Home Road/Lewis Center Road Turbo Roundabout

Innovative turbo roundabout enhances safety and efficiency

Delaware County, one of Ohio's fastest-growing counties, has steadily improved its transportation network over the last decade. 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, initially recommending a hybrid 2x1 roundabout with right-turn bypass lanes. However, the design team proposed a turbo roundabout to better 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, 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 informs drivers which lane to enter ahead of the approach. A 3-inch tall, 2-foot-wide delineator curb deters lane changes but is mountable by trucks and emergency vehicles.

Opened in November 2023, the Home/Lewis Center Road roundabout is one of the few turbo roundabouts in the U.S. This project showcases the benefits of global roundabout design advancements for a safer and more efficient transportation network. Additionally, the roundabout requires less electrical power than a signalized intersection and reduces auto emissions due to decreased idling. It also incorporates elements such as salvaged pavement, low-maintenance landscaping, and LED lighting, contributing to its long-term sustainability.

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