COVID-19: Transportation Response Center
Measuring the performance of a given street or network is a rigorous and imperfect process. A street that works extremely well for one set of users may be perilous for another, just as an intersection with no delay at one point may mask significant delay along a corridor. Performance measures must take a multi-disciplinary approach, looking at urban streets and traffic at the macro and the micro scale, through the lens of safety, economy, and design, and inclusive of the goals and behaviors of everyone using the street.
The goals of different street users often stand at odds. Bicyclists come into conflict with unloading trucks, pedestrians vie with cars for crossing time at congested intersections, and emergency vehicle response times counter the desires of a community for slow traffic speeds and speed humps. Urban street design must strive to balance these goals, making strategic trade-offs in search of a win-win scenario.
The development of holistic performance measures requires a redefinition of the problem that a designer is trying to solve, as well as recognition that streets are places to sit and stay as much as they are conduits for movement. While a multi-modal performance metric such as person delay may improve upon auto-based level of service (LOS), delay alone fails to capture the success of a city street outside of its ability to move people through it. A street with low “person delay” is not necessarily a great street, especially if it has no economic activity, places to sit and rest, or shade trees to improve the public realm.
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Adapted from the Urban Street Design Guide, published by Island Press.