Sunday, November 11, 2012

Mapping public transport accessibility in Sydney

Back in November last year, I blogged here about the first Sydney Alliance Transport Assembly, where we launched our campaign for improvements to public transport in Sydney.

It's not surprising that transport is one of the issues that the 52 partner organisations of the Sydney Alliance have chosen to work on together. Being able to get around is so fundamental to just about every aspect of urban life.

Our vision for an integrated and effective transport network focuses on addressing the key accessibility gaps with the following standards:
400  (everyone should be within 400 metres of public transport)
15 (that transport should come at least every fifteen minutes throughout the day)
1 (you should only need to pay once for any journey, no matter how many transfers you make)
S (you should feel safe)
C (it oughta be clean)
A (it oughta be accessible to all, regardless of who you are)
A (it should be affordable)

Since that Assembly, the Alliance's Transport Research Action Team has been very busy working on the 'S' in the formula, to take some first steps on the path to making this formula a reality. We've negotiated with councils to improve lighting in council car parks in several suburbs. We're also building a campaign on night-time staffing of key interchange train stations around the city.

Meanwhile, as part of the preparation for our work in 2013, Laurence Troy and I (both members of the National Tertiary Education Union) have been working together with members of the Sydney Alliance Transport Research Action Team to map the city on the '400' and '15' elements of the formula.

The map on the left shows which bits of Sydney have access to some form of public transport within 400 metres walk. The map on the right shows which bits of Sydney have access to some form of public transport within 400 metres that comes at least every 15 minutes during the day. As you can see, there's a lot less purple in that second map.

This weekend, an article based on the maps was published in the Sun Herald with some follow up stories on ABC Radio and Channel 7 news Today Amanda Tattersall (Sydney Alliance Coalition Director) has an opinion piece published in the Sydney Morning Herald.

You can also interact with the maps on the Herald website, which has produced an interactive version on a Google Map layer.

Big props to Laurence Troy, for his fantastic mapping skills. And also to all my fellow Transport Research Action Team members ... yay team!

Anyways, just in case anyone is interested in a little more detail about how and why the maps were made, here's a bit of an 'FAQ' ...


How did we make the maps?

Laurence Troy and I made the maps above using Geographic Information Software networking tools. Using this software, we combined three key kinds of digital information: the road network; public transport service points (train stations, bus, ferry and light rail stops), and; average frequencies of services at each point between 5am and midnight on a weekday. We then generated a map that shows which parts of the city are within 400 metres walking distance of a public transport service point, where a service comes at least every fifteen minutes on average across the day.
The road network data we initially used was provided by the NSW Department of Lands. The data about public transport service points and frequencies was provided by the Transport Data Exchange Program. The web maps produced by The Sydney Morning Herald for their feature have overlayed our shape files onto a Google map.

Why did we make the maps?

The map was produced as part of our work in the Sydney Alliance's Transport Research-Action Team. Based on our research into successful public transport systems around the world, we believe that the minimum walking distance to make door-to-door public transport a reality for Sydney-siders is 400 metres. The minimum service frequency to help make public transport a viable alternative to the car is 15 minutes. 
Of course, distance and frequency are not the only factors that influence the accessibility and quality of public transport. Other factors are important, such as integrated and affordable ticketing across all modes of public transport, safety, the physical accessibility of transport infrastructure, and the quality of public transport environments. These factors are combined in the Alliance's formula for public transport in Sydney: 400:15:1 SCA2. To find out more about this formula, visit:

What do the maps tell us?

The maps identifying gaps in the existing network at the metropolitan and neighbourhood scale. Plugging up these gaps should be prioritised in public transport planning in the years to come. In particular, we will be using these maps in our work to show how existing transport resources and infrastructure could be re-organised to improve service coverage and frequency. The maps could also help to inform decisions about the provision and prioritisation of expensive new infrastructure.
The map calculates distance to public transport as walking distance along the road, not 'as the crow flies', because as we all know, we often have to walk around houses buildings and other objects to get to a bus or train stop.
The map is not focused only on peak hour frequencies, but on frequencies across the entire day. That's important, because most of our travel is not commuting to work. In 2009-10, commuting accounted for 28% of the distance we travel and 16% of the trips we take in the city (source: NSW Bureau of Transport Statistics). And of course, even some of that commuting takes place outside peak hours for shift workers, hospitality workers, etc.

What are the limitations of the maps?

The method for calculating frequency of service has some limitations, and actually makes service frequencies look better than they are in some places. For each service point, we have calculated average frequencies from 5am to midnight by dividing those 1140 minutes by the total number of services that stop at that point. But an average frequency of 10 minutes at a bus stop might be achieved by 3 different bus routes stopping at that stop twice per hour. If you are dependent on one of those bus routes for your travel, your actual service frequency is 30 minutes, not 10 minutes.
The method for calculating walking distance also has some limitations, which might make the area accessible to public transport look smaller or larger than it actually is. This is because for most of the city, we are using the road network to calculate walking distance. However, in some places pedestrians can use footpaths that offer short cuts, and right now we do not have most of those paths on our map. In other places, pedestrians may not be able to walk along roads.
When the software is matching bus/train/ferry stop locations with the nearest bit of road, it searches within 50 metres around the stop.  Sometimes a bit of road might be 60 metres across some grass, which pedestrians can walk across, but our system hasn’t recognised this. 

Help us improve the map

There road network and the transport network are very large, and trying to model accessibility for the whole metropolitan area is a big job.  We use Geographic Information Software to automate the process which sometimes creates errors and checking every single bus and train stop for its accuracy is not possible.  We are continuing to develop our understanding of the geography of public transport over the coming months. If you find any errors or anomalies in a part of the city you know well, get in touch and let us know!


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