Keystone Parkway Corridor

Carmel, Indiana

This project was a fast-track design of a four-lane expressway, including grade-separated, full-access, roundabout interchanges at six existing intersections along one of the most heavily traveled roadways in the city of Carmel. The planning portion of the project evaluated the feasibility of lowering portions of existing Keystone Avenue and determined the effects the project would have on adjacent properties. American Structurepoint evaluated the use of modern roundabouts in various configurations for the interchanges in lieu of tight diamonds or single-point interchanges. Land acquisition services included right-of-way engineering and acquisition of 41 parcels for five separate construction contracts.

With the city of Carmel developing faster than it could keep up with its increasing traffic congestion, the community needed a time-saving and fiscally responsible alternative to knocking down residential homes and businesses to build a third lane of roadway in each direction along the heavily traveled Keystone Avenue.

Turning to American Structurepoint for its conceptual design and engineering expertise, the planning portion of the Keystone Parkway corridor project evaluated the feasibility of lowering portions of existing Keystone Avenue and creating elevated, grade-separated roundabouts at each of its six major existing intersections. American Structurepoint provided an innovative strategy for the City by developing five full-access, double-teardrop roundabout interchanges in lieu of traditional interchange configurations, including one complex interchange consisting of two teardrop roundabout intersections connected with a frontage road system.

Unlike any other corridor in the US, this solution minimized the interchange footprint and eliminated the need for signals, allowing for the free flow of traffic. The design not only lowered emissions and reduced idling, benefiting the environment, but it also improved the safety of the corridor. According to the city of Carmel, the redesign of the corridor's interchanges has reduced accidents with injury by 78 percent.

In addition, the more pedestrian- and bicycle-friendly transportation network has provided residents and visitors with easier access to merchants, parks, and recreational areas. Anticipating Carmel's continuing growth as a center for business, American Structurepoint also integrated architectural design details into the project, including specialty formlined walls, stamped concrete pavement, vertical stained concrete walls, decorative LED street lights, and ornamental railing. The design of the first two interchanges was completed in less than four months with construction having begun in April 2008 and opening to traffic in April 2009. Construction on the remaining interchanges was complete in the fall of 2010.