Can activity centres supply enough housing?

Average annual growth in population of centres (%) - data from BITRE

Melbourne 2030 envisaged growth of high density housing and office employment within established suburbs would be located in activity centres, especially those with a rail station. In fact it specified that 41% of all dwellings should be constructed in activity centres over the period 2001-30 (with 31% in Growth Areas and the rest dispersed in small projects throughout established suburbs – at present though, about half of all new dwellings are constructed on the fringe).

Locating more intensive development within strategically important activity centres makes a lot of sense. In particular, it means a larger number of people will be within walking distance of frequent public transport, giving them an alternative to driving. Bigger activity centres should be more sustainable and might even cost the public sector less in infrastructure outlays and operating costs.

Yet it doesn’t seem to be happening – outside of the city centre, only a small number of activity centres are experiencing significant growth in multi-unit housing. Moreover, according to research by BITRE, Melbourne’s six Central Activities Areas (CAAs) and 25 Principal Activity Centres (PAC) only accounted for 3.6% of all population growth in the metropolitan area between 2001 and 2006. The number of people living in CAAs fell (by -0.3% p.a.) over the period and the number in PACs grew by just 0.8% p.a. – much lower than the growth rate for the metro area and the CBD (see exhibit).

Nor are activity centres generally successful in attracting employment – BITRE found jobs growth was actually negative in the CAAs, falling by 0.5% p.a. between 2001 and 2006. Jobs grew by 1.25% p.a. in dispersed areas outside of centres over the same period, but by only 0.5% p.a. in PACs.

There are reasons why it’s hard to attract developers to larger centres. Assembling land is difficult – existing holdings are in diverse ownership, values are often high and lots may be small. Moreover, Planning restrictions mean suitable sites are in short supply or have constrained redevelopment potential. But perhaps the key issue is opposition to development from existing residents.

As the strong reaction to Banyule Council’s proposed structure plan for Ivanhoe shopping centre shows, many residents don’t like the idea of redevelopment at up to 4-8 storeys in their local centre. They fear higher housing and employment densities will increase traffic congestion and noise and they expect the character and familiarity of their local centre will change for the worse. They see few, if any, upsides for them personally from a higher density centre.

It seems putting most higher density redevelopment eggs in the activity centres basket isn’t paying off. The politics of dealing with existing residents is simply too hard for all levels of government, whatever their colour. That’s not surprising given residents generally feel redevelopment makes them worse off and the planning system emphasises the interests of local residents.

Economists like Edward Glaeser and Ryan Avent have proposed ways that in theory might give existing residents an incentive to be more accepting of redevelopment, e.g. residents could buy the right to remain living at low density. These are novel and interesting ideas but at the present time they’re simply not going to fly politically.

Any redevelopment within established suburbs is going to be difficult. However the level of opposition can be reduced, although by no means avoided, where more intensive development is proposed for disused industrial areas. Even so, “brownfield” sites come with their own set of issues, like potential contamination and possible alternative uses.

Further, there don’t actually appear to be many brownfield sites. The authors of Challenge Melbourne – the discussion paper prepared in 2001 as part of the Melbourne 2030 process – estimated suitable brownfield sites within established suburbs have a total potential yield of 65,000 dwellings. That’s impressive, but even if all of that estimate could be realised, it’s not a big enough contribution, given the number of households in Melbourne is now projected to grow by 825,000 between 2006 and 2036. Read the rest of this entry »


What’s happening with suburban jobs in Melbourne?

Density of employment in Melbourne, 2006, in one km wide circular bands by distance from CBD (jobs/km2)

The first exhibit shows the popular view of the geography of urban employment in Australia’s largest cities. It is commonly assumed the great bulk of jobs – and certainly virtually all “good” jobs – is located in the CBD.

This is an understandable view given the first exhibit shows the spatial distribution of employment density in Melbourne in 2006. It indicates the density of jobs in the Central Business District (CBD) – the first one km radius ring around the town hall – is an order of magnitude higher than anywhere else in the metropolitan area. It closely aligns with the cluster of high rise office buildings that define the CBD in the popular imagination.

Share of metropolitan employment in Melbourne in one km wide circular bands by distance from CBD, 2006 (%)

But is this is an adequate representation of the geography of employment in Australia’s second largest city? The second exhibit highlights that density is not the same as the number of jobs. It shows how employment is really distributed within Melbourne – the CBD is easily the largest single concentration of employment, but it nevertheless has only 15% of all metropolitan jobs. In fact only 28% of metropolitan jobs are located in the inner city – i.e. lie within a 5 km radius of the town hall – and 50% are located within 13 km radius.

This dispersed pattern is not recent. Melbourne was compact and dense up until the end of the nineteenth century when the appearance of mechanised transport – primarily trams and trains – enabled middle class residents to escape the crowding and congestion of the centre for the space and amenity of the suburbs. This trend was boosted dramatically after WW2 when increasingly widespread car ownership democratised access to affordable land on the urban fringe.

Firms followed a similar pattern. Initially, manufacturing and distribution firms moved to the outer suburbs so they could escape congestion in the inner city, exploit new space-intensive horizontal production methods, and be closer to the suburbanising workforce. The suburban population generated increasing numbers of jobs to service its consumption needs, amplified by the increasing level of outsourcing from the home. More recently, some higher order activities have moved from the CBD to near-CBD and inner city locations and some back office functions have moved to the suburbs.

By 1981, only 35% of Melbourne’s jobs were located within 5 km of the centre. The “average job” was 12.4 km from the centre and the “centre of mass” of employment was 5.9 km away. The trend to the suburbs was very strong over the succeeding 25 years. By 2006 just 28% of jobs were within 5 km radius and the ‘average job’ was now 15.6 km from the centre. The centre of mass had moved 2 km further outwards to the vicinity of Tooronga, 7.9 km from the CBD. Read the rest of this entry »


Do trams provide better accessiblity than trains?

% of metropolitan households and jobs within 400 m of a tram/train/SmartBus stop (data from DoT)

New research by the Victorian Department of Transport (DoT) shows Melbourne’s tram system provides access to 34% of metropolitan jobs, whereas trains only give access to 15% (see first exhibit). The analysis found trams also give better access to housing – 17% of metropolitan households are located close to a tram stop compared to 8% close to a train station.

DoT calculated the proportion of metropolitan jobs and households located within 400 metres of tram, train and SmartBus stops, using 2006 Census data.

The superior accessibility of trams might seem surprising given most popular discussion about public transport is focussed on trains. Moreover, trams and trains both serve the employment-rich CBD, so the difference in access to jobs is probably higher than most expect.

The department doesn’t offer an explanation, however there are logical reasons for the superior showing of trams. These include the higher density of the tram route network, the greater frequency of stops, and the relatively high employment and housing densities in the central part of the metropolitan area served by the tram network (i.e. the inner city and inner suburbs).

In the inner eastern suburbs, for example, there are nine parallel east-west tram lines between Victoria Rd and Glenhuntly Rd, a distance of just 8 km. The tram line on High St in Prahran is paralleled by another route just 560 metres to the north on Malvern Rd and one 650 metres to the south on Dandenong Rd.

As shown in the second exhibit (under the fold), tram stops are much more closely spaced than train stations. Tram stops in the inner eastern suburbs are every 200-300 metres, whereas stations in this area are usually more than a kilometre apart.

The tram network also services an area of high job density. The inner city – the area within 5 km of Melbourne Town Hall – might only have 28% of all metropolitan jobs, but they are concentrated in a relatively small area. Likewise, 50% of all jobs in Melbourne are more than 13 km from the centre, but the 0-13 km half is necessarily at much higher density than the 14+ km half.

Compared to the tram system, the train network is relatively sparse, particularly in the middle and outer suburbs where not only the distance between the radial lines increases as a function of simple geometry, but the distance between stations also increases. The distance from Narre Warren station to Berwick station, for example, is over 4 km – the 400 metre walk radius assumed by DoT accordingly misses much more than it picks up.

Suburban rail lines don’t in any event tend to be near jobs. As I’ve pointed out before, the vast bulk of suburban jobs aren’t located within large centres, but instead are relatively dispersed. Even the minority of jobs that is located in large centres tends to be spread out over a relatively extended area rather than concentrated within a small and neat 400 metre radius.

Clayton is by far the largest concentration of jobs within Melbourne’s suburbs, yet very few of the jobs it contains are near a rail station. The second largest job concentration in the suburbs is Tullamarine, which isn’t served by rail at all. The high proportion of jobs accessible by SmartBus services signals clearly that most suburban jobs aren’t within 400 metres of a rail station.

But providing potential access to lots of jobs is not the same as actually delivering workers to them. Trams might be within 400 metres of twice as many jobs as trains, but the latter nevertheless carry well over twice as many commuters to work each day as trams. There are a number of reasons for this difference.

One is that the assumed 400 metre walk distance is harsh on rail. Commuters are prepared to walk further to their nearest stop if the overall journey is long. As rail work trips are on average much longer than tram trips, the assumed walk distance to a station is too restrictive – a distance of 800-1,000 metres would be more reasonable.

Another reason is that many more train travellers get to their train station by other motorised modes – principally by car, but also by bus and tram – than is the case for trams. In fact half as many train travellers combine motorised modes as simply take the train direct. In contrast, the number of workers who use another motorised mode to connect with a tram as their main mode is quite small.

Probably most importantly, taking a tram to work is slow. Trams stop frequently and, because they don’t have their own right of way for much of the route, get caught in peak hour traffic. Commuters who have a choice will take the train instead, either driving to the station or using a bus or tram to connect. Another factor is that many inner city and inner suburban workers are on high incomes – rather than take a slow tram, some will get a car and/or a parking space as part of their remuneration package and will elect to drive instead.  Read the rest of this entry »


Where is Melbourne’s ‘centre of gravity’ ?

Change in the 'centre of mass' of employment in Melbourne, 1981-2006

We’re familiar enough with the idea of the ‘centre of gravity’ of population in Melbourne. But where is the centre of gravity of employment?

Is it the city centre? No, for one thing the CBD’s only got around 15% of all metropolitan jobs. For another, the combination of Melbourne’s distinctly lop-sided growth south of the Yarra and the fact that 72% of jobs are more than 5 km from the CBD, suggests it’s going to be somewhere south east of the CBD.

So I’ve calculated the location of the centre of gravity (more correctly, the ‘centre of mass’) of jobs from Census data. The accompanying chart shows how that location changed over the period from 1981 to 2006.

The centre of gravity is calculated by dividing Melbourne up into 1,000 traffic zones and weighting the coordinates of the centroid of each zone by the number of jobs it holds. If you imagine a relief model of employment in Melbourne, the centre of gravity is where you’d rest the model on a needle so that it balancess perfectly.

In 1981, the centre of mass of employment was 5.9 km east south east of the CBD, on Kooyong Rd, just north of Toorak Rd. By 2006 it was 7.9 km from the CBD, close to the corner of Malvern and Tooronga Rds.

This movement reflected the much stronger growth in jobs in the suburbs over this period compared to the CBD and inner city. Read the rest of this entry »


Is this a sensible comparison of cars and public transport?

Many readers will have seen this now-ubiquitous chart before – it’s from Melbourne 2030 and has been republished countless times. It shows the proportion of metropolitan jobs accessible within 40 minutes travelling time from different parts of Melbourne by car and by public transport.

I’ve never been happy with this chart because its simplicity is deceptive – I don’t accept the implicit premise that public transport should be judged on the same basis as cars. I’ll come to that shortly, but first there are some technical shortcomings that need to be addressed.

One is that the chart doesn’t say how the data range intervals are determined – are they equal counts? Are they based on a ‘natural break’ in the way the data is distributed? It’s not possible to be confident that they portray the situation with either public transport or cars in as objective a way as possible.

Another shortcoming is that a mere three categories is very limiting. If you live in Sunbury (say), the chart says you can drive to between 3% and 25% of metropolitan jobs within 40 minutes. That’s an enormous range – a factor of more than eight between the lowest and highest values. It’s essentially a useless piece of information. And the maps give a misleading impression of how many Melburnians live in areas with the poorest accessibility. There are very large areas on the fringe that have a tiny population e.g. there is a 9 km wide greenbelt between Melton and Caroline Springs. Much of the outer north east is a catchment area.

Yet even with these technical flaws, there is some intriguing information. For example, the majority of the population can access no more than 2% of metropolitan jobs within 40 minutes travel by public transport. Read the rest of this entry »


Does density matter for mode share?

Mode share vs density (click to enlarge)

The accompanying chart shows how public transport’s share of the journey to work varies with population density across 41 US and Australian cities.

It is taken from the same article that I mentioned in my last post. The authors, Dr John Stone and Dr Paul Mees, find there is only a modest relationship between population density and transit share (R2 = 0.229). They conclude that “higher density across the whole urban region is not the explanatory variable that many might expect”.

Los Angeles, for example, is the densest metropolitan area in the US – denser ever than New York – yet the chart shows public transport’s share of work travel in LA is much smaller than in NY.

If that seems counter-intuitive, your intuition could be right. The chart uses average population density calculated across the entire urbanised area of each city.

While that’s perfectly alright in some contexts, it doesn’t allow for the possibility that public transport’s ability to win travel away from cars is related to the morphology of density – the ‘peaks and troughs’ in the way the population is spatially distributed. It’s possible that the relative proportion of population in high density areas vs low density areas has a greater impact on mode share.

Using average density probably won’t present a serious problem with cities like Atlanta, Austin, Dallas, Phoenix and Portland where the population is overwhelmingly suburbanised at relatively uniform (low) densities. But it could have a big impact on places like New York which have an extensive ring of low density suburbs as well as a high density central region e.g. Manhattan and Brooklyn.

A way of dealing with this issue is to use weighted density rather than average density. This involves weighting the density of each suburb (or other convenient geographical unit e.g. traffic zone) by its share of the city’s total population. So a one km2 suburb with 5,000 residents (say) carries a lot more weight than another suburb of the same area that has only 1,000 residents. Read the rest of this entry »


What is the inner city?

We all use the term “inner city” but I doubt we’re all talking about the same geographical area.

For some people, the inner city means the area where cafe society thrives – probably a 10 km circle around the CBD in cities like Sydney and Melbourne. Or it might mean the extent of medium density historic terrace housing.

Some Brisbanites think of the inner city as the large area covered by the Brisbane City Council (1,367 km2) while some Melburnians think of it as the area serviced by tram lines.

Planners have addressed this problem by adopting simple measures. For example, in Melbourne the inner city is customarily defined as the area covered by the central municipalities of Melbourne, Yarra and Port Phillip (77 km2). Sometimes the Prahran portion (SLA) of the City of Stonnington is also included.

In my work on Melbourne I define the inner city as the area (79 km2) within a 5 km radius of the City Hall . This approximates closely to the three inner municipalities, but I use it because it’s consistent with what’s done elsewhere. US researchers typically use a 3 mile radius to define the inner city – an area approximating the size of the central Counties of the larger metros.

There are a number of problems with this sort of ‘administrative’ approach. A key one is that there is no underlying rationale for where the boundary is drawn – why not 2 km or 10 km? Another is that it doesn’t really connect with people because it has no obvious reference like, say, the tram network. Read the rest of this entry »