Home Road/Lewis Center Road Turbo Roundabout

Innovative turbo roundabout provides greater safety and efficiency

Delaware County is one of the fastest-growing counties in Ohio and has steadily improved its transportation network over the last decade to meet development demands. As part of a phased expansion, the Delaware County Engineer’s Office engaged OHM Advisors to design a 1.5-mile extension of its primary east-west corridor, Home Road, from US-23 to Lewis Center Road.

A traffic analysis projected high volumes of southbound left turns from Lewis Center Road to the Home Road extension, recommending a hybrid 2x1 roundabout with right-turn bypass lanes. However, the design team suggested a turbo roundabout to handle the projected traffic volume. Developed in the Netherlands, turbo roundabouts use spiraled geometry and raised lane dividers to discourage lane changes within the circulatory roadway, thereby reducing conflict points that often result in minor crashes in traditional multi-lane roundabouts.

The design for this project is a modified-knee turbo roundabout with only an inside left turn lane on one approach to manage the high volume of southbound left turns and reduce congestion. To aid drivers in navigating the roundabout, the curved entry is consistent with other roundabouts in Delaware County, and signage tells drivers which lane to enter ahead of the approach. A 3-inch tall, 2-foot-wide delineator curb deters lane changes but is still mountable by trucks and emergency vehicles traveling through the roundabout.

One of the few turbo roundabouts in the U.S., the Home/Lewis Center Road roundabout opened in November 2023, enhancing connectivity for residential neighborhoods and commercial development in Delaware County while exemplifying the benefits of global roundabout design advancements for a safer and more efficient transportation network. In addition to requiring less electrical power than a signalized intersection and reducing auto emissions due to decreased idling, this roundabout also incorporates elements such as salvaged pavement, low-maintenance landscaping, and LED lighting that add to its long-term sustainability.

Project Highlights: turbo roundabout, survey and existing right-of-way resolution, roadway design, drainage design, traffic control and maintenance of traffic design, lighting and landscape design, utility coordination, right-of-way plan preparation, and public involvement exhibit preparation.