Conscious Choice: Urban Mobility Problems

January 2002 | Midwest Biking

Urban Mobility Problems

by Floyd and Tobi Mittleman

We were scanning the League of Illinois Bicyclists Web site the other day (www.bikelib.org) and came across some interesting information in the form of the 2001 Urban Mobility Study. This was "The Short Report...For Readers Who Are Not Stuck In Traffic" published by the Texas Transportation Institute, a division of the Texas A&M University. The report documents rising congestion levels on major urban road systems across the United States. (Fortunately the full report was available in the transportation section of the Northwestern University library.)

The report summarizes data taken from sixty-eight urban areas across the United States that have a population of 100,000 or more. The study uses various travel-time measures to evaluate several travel modes. The work began in the early 1980s when the sole sponsor for the research was the Texas Department of Transportation. Eleven state departments of transportation sponsor this new report. The focus of the study is not to suggest solutions to the current transportation problems but rather to provide a source of data that citizens and transportation professionals can use to discuss which projects, programs, and policies should be pursued.

The key measures used to evaluate urban mobility are the travel rate index (TRI) and the travel time index (TTI). The TRI is the ratio of the travel time in the peak period to the travel time in the free flow period. The TTI is a ratio of the travel time in the peak period, including time lost due to incidents such as accidents, to the travel time in the free flow period. The TTI is measured over a longer period of time than the TRI. The TRI for all sixty-eight urban areas is about 1.32. This means that a trip that would take 60 minutes during free flow time would take 79.2 minutes during rush hour (79.2/60 = 1.32). The TRI for very large urban areas is 1.40 and 1.07 for small urban areas.

As you might expect, accidents and other traffic incidents have a significant effect on delay, hence TTIs are much larger than TRIs. In Chicago, the department of transportation works very hard to reduce the time it takes to clear an accident from the roadway. However, on average, mobility is not improving across the United States. Congested periods are getting longer. The rate of daily congested traffic on U.S. roadways increased from 17 percent in 1982 to 33 percent in 1999. In 1982 the roadways were congested for about two to three hours a day. In 1999 the roads were congested for about five to six hours a day.

Will widening the roads or increasing the number of roads decrease congestion, i.e., lower the TRI? Sure. But the problem is much more complicated than this. In the first place, communities cannot afford to build roads at a pace that would keep up with the increase in traffic. What’s more, the public would not approve the building of the number of roads that would be necessary to keep up with growth. And think of the environmental impact of excessive road building! There is also the practical problem that in the most congested areas there simply isn’t enough space to build the required number of roads or to increase the number of lanes on existing roadways.

So what are the alternatives? Public transportation is an obvious suggestion. To accommodate one year’s growth in vehicle travel volume (based on an estimate from real data taken from previous years) it would be necessary to convince 6.1 million additional people across the nation to take public transportation. Looking at car sharing, four out of one hundred vehicles would have to become a new two-person carpool to handle one year’s growth. Are these realistic possibilities? Probably not. And when you look at these real numbers, think what the effect of adding bicyclists to the mix would be. Do you suppose that we could convince an additional 6.1 million people to switch to bicycles each year?

Let’s look at the cost of congestion. In 1999, congestion cost, based upon wasted time and fuel, was about $78 billion in the sixty-eight urban areas covered by this study. That’s an average of about $620 per person. In very large urban areas the cost was greater — $920 per person. What about wasted fuel? Approximately 6.8 billion gallons of fuel are wasted in the sixty-eight urban areas each year. That’s about fifty-five gallons of fuel wasted per person. Do we have a serious problem here? You bet we do. Is there a simple solution? Sadly, no. The authors of this report make it quite clear that their purpose is not to provide answers to the travel congestion problem but rather to provide information to provoke discussion in communities around the country.

The report makes a couple of things clear, however. We are not doing enough. We cannot solve the mobility needs by constructing more roads. Transit improvements (including increased cycling) do not seem to offer the promise of large increases in mobility, yet they must be included in the overall solution. Policy options such as peak-travel restrictions could improve transportation but they are difficult to get approved. Most large cities have already considered these and many other options, yet congestion continues to grow from year to year. As the authors say, "The‘solution’ is really a diverse set of options that require funding commitments, as well as a variety of changes in the ways that transportation systems are used. The chosen options will vary from area to area, but the growth in congestion over the past eighteen years suggests that more needs to be done."

Remember that these data reflect only the issue of time. Just think what those 6.8 billion gallons of wasted gasoline are doing to the environment! Every time you use your bike instead of your car you are contributing to the solution to this problem.

And that, of course, brings us to the reason that we logged on to the League of Illinois Bicyclists Web site in the first place. We had received the postcard from LIB reminding us of the roadwork being planned for our town. We were admonished to consider what must be included in this work to make the roads more bicycle friendly and to report this information to the league. Do your part by letting the league know what you think should happen to the roads in your neighborhood. Check it out at www.bikelib.org.

Meanwhile, get out your bike, ride, and above all stay healthy.

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