Walkable City: How Downtown Can Save America, One Step at a Time

by Jeff Speck

many cities across the country are finding it politically possible to introduce something called a “road diet.” In a road diet, a standard four-lane street is replaced by a three-lane street: one lane in each direction and a center lane reserved for left turns. What is remarkable about road diets is not that they save lives—that is to be expected. In a typical road-diet conversion, Orlando’s Edgewater Drive, the number of crashes fell by 34 percent and, because the crashes were slower, the number of injuries fell by an impressive 68 percent: from one per nine days to one per month. Rather, the surprising thing is that they do not reduce a street’s carrying capacity. Thanks to the inherent efficiency of maintaining a dedicated turning lane, the typical road diet does nothing to lower the traffic volume on a street. Comparison of seventeen different road diets conducted by the engineering firm AECOM found that only two streets lost capacity, while five stayed the same, and ten actually handled more cars per day after the conversion.