Monday, April 13, 2009

Quantifying the benefits of transit improvements

A recent research monograph featuring the Perth-Mandurah railway provides some useful ways to quantify the benefits of public transport infrastructure and service improvements.

Spacial Network Analysis of Multimodal Transport Systems: Developing a Strategic Planning Tool to Assess the Congruence of Movement and Urban Structure from Dr Jan Sheurer and A/Prof Carey Curtis has a long title and is an even longer read. While heavy going for the general reader, the effort spent on it will be well rewarded, with a method and insights applicable everywhere.

Examples of analysis techniques from the paper include:

* The concept of impediment values for movement between centres. Fast and frequent train services have the lowest impediment values while slow and less frequent bus routes have the highest
* A network analysis based on service frequency between suburban nodes, considering transfers only where services are every 15 minutes or better.
* A measure of relative public transport accessibility from various suburban centres (based on population reachable within 30 minutes travel time)
* 'Degree Centrality' or the average number of transfers required to reach other areas

A few practical messages from the paper:

* 'The network effect' where improving transport serving one area (in this case southern suburbs and Mandurah) benefits access across the entire network, not just the area in which the line is built
* New lines can speed travel, not only for CBD trips, but also, if operated in conjunction with improved buses (as happened in Perth), for cross-suburban trips as well.
* The importance of locating major trip generators next to (not 1-2km from) railway stations. The number of people within a 30 minute contour is 376 000 at Murdoch Station compared to only 177 000 at Murdoch University. Similarly Joondalup Station is accessible to 164 000 people, versus just 28 000 for the Joondalup campus of Edith Cowan University (both universities are just outside the respective station's pedshed). For Melbourne this method shows (i) how poorly accessible the proposed Craigieburn Town Centre (also just outside a station's pedshed) will likely be compared to the station itself and (ii) the benefits of a station at Southland Shopping Centre.

Sheurer and Curtis have produced an excellent paper of significant practical use. Leave your thoughts on it as a comment below.

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