Road Diets

“Road Diets” remove traffic lanes and replace with bike lanes. Typically a four-lane road is changed to two-lane with or without a center turn lane. Claims made are that collisions reduced 19% to 47%, however, these results lack supporting evidence in urban environments, since maximum results seen in rural areas, where actual collision rate was low. Use of percentages distorts the real benefit in actual numbers.

Despite the suggestion that road diets improve safety, according to the Federal Highway Administration:

  • Crash rates did not change significantly from the before period to the after period.
  • Road diet conversions did not affect crash severity.
  • Road diet conversions did not result in a significant change in crash types.

Additionally, they note that “There is a need for future safety and operational studies, under a range of traffic volumes and other conditions, to help identify the situations where road diets would be appropriate. In addition, traffic operations and capacity must be considered fully at a given site before implementing road diets and other lane reduction measures.”

They also indicate that road diets are not suitable for roads with average daily traffic above 20,000 vehicles because “for road diets with ADTs above approximately 20,000 vehicles, there is a greater likelihood that traffic congestion will increase to the point of diverting traffic to alternate routes.”

Positive Results

  • Provide a dedicated lane for cyclists

Negative Results

  • Do not improve bike incidents at intersections
  • Do not improve bike incidents at left turns
  • Do not improve bike incidents in business areas where parked traffic backs out
  • Increases rear-end collisions for vehicles
  • Increases road range – several have been backed out: