Quite simply "a road diet is anytime you take any lane out of a road" say traffic-calming expert Dan Burden in a recent video shot with Streetfilms.

A road diet is generally described as "removing travel lanes from a roadway and utilizing the space for other uses and travel modes" according to Federal Highway Administration's Road Diet Informational Guide. The most common road diet lane reconfiguration is the conversion of an undivided four lane roadway to a three-lane undivided roadway made up of two through lanes and a center two-way left-turn lane (TWLTL). The reduction of lanes allows the roadway to be reallocated for other uses such as (protected) bike lanes, pedestrian refuge islands, transit uses and/or parking.

The first time people hear about a road diet, their initial reaction likely goes something like this: "How can removing lanes improve my neighborhood and not cause traffic backups?" It seems counterintuitive, but taking away lanes can actually help traffic flow smoother while improving safety for everyone.

And here's something to keep in mind during this era of lean budgets: road diets are a highly-effective infrastructure improvement that can be implemented quickly and at low cost.

Historically, road diets have been shown to enhance safety and access for all users, forming a welcome environment for various transportation modes and creating more livable spaces. According to the Federal Highway Administration (FHWA), road diets typically reduce collisions by 19 to 47 percent.

They reduce speeding and make vehicle movements more predictable while shortening crossing distances, usually through curb extensions or center median islands.

They're good for cyclists: Many road diets shift space from car lanes to create bike lanes.

They're good for drivers: Less speeding improves safety for motorists and passengers, and providing left-turn pockets allows through traffic to proceed without shifting lanes or waiting behind turning vehicles.

Road diets have been done on roadways across the U.S. that carry nearly twice the traffic volumes, up to an average daily traffic (ADT) of 23,000 vehicles per day (vpd), as College Drive (10,558 ADT) and East 8th Avenue (13,629 ADT) in Durango. They have been found to be more successful than the previously existing conditions in terms of improving business visibility and access, improving left-turn capabilities, maintaining and, in cases, improving traffic flow, reducing rear-end and sideswipe crashes, and improving bicycling conditions and safety, among other benefits.

The traffic study (PDF) in 2016 showed that level of service on the roadways will maintain an acceptable level of service (projected out to 2030) with a lane reduction. This means that traffic can flow at current levels even with a road diet. The road diet project will provide the opportunity to implement necessary pedestrian crossing enhancements to improve access across East 8th Avenue at 3rd Street (Horse Gulch Medical Campus) and along College Drive, and improve overall safety for all road users. Moreover, the project was identified in the 2012 and 2016 Multimodal Transportation Plan and as such moved towards project implementation in the 2017 budget cycle.

The recommendations from the City of Durango's Traffic Study align with FHWA conclusions as the safety study suggests that 24 percent of the total traffic collisions during the study period are preventable by a road diet.

Yes.

1. West Mulberry Street Improvements and Pilot Project in Fort Collins, Colorado. The Mulberry St project was implemented in summer 2018. Since that time, preliminary travel times have been collected (attached) that demonstrate travel times on Mulberry from College to Shields are about the same or even reduced 10-15 seconds during peak traffic. The worst case for traffic in the study shows travel times increasing 20-25 seconds during the peak traffic.
2. Division Avenue Road Diet in Grand Rapids, Michigan. The results include decreased vehicle speeds (-1 to -4 mph), decreased traffic volumes (-18% to -29% north of Wealthy Street) and increased parking. After the Division Avenue Road Diet installation, the City of Grand Rapids reported that businesses along the corridor are generally happy with the project because of the perceived improvement in the quality of life attributes and livability of the community.