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Single Point Urban Interchange at I-270/Sawmill Road

As part of the North Outerbelt Widening (NOW) Project, the Interstate 270 at Sawmill Road diamond interchange was reconstructed. The existing diamond was experiencing heavy traffic congestion, which was also affecting drivers on I-270. With the proposed widening of I-270, it was anticipated that problems associated with the interchange would increase significantly. The ADT on I-270 was projected to increase from 94,000 in 2000 to 122,000 in 2020 and on Sawmill Road from 41,000 to 63,000. To address these issues, an evaluation was conducted of alternatives, considering the modification of the existing diamond or the creation of a single-point urban interchange (SPUI). The regional importance of this interchange required that any impacts resulting from construction of a new facility be minimized. As a result, Burgess & Niple recommended the SPUI because of its superior operational characteristics and minimized construction impacts. The I-270 SPUI at Sawmill Road opened for traffic in August 2000, and it is the first SPUI in Ohio.

The SPUI simplifies signalization by bringing all left-turning traffic and thru traffic to one signalized intersection, as opposed to the two signalized intersections used by a conventional diamond. The SPUI uses only three main phases to control traffic, increasing operational efficiency. The SPUI's superior operating characteristics, combined with the increased turning radii and free-flow right-turn movements, allow higher traffic saturation flows. Turning radii for left-turn movements are greater than 100 meters, which allows for a 50 km/hr design speed. An additional design benefit is the reduction in the number of signalized intersections along Sawmill Road and an increase in the distance from adjacent intersections.

The SPUI at Sawmill Road includes a complete reconstruction of the interchange area, signalization of the intersection, and a bridge over I-270. The estimated construction cost of the SPUI is $6.8 million and is part of a 4.3 mile, $36 million widening of the I-270 outerbelt designed by Burgess & Niple.

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