Density and congestion, etc.

Whenever I see new data on cities, I’m always tempted to match them to the cities’ weighted densities, if for no other reason than no one else does it.  And so with the Texas Transportation Institute’s latest report on city congestion.  TTI found a wide range in hours lost due to congestion per year — e.g., in 2007, Lost Angeles drivers lost an average of 70 hours per year to congestion;  Cleveland drivers, just 12.  (The relevant TTI table is here  (pdf).)  Does weighted density partly explain this variation?

The answer is “No,” based on my admittedly simplistic analysis.  

Below the jump I have three charts plotting, for 33 cities, weighted density, standard density and total population against hours lost per traveler to congestion.   (The 33 cities include the 31 largest urbanized areas — excluding New York City, which is always an outlier — and Austin and Honolulu.) 

As the scatter plot shows, weighted density explains virtually none of the variation in congestion (adjusted R² = .06).   Standard density explains a bit more  (adjusted R² = .19).  And total population, a bit more than standard density  (adjusted R² = .28).