Thursday, January 2, 2014

Since 1999 US Transportation Forecasts Wrong 61 out of 61 times!

This is old news and has been making the rounds for a couple of weeks now, but it's so very interesting as it impacts the way we plan for future roads and bridges.

Since 1999, in 61 out of 61 projections of vehicle miles traveled sent to Congress by the US Department of Transportation, the actual miles traveled came in way under the projections.

61 out of 61! 100% error rate!

Trend-line mania:  61 out of 61 projections were too high.
Also, the same slope on the trend line always!
That's the sign of a model that's not modeling reality.

Read more at the State Smart Transport Initiative. (And from 2012, an animated gif on traffic forecasting at Sightline.)

Update, January 9th

N3B:  Population Growth  does not equal driving growth!
N3B put together a nice chart showing the way modeling has linked driving and population growth in a linear way, and how that assumption no longer models reality!

January 22nd - And another great chart from N3B.

October 31st -

Here's an interesting chart of GDP projections and another mismatch with reality!

from a note on "Secular Stagnation" by Larry Summers


Salem Breakfast on Bikes said...

Added great chart from N3B

Salem Breakfast on Bikes said...

Added a chart of GDP projections, interesting especially because it has the same form as the traffic projections chart.