City of Manhattan

K-18/K-113 Diverging Diamond Interchange

Manhattan, KS

The K-18/K-113 Diverging Diamond Interchange (DDI) project came about as a response to increasing traffic congestion and safety concerns in and around the interchange which serves as a significant transportation hub for the City of Manhattan and Riley County, through which thousands of cars pass each day. In the previous configuration, left turn movement for southbound traffic on K-113 to the on-ramp for eastbound K-18 experienced significant congestion during the peak traffic conditions.

Benesch provided Value Planning, phased interchange reconfiguration design and construction phase services to assist the City of Manhattan and the Kansas Department of Transportation. This approach enabled them to meet the additional challenges of tight budgets, physical constraints and confined construction schedules while improving the functionality and safety of the interchange.

The use of VP/VE methodologies is still relatively unique on local transportation projects which do not have federally mandated reviews. This process produced a design that adjusted the roadway profile and alignment of the under route (K-113) along with tailoring the DDI configuration. The design circumvented the need to remove and rebuild the bridges, producing considerable cost savings. Beyond salvaging the bridges, existing pavement was reused wherever possible to achieve sustainability objectives and control costs.

Construction phasing in multiple stages played an important role in meeting the need to maintain traffic throughout construction.

Now complete and fully operational, the DDI facilitates efficient traffic through protection of left turn movements and reduced queues along both the K-18 and K-113 corridors. VISSIM was used to analyze the DDI geometrics to confirm the number of lanes required to handle 20-Year traffic volumes.

Project highlights

  • Value Planning/Value Engineering process and alternative evaluation
  • Retrofitted Diverging Diamond Interchange (DDI) design
  • Highly involved public involvement
  • Extensive traffic analysis
  • Multi-stage construction phasing
  • Re-use of existing materials