You know you’re a transport geek when you find yourself at a 9 PM debate about how governments should measure “urban mobility.”
The opportunity arose one night at the Congress for the New Urbanism conference in Madison last week. Long after most urbanists had adjourned to the bars and restaurants, a small but sharp audience gathered to hear Tim Lomax of the Texas Transportation Institute (TTI) debate Joe Cortwright of CEOs for Cities. Tim was there to defend TTI’s influential Urban Mobility Report (UMR), an annual compendium of statistics that are widely used to define how US cities think about mobility problems and to benchmark these cities against each other. Joe was there to attack TTI’s methodology as biased against compact, sustainable cities.
The technical core of the argument is simple. TTI’s Travel Time Index, one of their more quoted products, is a ratio of peak congested travel times by car against uncongested travel times by car. In other words, travel times are said to be “worse” if they get much longer on the peak than they are midday.
This ratio inevitably gives “better” scores to cities where normal uncongested travel times are pretty long — in other words, spread-out cities. Here’s the CEOs’ critique of how the TTI compares Charlotte and Chicago: