Urban Mobility Report Points to Overbuilt Roads in St. Louis

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The Urban Mobility Report published earlier this year revealed a surprising dichotomy about congestion in St. Louis. Despite congestion continuing to decrease since 2000 as represented by the report's travel time index statistic shown on the right, travel time for the average St. Louis commuter has increased.

As mentioned before, the reason for the dichotomy likely lies with the sprawling nature of St. Louis's suburbs. Between 1950 and 2000, St. Louis's urban population grew 48% while urban land area grew over 260%.

The difference between population and land area, however, tells only part of the story; it shows how thinly the region's infrastructure is being stretched. The data underlying the Urban Mobility Report tells another part; it shows that our road infrastructure is likely overbuilt.

According to the Urban Mobility Report, since 1982, the total number of lane miles in the St. Louis urban region (areas with densities greater than 1,000 people per sq. mi.) has more than doubled from 3,145 miles in 1982 to 6,615 miles in 2009. Over the same period, however, the region's population utterly failed to keep pace with the flurry of road building and grew by only 25%.

It therefore goes without saying that, over the same time period, the number of people per lane mile of road has plummeted by 40%.

But that statistic alone doesn't yet explain why congestion in St. Louis has decreased so significantly. One of the stories of the past few decades is the rise and dominance of the automobile, not just in the design and relentless building of roads and highways, but in the planning of cities and the built environment with the sprawling of American cities forcing people to make ever longer commutes. But the pattern of ever-longer commutes, at least in St. Louis, is changing.

In 1982, the average person in St. Louis drove just over 12 miles everyday. Over the next 9 years, this statistic rose steadily to 15.2 miles travelled daily per person. Between 1991 and 1995, DVMT spiked to over 20 miles per capita. Then something funny happened. The length of people's commutes leveled off. And with the exception of a blip in 2007, commute lengths have decreased ever so slightly.

All of the above brings us to one final statistic, DVMT per lane mile. This statistic is a basic measure of the relationship between highway travel and highway capacity.

Between 1982 and 1991, DVMT per lane mile remained static as road building kept pace with the increase in driving by St. Louis commuters. Over the next 4 years, however, DVMT per lane mile increased sharply due to the corresponding spike in DVMT per capita. But after DVMT per capita leveled off, DVMT per lane mile began to steadily decrease where, by 2009, it was almost at its lowest levels ever. And with anemic population growth and continued road building, DVMT per lane mile (and the TTI along with it) will likely continue its downward trend.

the Page Avenue Extension is one project that added significant capacity to St. Louis area roads
{the Page Avenue Extension is one project that added significant capacity to St. Louis area roads}

2010 Urban Mobility Report_data for Saint Louis, MO

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  • stev0205

     The condition of city roads alone should show you that our MODOT money is not spent wisely. We can build ’em! but damned if we should maintain them!

  • Mark

     This honestly doesn’t surprise me in the slightest.  I live and work in South City and it takes me 15 minutes on a bad day to get to work, door to door.  Many of my co-workers have over an hour commute _each way_!  I’m not sure why.  They go to restaurants and hang out in the city, but then they drive back to the burbs.  Living the dream, I guess.  That’s a lot of time on the Interstate though…. for no reason.

  • Zun1026

    Was this report, coupled with the ongoing lack of supportive funds for MODOT, the reason why there is a hold on new projects? Regardless, I have long suspected that not only was the expansion of lane capacity unnecessary for traffic congestion relief, but it further fueled sprawl…along with poor regional and local planning.

    • No, MoDOT’s problems are simply due to a shortage of revenue. The suddenness of their problems is half their one doing (bonding Amendment 3 revenue), but was also inevitable (gas tax). I’ll explain that a bit more next week.

      • Zun1026

         I had heard form a transportation planner at MODOT, who believed this was inevitable (both the funding issues and the move to just maintaining) and that prediction was made back in 2007 or 2008…can’t put a finger on the exact year. 

        • tpekren

          Pete Ryan, former head of MoDOT, was stating the obvious as early as 2007.  I don’t believe their was any surprises in MoDOT or the the contractor side of things that this was coming.  Politics conveniently ignored it.

          The plus side in my opinion, Financial reality might actually bring new lanes miles to a screeching halt.  This might not be all bad news for a metro area that has more then adequate highway capcity.

          • Zun1026

            I am with you on the “this could be good” line of thought. 

            I found it hard to believe that MODOT funds were sudden.