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Elk City's Diverging Diamond Interchange at I-40 & SH-6

Oklahoma's first DDI

Celebrating Interchange Innovation at I-40 and SH-6 in Elk City from ODOT on Vimeo.

I-40 and SH-6 Interchange in Elk City OPEN in final DDI configuration marking a state first

Drivers will experience a new traffic configuration in Oklahoma at the I-40 and SH-6/Main St. interchange in Elk City with the implementation of the state's first Diverging Diamond Interchange:

  • SH-6 traffic has beenn its final DDI configuration since late summer 2020. Drivers should use caution as they enter the reconfigured interchange for the first time.
  • Motorists need to pay additional attention to all traffic control devices, including the new traffic signals, pavement markings and signage as well as follow the speed limit.
  • Motorists are urged to use caution as traffic adjusts to the new configuration.

Drivers should think about how to safely navigate the DDI before they drive it. Here are several safety tips to consider before driving through the new interchange:

  • As you approach the interchange, drive for the conditions by following the speed limit. Pay attention to traffic control devices and pavement markings.
  • As you enter the interchange, follow the signs, signals and pavement markings to cross through the intersection at the first set of traffic lights. Traffic will appear as if on a one-way street as it crosses above I-40.
  • Vehicles continuing straight on SH-6 after crossing I-40 simply proceed through a second set of traffic lights.
  • All left turns onto the interstate are free flow, meaning vehicles do not have to stop to access the ramp.

In2015, the existing twin bridges on SH-6 over I-40 were deemed structurally deficient, meaning the roadway is safe for travel but in dire need of repair. Starting in May 2019, ODOTbegan a project todemolish the existin gSH-6 bridges over I-40 and replace them with a new type of interchange – a Diverging Diamond Interchange.

Watch: A step-by-stepvideo of how to use a Diverging Diamond Interchange

Watch: See what I-40and SH-6 will look like once the DDIis completed

Courtesy: CEC Corporation

(Edit: Plans are to also place stop lights on the ramps.)

Elk City is a growing community. Sitting along the famous "Mother Road" Route 66, the town experiences high traffic volumes on both I-40and SH-6. The last survey completed in 2017shows 8,500vehicles travel SH-6 on average per day.

About the Project

Construction of Oklahoma's first Diverging Diamond Interchange began in May 2019 at I-40 and SH-6 in Elk City. The innovative design offers aprovensolution for improving traffic flow and safety at the interchange.

  • Reconstruct SH-6and I-40 on-and-off-ramps.
  • Construction is estimated to cost $16 million.
  • Construction is expected to last about a year, with a substantial completion date of summer 2020, weather permitting.

About Diverging Diamond Interchanges

The definition of a Diverging Diamond Interchange: Two directions of traffic on the non-freewayroad cross to the opposite sides of the bridge at the freeway.

  • Currently, there are just under 100DDIsnationwide.
  • The first was constructed in Springfield, MO in 2009.
  • DDIs create safer, less congested intersections.
  • DDIs allow for fewer conflict (accident) points.
  • DDIs give drivers better sight distance at turns.
  • DDIs pedestrian crossings are shorter.
  • DDIs aim to eliminate the left turn and thereby increase safety
  • DDIs give "free-flowing" or simple left and right-handturns from all directions.
  • Wrong way entry to ramps become extremely difficult.

Traffic Impact During the Project

  • I-40 and SH-6will remain open to the traveling public.
  • I-40 will be narrowed to one lane in each direction at times throughout the project.
  • I-40 will have minimal ramp closures at SH-6.
  • Crews will have minimal nighttime closures of I-40and SH-6 to demolish the existing bridges.

Stay updated

During the project, drivers should use the following sources to stay connected about changing traffic conditions:

  • ODOT's traffic advisories at
  • ODOT's Twitter and Facebookaccounts
  • ODOT's app on the Apple and Android App Stores
Last Modified on Jun 14, 2023
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