Road Diet Seven Years in the Making—Was It Worth Every Minute?


The town allocated public money to try again in 2020, hiring a consultant for $280,000, according to figures provided by Town Engineer Greg Sommer. The consultant recommended a six-month trial project that began in September of 2021. 

Measured by trial period data, there was a significant reduction in crashes (down to 16 in a six-month period from a high of 51) and a slight reduction in speed. According to speed data in the consultant’s report, the 85th percentile speeds along North Main Street between Fern Street and Asylum Avenue were 46 mph northbound and 48 mph southbound prior to the road diet trial implementation. During the road diet trial, the 85th percentile speeds at this location were reduced to 39 mph northbound and 44 mph southbound, for a net reduction of 4–7 mph. 

A very notable change in the crash data was in the category of side-swipe crashes (from lane changes) which were reduced to four from a peak of 27 in 2020. 

A final recommendation from the consultant is to allocate an additional $330,000 to pay for some widening of the right of way at one end of North Main to allow for five-foot-wide unprotected bike lanes for the length of the project area, a new signalized non-motorized crossing and some signal timing modifications. Another $60,000 provided the road striping changes, signage, and traffic signal modifications, but not a new bridge that needed to be rebuilt, anyway. Total cost: $745,000.

Road diets are meant to be cost effective, but they don’t always work out that way because they face massive public headwinds. A big, controversial road diet I advocated for in Anchorage, Alaska, involved a lot of new construction and took 20 years and at least $10 million of bonded debt for less than a mile of improvements. 

So is it worth doing? 

Road diets save lives and prevent injuries and property damage by making it safer for everyone using the roadway, especially people who are driving cars, the largest group of users for any arterial roadway. It’s become more and more of a common practice on crash-prone roads below a certain volume threshold (less than 20,000 per day) to reduce travel lanes and add a center left turn lane, the basic mechanism of a road diet. 

These projects inevitably cause controversy when they are proposed because it doesn’t make sense to non-engineers that removing half of the travel lanes from a four-lane roadway like North Main Street in West Hartford can make the road safer and more efficient, with only a minimum of increased travel time. 

It’s counterintuitive, but at certain flow rates the lack of interference from turning traffic, especially left turn movements, makes the roadway more predictable and more smooth flowing. Sideswipes and rear-end collisions can be reduced by almost half. An Iowa Department of Transportation public education project explains in further detail how these changes in traffic movements reduce friction and turbulence—much like the fluid dynamics of water flowing in a pipe—to make traffic flow more efficiently.

Besides improving traffic flow, road diet benefits include reducing travel speeds by narrowing travel lanes with buffers and center turn lanes designed to accommodate emergency vehicles. Space freed up by lane reductions makes room for walkers and bicyclists. Less traffic volume and lower speeds support more pleasant and productive places, places more like streets instead of highways or stroads. 

The main reason this project and others like it matter to the Strong Towns approach is that U.S. roadways, especially urban arterials and stroads—as Chuck Marohn explains in the Strong Towns book Confessions of a Recovering Engineer—are designed with speed and volume as the first two considerations. Safety and cost are the lowest priorities for most engineers. 

Strong Towns has repeatedly pointed out that most people in our communities would prefer to turn this list of priorities upside down. West Hartford residents answered a survey question during the road diet trial (1,900 respondents) with overwhelming support for the goal of safety over speed and volume:

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