Chart of the Day: Congestion Cost Estimate Ranges

Well, today’s news is dominated by the perennial congestion report released from the Texas Transportation Institute (TTI), which ranks cities based on congestion and then places a monetary value on that estimate. Feel free to read through James’ critique of the numbers, which was published on the site today.

Or check out this chart, from Todd Litman’s article on Planetizen. Litman is director of the Victoria Transport Policy Institute, and has long been something of a nemesis for the TTI. Here’s a chart from his well-sourced article:

congestion cost estiamate range chart

[The Urban Mobility Report uses an upper-bound travel speed baseline and travel time unit costs. Most economists recommend lower values. The lower-bound estimate is based on Transport Canada’s lower baseline speed and the U.S. Department of Transportation’s lower travel time unit costs.]

 

Basically, this shows the possible range of “value” equated with time lost in congestion. Here’s Litman’s explanation of why the TTI’s methodology is flawed…

The Urban Mobility Report’s estimates represent the upper-bound range of possible congestion costs; applying methodologies and assumptions generally recommended by economists and government agencies can reduce these estimates by half or two-thirds. To be comprehensive and objective, the UMR should summarize current congestion costing research; discuss different evaluation perspectives and costing methods; explain why the methods and assumptions it uses were selected; apply sensitivity analysis; compare congestion with other transport costs; account for changing travel demands; consider all impacts when evaluating potential congestion reduction strategies, and provide more transparency, quality control and peer review.

I think the tide is starting to turn on congestion value estimates that rather sloppily equate money and time. What would a more careful accounting of the “cost of congestion” look like?

(Be sure to read James’ article. It focuses precisely on this question!)


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