In the eight years since the road diet for Madison was first proposed, research on road diets has evolved considerably. What was once a “slam dunk” case should now be re-considered.
Road diets don’t make roads safer, just less used. Initial research found that accidents dropped on roads put on road diet. This is true, but it is also true that drivers end up seeking to avoid the constricted roadway. When the decline in use is factored in, a large-scale study of road diets found no decrease in accidents/mile, meaning there is no real improvement in safety (Huang et al., 2002, Transportation Research Record). Meanwhile, traffic diverted to side streets may cause new safety problems, with one recent study finding “speeders outside the road diet area rose, with the percentage increases being fairly large, in the double digits” (Nixon et al., 2017, Mineta Transportation Institute).