Is public transport ‘CBD dependent’?

Journey to work mode share, Sydney

A recent paper on travel in Sydney illustrates how dependent the CBD is on public transport and, in turn, how dependent public transport is on CBD commuting.

The paper analyses the journey to work in Sydney using data from the 2006 Census. It was undertaken by Blake Xu and Frank Milthorpe of the NSW Bureau of Transport Statistics.

Although the great majority of travel in Australia’s capitals is now undertaken for non-work purposes and is dominated by the car, the journey to work nevertheless remains an important travel purpose.
This is partly because it generates the largest peak in demand and partly because it is the one travel purpose where public transport’s mode share still remains relatively high.

The first chart shows that, as is the case with other capitals, public transport dominates commutes to the CBD in Sydney. It captures 75% of all journeys by Sydney CBD workers, whereas the car only gets 20%. That’s a bit higher than the other capitals but it’s an expected result.

Journey to work, market share by mode, Sydney

However what might surprise is that outside the CBD, public transport’s share is quite small. Only 13% of people who work elsewhere in metropolitan Sydney use public transport to get to work, while 80% drive.

When the CBD and the rest of the metropolitan area are taken together, the mode split for commuting for all of Sydney is 22% for public transport and 71% for car. Despite its high public transport share, the CBD has a small effect on the Sydney-wide average because it only has a small proportion of all jobs in Sydney – it accounts for just 14% of total work journeys.

Public transport patronage grew strongly in Sydney in absolute terms over 1981-06, but car use grew even faster. Transit’s share of work journeys fell from 25% to 22% over the period.

These numbers tell us that public transport is extremely important for the functioning of the CBD. Delivering large numbers of workers to the Sydney CBD in peak hour simply wouldn’t be possible without it.

But they also tell us that the CBD is just as important for public transport. In fact the second chart shows that work journeys to the CBD by train, bus and ferry comprise nearly half (47%) of all journeys to work by public transport (in comparison, work trips to the CBD by car comprise only 4% of all car commutes in Sydney).

That’s a startlingly high figure when it’s considered that those public transport CBD journeys account for just 10% of all work journeys in Sydney. So not only is public transport very dependent on a minority trip purpose (i.e. work journeys), it is heavily reliant on just a small portion of those work journeys.

This emphasises a point I’ve made a number of times before that concentration of activities – especially employment – is a key determinant of whether or not public transport wins a high mode share in Australia’s major cities.

Too much attention is given to increasing residential density in order to increase public transport’s mode share. There are other reasons to promote increased residential density – primarily to enable more people to live in central locations – but mode share isn’t the prime one.

Where the objective of policy is to increase public transport’s share of travel at the expense of cars, the primary focus of land use policy should instead be on concentrating activities spatially, particularly jobs. That strategy will create conditions conducive to transit and unsympathetic to cars.

9 Comments on “Is public transport ‘CBD dependent’?”

  1. Joseph says:

    You make a number of interesting points but I believe you end up reaching an unsupportable conclusion. If I can paraphrase your argument it is that concentrating activities create congestion meaning people will have to use public transport. Creating congestion is a very odd aim of public policy, you could achieve it quite easily by turning off all the traffic lights, but it wouldn’t make it a good idea.

    Where the logic falls down is in assuming that increasing public transport share at the expense of cars is an end in itself. If the objective instead was the perhaps more worthy goal of trying to reduce the amount of time spent travelling then it is apparent that policy should be focussed on reducing congestion.

    • Alan Davies says:

      Firms concentrate in a small area like the CBD to obtain agglomeration economies. An inevitable by-product of concentration is congestion. Public transport is accordingly necessary to deliver workers on the scale required by CBD businesses.

      Congestion is a bad thing but public transport won’t by itself do anything to reduce it. What’s needed are other mechanisms like road pricing, which will give some drivers an incentive to change their behaviour. One of those potential changes is shifting to public transport.

    • Michael (another Michael) says:

      “Where the logic falls down is in assuming that increasing public transport share at the expense of cars is an end in itself.”

      Increasing cycling, walking and public transport at the expense of car travel is an end in itself unless you are wilfully ignorant about global warming and blind to all the externalities cars create. Naturally if you are a motorist then you probably find it easy to put these externalities out of your mind.

      • Joseph says:

        As far as global warming is concerned the objective of public policy should be reducing GHG emissions at lowest cost. Dramatic improvements should and could be made in power generation before needing to go anywhere near transport. Confused thinking on this leads to expensive and ineffectual policies such as subsidising rooftop solar panels and results in others demanding public transport for climate change reasons without demonstrating why this is cost effective.
        There are indeed other externalities with cars although I believe they are frequently blown out of proportion. Safety is the main one and unfortunately doesn’t get the priority it deserves.

      • Alan Davies says:

        Joseph, as you probably know, I generally agree with your position (e.g. see here, here and here). However CBD work travel is one market where public transport is the lowest cost solution and the most efficient.

  2. rohan says:

    be interesting to see similar graphs for other places in sydney with significant job concentration, or at least lots of office towers, like chatswood and parammatta – we dont have anything like those mini-cbds in Melbourne, but I think they are what is envisaged for dandenong, broadmeadows, ringwood – though I cant see any of them ever ending up like chatswood….

    • Alan Davies says:

      The authors identify 13 major employment centres (excluding the CBD) and find that, collectively, they account for 22% of all journeys to work in Sydney taken by public transport. The aggregate mode split for these centres is 32% public transport and 65% car. The authors don’t give any info on individual centres.

  3. brisurban says:

    “Although the great majority of travel in Australia’s capitals is now undertaken for non-work purposes and is dominated by the car …”

    This is really interesting- where are all these non-work trips coming and going? What is driving them? Leisure? Shopping? Tourism?

    • Sam says:

      Judging by the drop in traffic congestion during school holidays a significant part might be the school run.

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