City of Columbus, Ohio
The existing I-270 diamond interchange at Sawmill Road experienced heavy traffic congestion. To improve traffic flow, modification of the existing diamond or the creation of a single-point urban interchange (SPUI) alternative were evaluated. Burgess & Niple (B&N) recommended the SPUI, due to its superior operational characteristics. The new I-270 single-point urban interchange at Sawmill Road was the first SPUI in Ohio.
The SPUI combines two diamond ramp intersections into one large intersection over I-270 to simplify signalization. The SPUI provides superior operational characteristics due to the operation of simultaneous left-turn movements combined with the increased turning radii, allowing higher traffic saturation flows. Turning radii for left-turn movements are greater than 300 feet, which allows for a 30 mph design speed. An additional benefit is the reduction in the number of signalized intersections along Sawmill Road and an increase in distance from adjacent intersections. Improvements to the conventional interchange would have required widening of the structure and the addition of turn lanes to the ramps.
The SPUI at Sawmill Road included the construction of new approach ramps with dual left turn lanes, signalization of the intersection, and a bridge over I-270. The SPUI was part of a 4.3-mile $43 million segment of the I-270 outerbelt widening from four to eight lanes in northwest Franklin County to relieve congestion on the heavily traveled urban highway.
In 2001, the Consulting Engineers Council of Ohio (CECO) honored B&N with an Outstanding Achievement Award for the design of this project.