Streets
Chapter 8 of the New Urbanism Best Practices Guide
Streets are a crucial element of urban design. This chapter explores how to design walkable, safe, attractive streets, starting with a primer on the physics of street design — what design speed to aim for, how traffic capacity varies with speed, how rapidly stopping distances and danger grow with increases in speed. The carrying capacity of a traffic lane is greatest at 25 to 30 mph. A car going 30 mph has more than double the physical impact of a car going 20 mph. In urban settings, conventional street standards cause danger and discomfort, especially for pedestrians.
Street networks are generally safer and more convenient when they’re highly connected, as in a dense grid. The grid slows and disperses traffic, giving motorists more choices of routes. With more streets, each one can be narrower and more human-scale, which also encourages people to drive less and walk or bicycle more. On-street parking further diminishes speeds, and enhances safety. This chapter discusses “context-sensitive design,” traffic-calming, tailoring the street network to the six Transect zones, and initiatives to make harsh arterial roads more congenial — in some cases, converting them to boulevards. Replacing freeway segments with boulevards or other gracious streets has spurred real estate investment and neighborhood improvement in Milwaukee, San Francisco, and elsewhere.
Other topics covered: one-way couplets; changing one-way streets to two-way; designing corners to slow vehicles and aid pedestrians; installing roundabouts; the European concept of “shared space”; design of street edges (on-street parking, tree lawns, walkways, enclosure, and transparency); designing for emergency response; solutions at citywide scale; solutions at neighborhood scale; how to promote bicycling; and bike facility planning. Concludes with 12 pages presenting a full set of thoroughfare sections for New Town at St. Charles, Missouri, including residential and commercial streets, alleys, avenues, drives, and passages.
