For those of us who are obsessed by oil prices, it’s a fun time to be alive: crude oil spot prices just topped $48 per barrel. That means that prices have risen more than four-fold in under six years.

Now, commodity prices are inherently volatile. But it appears that oil prices, after a long period of relative stability, are becoming more unstable by the day.

That doesn’t mean that prices are going to maintain their upward trajectory indefinitely; volatility implies collapses as well as spikes in oil prices. But at a minimum, the people who are most involved in thinking about the future implications of oil prices—and here I’m thinking most especially of the region’s transportation planners—ought to start giving a closer look at the long-run implications of rising and volatile oil prices on today’s decisions about transportation infrastructure.

So far, rising prices haven’t put much of a dent in oil consumption in the region, if any. Short term price volatility doesn’t have much of an effect on how much people drive. But over the long term, high prices start to shift people’s behavior, either by encouraging more fuel efficient vehicles or by promoting a mode shift away from cars and to transit.

But most traffic projections assume that oil prices will remain constant—which may mean that we’re overestimating how much traffic the Northwest’s roads will have to support 30 years from now.

And, just as a side note—in the time it took me to write this post, oil spot prices climbed another 50 cents, to just under $49.