What City Observatory did this week

1. Another tall tale from the Texas Transportation Institute. This week, TTI released another episode of its “Urban Mobility Report,” claiming to measure the cost of congestion and track the continued worsening of traffic in American cities. The problem, as Joe Cortright explains, is that these reports are riddled with problems that TTI has declined to address. From failing to distinguish between mobility (the ability to travel great distances) and access (the ability to actually get to the places you want to be); to comparing data from years that used wildly different and incompatible methodologies; to ignoring evidence that adding roads has failed to reduce congestion even by TTI’s own metrics, it’s either time for the “Urban Mobility Report” to wise up, or for reporters to stop giving it such credulous coverage.

2. Are racial tipping points overblown? Daniel Kay Hertz looks at the popular idea of the “tipping point”: the theory that very mild racial housing preferences can lead to total segregation if just a few people of color move into a previously all-white neighborhood. While the theory is elegant, it turns out that the actual evidence is much more mixed, and there is good reason to believe that tipping points are no longer a major factor in most American neighborhoods. That’s important both for our understanding of why segregation happens, and for giving us reason to believe that more integrated urban communities aren’t an impossible dream.

3. Growing e-commerce means less urban traffic. Joe Cortright examines the potential effects on vehicle travel of increasing reliance on online delivery retailers like Amazon. Because these purchases reduce individual trips to brick-and-mortar stores while increasing the delivery density (and therefore efficiency) of delivery trucks, more e-commerce is probably creating a net negative impact on urban vehicle miles traveled.

4. New Orleans’ missing black middle class. Joe Cortright digs a little deeper into an article by FiveThirtyEight‘s Ben Casselman, who reports that the ranks of New Orleans’ black middle class has shrunk substantially since Hurricane Katrina ten years ago. Cortright finds that this narrative only applies to the city proper, however: New Orleans’ suburbs have seen an increase in middle class black residents, strengthening a trend that existed even prior to the hurricane.

The week’s must reads

1. Transportation for America reports that Phoenix’s voters have approved a sales tax increase that will generate more than $17 billion over 35 years to expand the famously sprawling city’s public transit network. Importantly, much of that money will be used not just to build new infrastructure, but to improve service—including adding frequency on bus lines. About 28% of the funds will go to tripling light rail capacity, and 7% will improve city streets, sidewalks, and bike lanes.

2. Robert Puentes at the Brookings Institution is also skeptical of TTI’s “Urban Mobility Report,” and asks what it would take to move towards a people-centered understanding of transportation priorities. In particular, understanding the distinction between simply covering great distances and actually reaching the jobs, stores, schools, and homes that people need access to is crucial.

3. At CityLab, Richard Florida writes about the dubious efficacy of “broken windows” policing. Rather than “public disorder” leading to more serious crime, a study by Robert Sampson and Daniel O’Brien finds that escalating private conflict is a much stronger producer of violence. Florida concludes that rather than focusing on physical signs of disorder, cities would be better off with a people-focused policing strategy that seeks to defuse tensions between neighborhood residents.

New knowledge

1. David Levinson, Brendan Murphy, and Andrew Owen of the University of Minnesota investigate the “safety in numbers” phenomenon: the idea that the presence of more pedestrians and cyclists reduces the crash rate for those non-vehicular street users. The authors find empirical support for this idea, showing that intersections in Minneapolis with more pedestrian traffic have much lower pedestrian crash rates. Exactly how the effect works is still unclear.

2. More evidence that segregation is one of the chief barriers to racial equality: Jeremy Fiel of the University of Arizona examines school segregation and resource allocation in American schools between 1993 and 2010. Fiel finds that “school segregation…was highest when and where resources such as teachers and expenditures were more unequally distributed across schools and school districts.” Mandatory desegregation programs, on the other hand, were successful in reducing levels of desegregation.

3. Patrick Button of the University of California, Irvine has bad news for economic incentives. Looking at motion picture production incentives, Button finds that these measures can have effects in areas where different cities are highly substitutable—like filming location—but not in other areas, like employment or the establishment of film production firms. Button concludes that the importance of agglomeration effects overrides whatever benefits the incentives provide.

The Week Observed is City Observatory’s weekly newsletter. Every Friday, we give you a quick review of the most important articles, blog posts, and scholarly research on American cities. You can sign up to get it in your inbox by clicking “Subscribe” at the top of the page!

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