Toward livable streets: A review of recent improvements in practice and four general principles of livable streets engineering

In the last decade a number of project development and design guides, such as ITE’s “Designing Walkable Urban Thoroughfares,”  NACTO’s “Urban Street Design Guide,” and city design guide manuals, have emerged. A new article by Eric Dumbaugh of Florida Atlantic University and Michael King of BuroHappold Engineering, reviews these updated practices.The article finds four general principles of livable streets engineering:

1. Examine networks and person capacity during the alternatives analysis process..…When establishing a project’s scope and evaluating project alternatives, planners should include not only the identified corridor but also the surrounding network in their analysis. Conventional planning practice strives to direct traffic onto streets designated as “arterials.” Yet in urban environments, a significant portion of traffic is likely directed not for distant destinations but toward local “microdestinations” in the surrounding area (Jacobs 2004). Indeed, it is for this reason that destination accessibility (by automobile) has proven to be the design variable with the most profound effect on reducing VMT followed closely by street network connectivity (Ewing and Cervero 2010). A significant portion of the traffic delay along an urban corridor may be addressed by simply providing more direct means for allowing people to get where there are trying to go….

2. Establish target speeds between 20 and 35 mph.Twenty mph is the maximum speed at which a pedestrian or cyclist can be struck by a vehicle and survive, leading many European countries, as well of the World Health Organization and the OECD, to recommend the adoption of 20 mph as the target speed for urban streets where pedestrians are likely to be present. The use of 20 mph target speeds has yet to be adopted as a model practice in the United States, with the design guidelines and practices reviewed in this article recommending target speeds of 25 to 35 mph. A review of the scholarly literature suggests that the upper limit for safe urban streets is 35 mph. On-street parking appears to reduce total and injurious crashes at speeds up to thirty-five mph, but exacerbates crash risk at higher speeds. Similarly, crosswalks tend to have detrimental effects on pedestrian safety at speeds of 40 mph or greater and no effect whatsoever on encouraging motorists to yield to pedestrians. As such, 35 mph is likely the upper bound for desirable target speeds on urban streets.

3. Develop consensus on design controls during the early phases of the project.The design of a street project can change dramatically as the project vision enters the engineering phases of design. This can create conflicts between planners and engineers, as the initial project concept is modified based in the design controls applied by engineers. Many of these problems can be avoided by developing consensus on the project’s traffic volumes, design vehicle, and design speed during the visioning and alternatives analysis phases of the project and being attentive to available strategies for addressing the challenges associated with application of specific design controls…

4. Focus on intersections and safe crossings, rather than lane widths and curb radii.[L]ane widths and curb radii, by themselves, are not a silver bullet for creating walkable streets. … The spacing and timing of controlled intersections, the use of roundabouts and traffic circles, bulb-outs, and the provision of protected pedestrian crossings are strategies that will likely be more effective at reducing vehicle operating speeds and addressing the broader design goal of ensuring that pedestrians can cross streets safely and comfortably….Eric Sundquist is Director of SSTI. Among other barriers, low-wage workers face discrimination based on commute distance

Along with lack of access to transportation options in areas outside the urban core, low-wage workers also face another obstacle in finding work. Discrimination by commute distance is significant when applying for low-wage jobs, concludes a new study. Affluence and long commutes, however, may not affect decisions to call applicants back.The experiment, conducted in Washington, D.C., consisted of sending 2,260 resumes to 565 job listings requiring only a high school diploma and requesting a mailed or emailed application and resume. The fictional resumes fall into four categories: near and poor, near and affluent, far and poor, and far and affluent based on characteristics defined by the author.In the following maps, the author illustrates the spatial disparity for low-income workers. The first shows where workers earning $1,250 per month, or less, live; the second shows where they work. For scale, the northwest side of the District measures about 10 miles.

Callback rates decrease by 1.1 percent for each mile an applicant lives from the job, with affluence held constant. Applicants with a 5- to 6-mile commute were called back 14 percent less frequently than those with an average commute of 3 miles. Since non-white Washington, D.C., residents on average live nine tenths of a mile farther from jobs than white residents, non-white residents can expect one percent fewer callbacks regardless of where they live. Applicants with stereotypically African-American sounding names are called back 6 percent less frequently than those with white sounding names, according to the study.The author calls into question the effectiveness of programs designed to move low-wage workers into more affluent neighborhoods, and suggests that moving to areas where jobs are closer or more accessible (by transit or other means), would improve employment opportunities and perhaps diminish employer discrimination.Even in a fairly dense urban environment with a passable transit system, discrimination over the small difference in commute distance of 2 or 3 miles is significant. It is not a huge leap to imagine that this discrimination may be more widespread, existing in less dense cities where commute times can be significantly longer.As cities become more attractive to high-wage workers, due to their proximity to jobs and other amenities, the resulting higher cost-of-living forces lower-income populations into lower-cost areas such as the suburbs, where transportation to low-wage jobs can become an issue. Transit from suburbs can be cumbersome, and congestion can cause long, unreliable auto commutes. Discrimination based on commute distance compounds the difficulty faced by suburban lower-income populations.Building lower-income housing near transit and jobs, improving transit, and using demand managementto improve the reliability of commuting by auto, as well as adequately funding transit, are important measures to alleviate the spatial disparity between low-wage workers and low-wage jobs.Michael Brenneis is an Associate Researcher at SSTI.