The Rationale for Roundabouts: How they can play a critical role in rural traffic safety programs

Roundabouts are a polarizing topic for communities and are often the ire of residents and motorists, but they are a practical and effective solution for mitigating traffic incidents and fatal crashes.

In the United States, over half of crashes occur at intersections. Roundabouts are an effective tool for removing conflict points that traditional stop-controlled or signaled intersections retain and have been proven to reduce crashes by over 35% and injury crashes by over 70%.

Located in the heart of New York’s Finger Lakes region, Ontario County’s roadways are similar to many across the state, with rolling terrain, rural-to-suburban settings, a 55-mph speed limit, and hundreds of 3- and 4-leg stop-controlled intersections. Through a careful review of traffic data, County officials uncovered that 50% of vehicle-related fatalities were occurring on rural roads. Driven by this concerning statistic, officials established a countywide traffic safety program with a focus on intersection improvement, taking a methodical and data-driven approach in line with National Highway Safety standards.

One intersection identified for improvement was the four leg, two-way stop-controlled intersection at County Route 28 and Shortsville Road in the Town of Farmington. The intersection had a crash rate roughly six times higher than the statewide average, and in the years leading up to the redesign was the scene of dozens of serious crashes, including two high-profile fatalities.

Ontario County Public Works contracted with Bergmann’s team of highway engineers, traffic engineers and landscape architects in fall 2018 to lead the transformation of this intersection. Collaborating with stakeholders to develop a modern roundabout, the Team considered a number of key design factors, including:

1. Appropriate geometric design to gradually decrease driver approach speeds
2. A durable, cost-effective pavement material, utilizing concrete instead of asphalt
3. Central island landscaping designed for both aesthetics and functionality
4. Lighting levels that illuminate the roundabout for driver safety while reducing glare for immediate neighbors

The intersection reopened in October 2020 and in the 18 months following, traffic incidents have decreased 30%, without any injury-inducing or fatal crashes. The success of this and other redesigns across the county have drawn praise from residents, county and town officials and emergency responders. At the ceremonial ribbon cutting, Shortsville Fire Chief Jason Wagner, who frequently responded to crashes at the intersection, shared his appreciation for local, county and state officials who listened to pleas for a solution and for making the investment so “hopefully I never have to come here again.”

CR 28 and Shortsville Road was the third roundabout redesign Bergmann completed for Ontario County. The fifth entered design in the winter of 2021.

What makes roundabouts a successful design solution for rural intersections? Roundabouts check off four critical boxes, including reducing speed, which is often a top priority for rural communities:

1. Roundabouts are a geometric intervention. They are designed so drivers negotiate the intersection at speeds in the range of 15-25 mph, regardless of the speed limits on the approaches.
   1. Crashes at Ontario County’s rural intersections involve high speeds, which tend to result in severe injuries or fatalities.
2. Roundabouts require vehicles to yield on entry and navigate around the raised, circular island; therefore, the possibility of a right-angle crash is substantially reduced. Crashes that occur do so at more acute angles and lower speed.
   1. In rural environments, it is not uncommon for drivers to miss a stop sign or traffic signal, resulting in a right-angle crash. Signals and all-way stop control intersections rely on driver obedience. Signals and all-way stop control may elevate the potential for high-speed, rear-end collisions.
3. Roundabouts eliminate the need to turn left or cross conflicting traffic. Entering vehicles yield to traffic already in the circle and proceed when there is a safe gap. Gaps are easier to judge at lower speeds and in one direction only.
   1. It can be difficult for a driver turning left or crossing the major road to properly assess the speed of approaching vehicles, resulting in mistakes and potentially severe crashes.
4. Roundabouts with four approaches result in 8 possible points of vehicular conflict.
   1. Traditional four-way intersections have 32 possible points of vehicular conflict.