I'm old enough to remember the episode of The Simpsons when Homer Simpson, after 22 minutes of serial idiocy, wraps up the show by proudly declaring: "Marge, my friend, I haven't learned a thing."

Well, it seems that British Columbia's transportation officials are now treating The Simpsons as an instruction manual.

As I pointed out a few months back, British Columbia's transportation planners have long been nursing a delusion that traffic across the Port Mann bridge will magically start to soar any day now… even though actual travel across the span has trended downward for the better part of a decade.

And they've apparently done it again:

There are 5,000 to 6,000 fewer cars a day on the bridge, compared to traffic prior to the toll being introduced a year ago, said Todd Stone… "But we expect that those numbers will bounce back as people really sort it out, and determine: how much is their time worth?"

Revenue forecasts for the next three years are being adjusted to 20 per cent lower than first anticipated: to $144 million for fiscal 2014, $159 million for 2015 and $174 million for 2016.

So revenue is down by 20 per cent… but still projected to rise rapidly in the next few years!

I have yet to see the official traffic forecasts underlying those revenue projections. But I think it's a pretty safe assumption that they're projecting that revenue will rise in step with traffic volumes. Port Mann tolls don't vary with the time of day -- a car pays $3 to cross the span, whether it's at rush hour or the dead of night. And tolls are slated to rise only at the pace of inflation, capped at 2.5 per cent. Reverse-engineering the traffic forecasts, along with estimates of traffic trends over the past two years, I get this chart:

Just to be clear, the light blue dotted line may not be perfectly accurate. I haven't accounted for changes in the mix of motorcycles and heavy trucks, or any shifts in enforcement or other toll revenue. Nor do I know what inflation rate the province is expecting. (I plugged in two per cent into my estimates.)

Still, I bet that the blue line is pretty close. And if it is, it reveals something truly remarkable: rather than adjusting their their forecasts to match reality, B.C.'s transportation officials doubled down on projections that have repeatedly been proven wrong.

Marge, they haven't learned a thing.

Clark Williams-Derry is deputy director of the Seattle-based Sightline Institute, where this article first appeared.