Well I’ve spend a couple of hours digging through information on oil prices, petrol prices, state highway traffic levels and public transport patronage, to hopefully come up with some interesting information on the relationship between petrol prices and transport.
Logic tells us that as petrol prices increase we would expect fewer people to drive and more people to catch public transport. When we look at what has happened to petrol prices, traffic levels of state highways and public transport patronage since January 2007, we do see that trend to some extent, although there are enough exceptions (especially in terms of public transport patronage, which varies a lot month to month) that the relationship seems a bit more complicated than I had potentially thought. For a start, here’s the table I put together:
The trend seems most obvious throughout 2008, where between March and September we saw petrol prices above $1.80 a litre, significant decreases in road use, and significant increases in public transport use. If we look back at 2007 we can see for most of the early part of that year petrol prices were significantly lower than they had been throughout 2006, and as a result traffic volumes were also up on the year before. Public transport use throughout 2007 was pretty poor when compared to 2006 levels, in that while patronage did still increase it was not what might have been expected. So I guess the trend held there too: lower petrol prices, more people driving, less people (comparatively to what might have been expected) catching public transport.
That trend seems to have disappeared in 2009 though. Ever since November last year we’ve seen significant reductions in petrol prices – with prices being up to 30-40c a litre cheaper than they were in the same month of the previous year. However, with the exceptions of a few months (most notably July 2009) we haven’t really seen state highway use recover the ground that it “lost” during 2008. I guess quite a lot of that might be due to the recession, but the public transport trends also show us something quite interesting. Put simply, it really does appear as though people who first tried public transport in 2008 due to the higher petrol prices – have decided to stick with it this year, even though price of petrol has come down a lot.
The graph below shows the clear trend between petrol prices and traffic levels, although as can be seen the relationship with public transport use is a bit less obvious:
Months where the yellow line is above the pink line shows that public transport patronage growth is higher than state highway traffic growth. No surprises that it mostly happened when petrol prices were highest.
It’ll be interesting to see what happens in the next few months. Perhaps the lower prices will finally kick through into more traffic growth compared to public transport growth?
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You would expect the yellow line to mirror the blue very closely wouldn’t you…
Is that big uptick in May ’08 the Northern Busway perchance..?
I guess it is a lot more complicated than I’d have thought, things like new infrastructure and consumer confidence affect the situation more than one would naturally assume…
There seems to be a 3-4 month lag between petrol prices changing and traffic/public transport levels responding. I guess that it was the “second peak” that led to the $2 or more prices that REALLY affected things.
The Northern Busway fully opened in February 2008. However, since that time patronage on it has continued to grow dramatically month by month.
There doesn’t seem to be any adverse effect on PT use with the increase in bus fares either, I think the price went up early January this year? As an aside, I’d be interested to know where ARTA get their patronage data from. I can’t find reference to it in their reports. It’s my understanding that they don’t actually get great data from the bus companies. Maybe they get total patronage (which would be enough for this level of information) from bus companies but not broken down by service/day/time? Anyhoo, good work on the number crunching!
The ARTA data isn’t great actually. Last time bus fares increased was probably 2-3 years ago I think.
It’s an interesting analysis Jarbury and now that oil prices are back on the up and up, now at 82 odd dollars being higher than anytime during 2009, it will be an interesting year 2010 I think. I’ve always felt that oil prices and international climate change policy that NZ has to stick to, are really the only two things that could potentially rain on the Nat’s road fest parade and perhaps bring some sanity back to transport planning in NZ. Because, it would seem it doesn’t matter what any of us says they’re still going to build roads unless they’re somehow forced to change their ideas.
Heh, this is an old post you’ve dug up. I agree with you fully though: Joyce’s transport policies would look pretty silly with petrol at $2.50 a litre and affordable electric cars still many years away.