Suburban Nation - Andres Duany [32]
Pedestrian-friendly geometries: a traditional small curb radius slows cars down and shortens crossing distance
Highway geometries applied to the residential neighborhood: a large curb radius doubles both pedestrian crossing distance and automobile speed
A similar circumstance surrounds another aspect of street design, the minimum center-line radius, which controls how sharply a street is allowed to bend along its trajectory. Under current standards, streets are allowed only to curve loosely, with the result that one finger on the steering wheel and one foot on the gas pedal are all that it takes to maneuver through a residential neighborhood. The intention is to provide greater safety by allowing drivers to see farther in front of them, but the result is that drivers feel comfortable driving at higher speeds, making walking all the more dangerous. am
When it comes to street curvature, like curb radii, what works best for cars hardly works at all for pedestrians.
One would think that, after many years of building such streets and witnessing the results, the engineers—at least some of them—would have added pedestrian- and bicycle-friendly standards to their repertoire. However, Paul Box, the nation’s ranking expert on subdivision street design, had this to say when asked how streets might better accommodate bicyclists: “ … the purpose of the Subdivision Guidelines is to enhance safety and livability. Any statements encouraging bicycle use would not likely address these objectives.”an Presumably, we should be grateful that bicycles are still legal.
In truth, a number of engineers have accepted more reasonable design standards, but in most cases there is one thing that prevents them from putting those standards into practice: their manuals. Engineers are exposed to substantial liability in their work. The most surefire way for them to avoid losing a lawsuit is to follow the engineering manuals precisely, no questions asked. Because pedestrian-friendly streets are not specified in the manuals, they are simply not possible, despite all the evidence encouraging their use.
The reaction of most municipalities to speeding has been not to question the standards but simply to post hopeful speed-limit signs, resulting in some rather ludicrous scenarios. In Toole, Utah, we have driven on straight streets forty-two feet wide with a posted speed limit of 30 mph. These streets were perfectly navigable at 65 mph, since that was their design speed, and that was indeed the speed at which we drove, even though we were in a quiet residential community. Posting speed limits to slow traffic on high-speed roads is futile, because people drive at the speed at which they feel safe—and teenagers drive at the speed at which they feel dangerous. Generally, the only time that people don’t speed in modern suburbia is when they are lost, which is, fortunately, quite often.
In addition to narrow streets, another factor that contributes mightily to pedestrian perceptions of safety is on-street parallel parking. Parked cars create a highly effective steel barrier between the street and the sidewalk, so that walkers feel protected from moving traffic. They also slow traffic, because drivers perceive potential conflict with cars pulling in and out. Additionally, parallel parking supports pedestrian life by delivering people to the sidewalk. Since drivers are seldom able to park directly in front of their destination, they often walk past shops or houses other than the one they are visiting. If on-street parking is, for this reason, slightly less convenient, it is one of those small inconveniences that make life more interesting. While many towns and cities have rediscovered parallel parking, it has been on the decline for decades, frowned upon