly true of the rail networks in Australia’s metropolitan areas.

Think of your typical suburban railway corridor that runs through most Australian cities – two tracks, one serving trains travelling in each direction. Most lines that fit this description are in Melbourne, but can be found in every one of Australia’s five major cities. Some of these lines are very long and become very crowded near the city end of the line during peak hours.

No one wants to be sitting on a crowded train from the city to reach their outer suburban terminus destination that stops at every station along the way. But with only one track serving trains in each direction, how else can the services be run?

Many of these longer lines in Australia run a mix of slower and faster services. However, with limitations posed by having only two tracks there is a tradeoff between the speed of the services and the frequency of the services provided. More faster services means a larger required gap between services to prevent faster services becoming stuck behind slower services – as there is no way for services to overtake each other.

A typical solution used to allow for more services and express services to overtake slow all station services has been to upgrade corridors to three or four tracks and dedicating one or more tracks to the express services. The four track setup with a slow and fast track in each direction can be found on the East Hills Line in Sydney between Wolli Creek and Kingsgrove. The less common three track setup is found on the Belgrave and Lilydale Line corridor between Burnley and Box Hill in Melbourne, with one track serving trains in a certain direction according to time of day.

The four track setup used on the East Hills Line in Sydney (left), and the three track setup used on the Lilydale Line in Melbourne (right).

While the above solutions certainly allow express trains to overtake slower trains on the longer lines, is building long sections of duplication of existing track necessarily the best way to deal with this issue? In the East Hills Line situation, where the line was converted from two tracks to four at the turn of the millennium, the capacity of the corridor is effectively doubled. Suddenly, there’s a whole lot of spare capacity on the network while junctions further along the corridor at Glenfield and Wolli Creek continue to restrict it! By international standards, almost none of Australia’s commuter rail lines run what can be classified as “frequent services” which is a train at least once every 10 minutes during the day. Even in Australia’s largest city, the trains certainly don’t run that frequently.

So how else can commuter rail services be sped up without providing long sections of duplicated line that can require large numbers of compulsory property acquisitions, new bridges and tunnels, rail and other associated electrical and civil works? My inspiration comes from how the Japanese run their trains. The western rail corridor between Redfern and Strathfield out of Sydney has six tracks and carries over half a million people daily. The Hanwa Line out of Tennoji terminal in Osaka’s southern suburbs moves almost as many people with only two tracks, runs trains every few minutes all day long and still runs a variety of faster and slower services. How?

Efficient track layout and infrastructure usage.

Traditionally, passing loops have been used on the long distance freight lines operated by the ARTC to allow trains to pass trains travelling in the opposite direction. But in Japan, they are sometimes used to allow trains travelling in the same direction to pass other services. And the location that this is technique is most often implemented is at stations.

An example of a passing loop used at a suburban train station.

There’s a number of additional benefits from operating services in this manner other than allowing for a mix of fast and slow services. It makes for much more efficient use of the existing infrastructure. It also allows cross platform interchange for passengers to transfer between faster and slower services. This gives opportunities for passengers travelling to and from minor stations served by only slow services to change to a faster service at a major station (where the passing loops could be installed) instead of wasting time on a slow service for the entire trip. It also reduces the potential disruption that would otherwise occur for a track duplication.

One place where this could be implemented is along Adelaide’s Gawler and (newly extended) Seaford Lines. These two lines are Adelaide’s longest and busiest rail corridors, with many stations and a variety of train services. With proposed peak hour frequencies as often as every 7 minutes during peak hour on the Seaford Line when it is commissioned, and more frequently between Ascot Park and Goodwood where the tracks are shared with the Tonsley Line, something will need to be done to the rail corridor to make this frequency sustainable. And with the corridor hemmed in by homes for much of its length, I believe that implementing passing loops at a number of stations will help the situation.

Is this passing loop solution always better than the duplication alternative? Absolutely not. By allowing trains to run more often on existing tracks, there is the potential to create long delays at railway crossings and there are still capacity restrictions posed by having only two tracks. To make it work properly, the trains have to run on schedule otherwise any delays will create knock-on delays across other sections of the network. Running longer trains or duplicating corridors can still be better choices than implementing passing loops.

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2 Responses to “Speeding up commuter rail services without providing excess capacity”

  1. chris Says:

    This is very interesting thanks. Being a train illiterate, I can only wonder if the Australian system could cope with suburban passenger train passing loops, and suspect it might be a bridge too far…see for example here:
    http://www.atsb.gov.au/publications/investigation_reports/2006/rair/rair2006003.aspx

    • Andrew Says:

      Hi Chris,

      Yes, the signal system would definitely be something that would need to be attended to in implementing passing loops on the suburban system. As I understand, the SA government is currently investing in an upgraded signal system which communicates with the trains and can automatically bring the trains to a stop if a “signal passed at danger” or SPAD occurs.

      I don’t know much about these sorts of electrical systems. It definitely is workable from what I have seen elsewhere though.

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