Mode Split, Energy Use, and Job Location

Ever wondered if the presence of rail has much of an effect on mode choice? Yes, I'm sure it keeps you up at night too. Well, wonder no more, I think the following graph is pretty convincing that rail does have an effect:



(If you want to view this in Google Earth yourself, go here for instructions.)

The scale is hard to read, but basically the colour scale is linear, between 0% and 100% (blue to red), with deep blue being 0% of work trips by car, and deep red in areas where 100% of work trips are by car. The base data is from the 2001 Census (ABS).

Of course there is a lot more going on here. Household type varies with proximity to rail stations (in particular, there are fewer households with kids), so the above graph actually overstates the effect of the rail network, but even if you crunch the stats, you get a strong independent effect.

Another important consideration is where jobs are located. Sydney has a strong CBD, in that there are a large number of jobs in and around the CBD, and so a radial rail network provides reasonably competitive access to a large number of jobs. Job decentralisation, which some argue for, on the basis that it will reduce commute length (and energy use), is unlikely to be effective, for the following reasons

1. Any decentralized job is much more likely to be driven to, because parking will be available, and public transport will be less competitive
2. While trip length would decrease, it is easy to overestimate the size of this effect. There is plenty of evidence to suggest that substantial 'excess commuting' would continue. For more specialized jobs, decentralizing may well increase commute length, as workers are not substitutable in such cases.
3. It ignores economics. Firms locate in, or close to, the CBD for good economic reasons (access to large labour pool. agglomeration economies, etc). Trying to force jobs elsewhere (through planning) will likely impose a cost on those firms who are forced to relocate to a less desirable location.
   

FYI, the following graph shows the commute energy required for each job in the Sydney CBD. That is, it shows, for each zone, the mean number of MJ of transport energy required for workers to get to jobs in that zone. From 2001 ABS Journey to Work data. Energy is in MJ/worker of primary energy (i.e. energy in the ground).

How to view this in Google Earth at home

You need to save the following KML into a plain text file (Notepad will work), save it as whateveryoulike.kml, and then drag and drop this kml file into Google Earth:


<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0">
<GroundOverlay>
<description>NONE</description>
<name>JTW_CARONLY_PCTbr.png</name>
<visibility>1</visibility>
<Icon>
<href>http://peter.rickwood.googlepages.com/JTW_CARONLY_PCTbr.png</href>
</Icon>
<LatLonBox id="JTW_CARONLY_PCTbr.png">
<north>-33.54141728667299</north>
<south>-34.10141604662701</south>
<east>151.3614161776215</east>
<west>150.65141715537854</west>
<rotation>0</rotation>
</LatLonBox>
</GroundOverlay>
</kml>