Wednesday, January 6, 2010

Public transport efficiency in a standard work week environment

There has been a running discussion between Cameron Murray and myself in the comments section of one of his blog entries and I decided the issue deserved a blog entry unto itself.

As a throw away comment, I mentioned that there may be some efficiencies in public transport provision stemming from the standard work week. I may have started something here I cannot finish but I'll try anyway.

Increasing the use of public transport utilisation is efficient in that it reduces the average cost of provision, it reduces expenditure on private motor vehicles and it reduces the environmental externalities resulting from private motor vehicle trips.

The standard workweek increases the convenience of public transport and, as such, increases the number of people utilising public transport services. Ceteris paribus, increasing the number of people using public transport reduces the average* cost of provision per user.

Furthermore, on a general equilibrium level, having strong public transport utilisation provides significant efficiency benefits to society through reduced investment in, and use of, private motor vehicles. For example, if every bus takes two full loads of commuters to work each day, it would reduce the number of motor vehicle trips by over 100. This reduces commuters’ need to purchase a car and reduces the environmental externalities coming from the saved trips.

So, if there are efficiency benefits from improving public transport utilisation, how can we make public transport attractive to commuters? By making it convenient.

Taking a step closer and looking at only the efficiency of public transport provision (as opposed to efficiency of society), there is always going to be a trade of between efficiency and convenience in public transport provision (up until the point where there is sufficient critical mass in a city to efficiently provide constant public transport services – every ten minutes or so, 24-7).

The idea of inefficiency in public transport provision comes from having capital (both human and mechanical) being underutilised or lying idle. Having an even flow of people throughout the day (as opposed to a standard workday with peaks in the morning and afternoon) could mean that the same number of people could be serviced by fewer busses and trains. And this would be seen as an efficient outcome: i.e. if the same number of people could be serviced by public transport with fewer resources dedicated.

However, public transport utilisation, (as opposed to provision) is linked to efficiency in the convenience sense (and the economic sense on a societal level). In order to make busses and trains attractive to commuters, services must be far-reaching and constant, at the times when people need them. If services are not convenient – both in timing and route – the number of people utilising public transport will be low.

Moving away from the peak-period public transport would considerably reduce the convenience and thus utilisation on public transport. By moving away from peak periods to an even-flow of commuters throughout the day, the average time a commuter has to wait for a bus or train would increase (because the services would not be as regular as they are in current peak times) and the average distance that commuters have to travel to get on public transport would increase (because services to outlying areas would become unviable).

As such, the number of people using public transport would decrease over time because it would be inconvenient to use it. This would reduce the efficiency of the public transport system and society as a whole.

I guess if we break it down to first principles, in both an even-flow** and a peaky workday model, there would only be two efficient public transport provisions:

(1) zero investment with zero commuters (which would be inefficient for society as a whole); or

(2) a city with 24 hour critical mass to run constant services 24-7 – of which there are few examples in the world, perhaps Manhattan and Tokyo could be efficient.

As such, if efficiency in public transportation is the goal, irrespective of whether we are an even-flow or peaky workday economy, we should have no public transport.

If instead, efficiency in the economy as a whole is the goal, then the model that would meet the needs of a greater number of commuters would be the most efficient.

To me, that would clearly be the peaky workday model.

*marginal costs in infrastructure investment often provide poor a measurement of effeiceincy due to the peakyness of investment. e.g. the MC of adding one person to a full buss is the entire cost of a new bus, the MC of adding a second person is (near to ) nothing. As such, while a little rough, average cost is a useful tool when measuring efficiency.

**every time I type even-flow I’m reminded of Pearl Jam... “thoughts arrive like butterfli-ies... oh, he don’t kno-ow so he chases them awayayay".

(I'd also like to note the irony of two cyclists arguing about PT).

1 comment:

  1. Yeah, maybe we should move the discussion along to the most effective ways to promote cycling or some such thing. I'm sure we can settle this with some evidence from cities around the world. There must be a some good papers on exactly this issue.