Safety Improvements – NH Route 128 and Route 171 Intersection

NH Route 28 is a vital regional arterial highway traversing the Lakes Region of New Hampshire. Its intersection with NH Route 171 has a history of severe crashes prompting the town of Ossipee and the NHDOT to take action. A roundabout design was the chosen solution for the intersection for the safety and operational benefits that it would provide. Funding was through the Highway Safety Improvement Program.

GM2 Associates Inc. was the prime engineering consultant, providing preliminary and final design services, permitting and public outreach support, as well as right of way (ROW) delineation and registry plan development for the NH Route 28/171 roundabout design. The scope involved the design of a single lane roundabout centered on the existing intersection along with approximately 1,600 feet of roadway reconstruction on Route 28 and 400 feet on Route 171. In addition, GM2 coordinated with Carroll County to design waterline relocations for the existing facilities within the intersection. A closed drainage system along with a stormwater treatment swale were also incorporated into the project’s design.

The project was developed from study phase to construction documents in nine months and advertised on schedule in April 2019. The roundabout was operational by the end of 2019 and finalized in July 2020. Unique techniques employed included a streamlined scope of work, engagement of owner’s district resources for advance tree removal, design modifications eliminating lengthy permitting timelines, and no permanent property acquisitions. All needs were accomplished by providing a safer intersection and on-time on-budget project delivery.