Weekly cost of commuting per household by car and public transport, Melbourne (Data from BITRE)

The exhibit shows that in terms of weekly household cash outlays, commuting by public transport is vastly cheaper than commuting by car, irrespective of where the commuter lives (see first three rows).

Both fixed and variable costs are much higher for cars than for public transport. For example, outer suburban households where the workers drive spend $302 p.w. compared to $41 p.w. for households whose workers use public transport.

The real killer for cars is fixed costs such as depreciation, interest and registration. These dominate variable costs like petrol, servicing and parking.

The numbers are taken from this report (which I’ve mentioned a few times recently) by the Bureau of Infrastructure, Transport and Regional Economics (BITRE). The Bureau looked at the journey-to- work costs a household of two adults and two children aged under 18 years face in Melbourne, and how they vary by location and mode.

Location is an important variable – BITRE assumes household income, level of car ownership and commuting distance/time vary substantially by location (measured here as inner city, middle suburban and outer suburban). It’s assumed households who drive own a new 4 cylinder Camry. BITRE only counts that proportion of car standing costs attributable to commuting.

Although public transport costs considerably less in terms of cash outlays, the exhibit also shows commuting by public transport takes much more time than commuting by car, no matter where a household lives. The extra time is enormous for households living in the middle and outer suburbs i.e. for more than 90% of Melburnians.

For example, the cumulative weekly commuting time for the workers in an outer suburban household who use public transport is 1,326 minutes, whereas workers in neighbouring households who drive only expend 561 minutes per week. Even members of inner city households who use public transport spend more time commuting than members of outer suburban households who drive.

BITRE value the opportunity cost of time spent commuting at average weekly earnings (just over $800 p.w.). With this assumption it’s evident time is far and away the main cost of commuting by public transport, even for households who live in the inner city. That’s a key reason why many argue the focus of public transport spending should be on improving services, not lowering or abolishing fares.

Still, notwithstanding the significant time penalty associated with public transport in Melbourne, it costs inner city and middle suburban households significantly less in total to commute by public transport than by car. Even in the outer suburbs where public transport is at its worst, the total cost on average is pretty much the same according to BITRE.

So why is public transport’s share of work journeys only 24% in the inner city, around 15% in the middle suburbs and below 10% in the outer suburbs?

That’s a good question and I think it could point to a major limitation of BITRE’s analysis – the Bureau doesn’t explain the underlying travel pattern that its analysis is based on. The reader understandably assumes commuters have a choice between two modes for the same trips, but what I suspect the numbers in the exhibit are really showing is the existing pattern of accessibility to employment in Melbourne. And that varies greatly by mode.

At present, public transport users can only comfortably get to a limited number of Melbourne’s jobs, mostly in the CBD and near-CBD. Existing public transport use reflects that limitation – most trips are CBD commutes. However given that a little over 80% of jobs are outside Melbourne City Council’s boundary and relatively dispersed – indeed, 50% are more 13 km from the CBD – most jobs are more easily accessed by car-based commuters.

So BITRE’s figures seem very limited in their application and should be interpreted with that caveat in mind. Having said that, I have some issues with the methodology anyway.

I think it’s possible BITRE has over-estimated the costs of commuting by car, by attributing too much of the standing costs of car ownership to the journey-to-work. BITRE relies on a study by Inbakaran and Shin which assumes 66% of car use by outer suburban households is for commuting and the corresponding proportions for middle suburban and inner city households are 58% and 46% respectively. Unfortunately, Inbakaran and Shin don’t explain how they derived these figures. They don’t sit well in my view with VISTA’s finding that only 33% of travel kilometres in Melbourne are for work-related purposes (or just 22% when measured by number of trips).

I also have some doubts about the overall methodology. BITRE has sought to isolate work trips from other sorts of trips, but the reality is those outer and middle suburban workers who commute by public transport almost all come from households who own a car (or two….). BITRE doesn’t factor in the benefit of having a car for non-work trips – it might indeed cost no more to commute from the outer suburbs by public transport if the household doesn’t own a car, but life in the suburbs for working families without a car is miserable (and they accordingly make up a miniscule proportion of all households in the outer suburbs).

Of course there’s another whole discussion to be had about the social cost of driving to work versus using public transport. That’s for another day.