Here’s a useful guide to understanding the benefits of a road diet:
https://safety.fhwa.dot.gov/road_diets/case_studies/roaddiet_cs.pdf
The introduction says:
ROAD DIET CASE STUDIES
Improving safety is a top priority for the U.S. Department of Transportation, and the Federal Highway Administration (FHWA) remains committed to reducing highway fatalities and serious injuries on our Nation’s roadways through the use of proven safety countermeasures, including Road Diets. Along with the development of the Road Diet Informational Guide, the FHWA Office of Safety commissioned a series of 24 case studies highlighting Road Diet implementations throughout the United States. The aim of this document is to provide State and local agencies and Tribal governments with examples and advice that can assist them in planning and implementing Road Diets in their own jurisdictions.
Many of the concepts described in this publication are illustrated in photographs and drawings. The drawings are for illustrative purposes only; they are not to scale and should not be used for design purposes. It is important to note that the lettering styles, arrows and symbols used in these case studies are not always consistent with those prescribed in the Manual on Uniform Traffic Control Devices (MUTCD). When employing treatments included in the case studies, only MUTCD-approved lettering styles, arrows and symbols should be used. Additionally, any highway agency wishing to implement a treatment that has not been included in the most recent edition of the MUTCD must request experimentation approval from the FHWA.
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