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

Oklahoma's first DDI

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

Drivers should be aware of the new traffic configuration at the I-40 and SH-6/Main St. interchange in Elk City with the opening of the state's first Diverging Diamond Interchange:

SH-6 traffic is now in its final DDI configuration. Drivers should use caution as they enter the reconfigured interchange for the first few times.

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.

This area remains an active construction zone through winter 2020. Motorists are urged to use caution as traffic adjusts to the new configuration.

Drivers on I-40 lanes and ramps as well as SH-6 lanes may experience intermittent closures as final work continues. The project is set to complete in winter 2020.

Drivers should begin thinking about how to safely navigate the DDI. 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.

In 2015, 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, ODOT began a project to demolish the existing SH-6 bridges over I-40 and replace them with a new type of interchange - a Diverging Diamond Interchange.

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

Watch: See what I-40 and SH-6 will look like once the DDI is 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-40 and SH-6. The last survey completed in 2017 shows 8,500 vehicles 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 a proven solution for improving traffic flow and safety at the interchange.

Reconstruct SH-6 and 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-freeway road cross to the opposite sides of the bridge at the freeway.

Currently, there are just under 100 DDIs nationwide.

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-hand turns from all directions.

Wrong way entry to ramps become extremely difficult.

Traffic Impact During the Project

I-40 and SH-6 will 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-40 and 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: