Earlier this week, the U.S. Department of Transportation announced an 18-month campaign to improve road safety across the country. One of the things DOT plans to do is create a guide to “road diets” that it will distribute to communities and local governments. DOT says that road diets can reduce traffic crashes by an average of 29 percent, and that in some smaller towns the design approach can cut crashes nearly in half…
The result was a much safer road. In small urban areas (say, populations around 17,000, with traffic volumes up to 12,000 cars a day), post-road diet crashes dropped about 47 percent. In larger metros (with populations around 269,000 and up to 24,000 daily cars), the crash reduction was roughly 19 percent. The combined estimate from all the best studies predicted that accidents would decline 29 percent, on average, after a four-to-three-lane road diet—DOT’s reported figure.
These benefits alone would be enough to merit more road diets, but there were plenty of others. Bicycle and pedestrian traffic tends to soar at these sites, as the recaptured road space gives way to bike lanes or street parking that provides a sidewalk buffer from moving traffic or crossing islands, and as vehicle speeds decline (especially for high-end speeders going more than 5 miles per hour over the limit). Traffic volumes, meanwhile, typically stay even in such a corridor: some drivers diverted to other parts of the street network, while the rest quickly soak up any vacated space.
Best of all, these kinds of changes don’t cost much. When timed with regular road maintenance and re-paving, road diet policies require little more than the paint needed to re-stripe lanes. They’re about as cheap and cost-effective as infrastructure improvements get, which has led some to wonder why the technique isn’t used more widely.
This is counterintuitive: many people would guess that adding lanes to roads makes driving better. I would guess many people fed up with traffic in their community wouldn’t immediately support road diets. Yet, evidence consistently suggests that adding lanes attracts more traffic and that narrow roads prompt drivers to pay more attention and reduce their speed.
The City of Wheaton introduced this years ago on Main Street. The road used to have two narrow lanes in each direction between the railroad tracks and Cole Avenue but this was changed to two lanes in each direction with a median/turn lane. Traffic today seems to move just fine and the median/turn lane helps isolate turns and limit situations where big vehicles in small lanes presented hazards.