Friday, August 2, 2019

Road diets

A satellite photo of Jackson Ave. during its reconfiguration. If you look closely, you can see the ghostly shadows of orange barrels.  

Gentle readers. I want to write a little bit about road diets. There are three road diets on Monday's #a2council agenda: DS-1, DS-2, and DS-3. A road diet, sometimes called a road reconfiguration, is when the total number of travel lanes on a road are reduced to allow for other uses and travel modes. E.g. a 4 lane road is reduced to a 3 lane road. This frees up space to add bike lanes and to add features that make pedestrians safer. Road diets also make roads safer for drivers by reducing the number of crashes on a road segment. If you are interested in a deep dive, the Federal Highway Association has a great 72 page report on road diets.

Ann Arbor has implemented several road diets in the past few years including on Jackson Road and Maple Road. On July 16th, a memo examining recent road diets was sent to the Transportation Commission. It too, is worth a read. Looking at 5 recent road diets, total accident counts dropped between 20% and 65%. Here are charts looking at specific crash rates from the Jackson Road project and the Green Road project:

The Green Road Road diet is one of the poorest performing and I wanted to highlight it because it still shows an overall reduction in the average number of crashes.

Road diets also offer great benefits to pedestrians and cyclists. By adding more room for them, and buffering them from cars, road diets increase safety for non-motorized transit. They also tend to increase usage. You can find more in this document from the Federal Highway Administration in section 2.1.3.

One drawback for road diets is that is that they can slow down traffic during peak flow periods. A recent survey of Ann Arbor residents showed that the majority support these minor reductions in traffic flow in exchange for greater safety for motorists, cyclists, and pedestrians. Here are the results:


  1. Where are these mythical cyclists? I drive from Briarwood to Pontiac Trail every day and never see more than one cyclist the whole time. Furthermore, this is not PORTLAND, our cycling season is about 4months out of 12 except for a few diehards who relish snow, ice, rain, and sleet.

  2. A road diet *may slightly slow traffic at peak times, but the accidents that result from the current design of roads definitely significantly slow down traffic.

    Walking at Green road and Traverwood road yesterday during peak rush hour, there was extremely light traffic. These roads are fantastic candidates for road reconfigurations, and I hope council does the right thing and approves these plans.

  3. Victor, I've lived in Michigan most of my life, and I never realized it snowed eight months of the year.

    One of the US cities with the highest rate of cycling is Minneapolis - not known for its mild winters. I bike through the winter; with proper equipment, I find it much warmer than taking the bus.

    1. I realize this is an old exchange but I wanted to chime in that I cycled for 12 of my 18 years to and from work in MPLS year round except for the bitterest cold days. MPLS has fully protected bike paths with dedicated snow removal equipment. I fully intended to cycle when I moved here but didn't last a week because distracted drivers and ridiculous (discontinuous, blocked by various things, unprotected) bike paths make it too dangerous for my tastes and skill level.