Current I-40/I-240 intersection with cloverleaves and one-lane exit ramps cause massive traffic jams.

Buchart-Horn's overall design of the I-40/I-240 Interchange indicates the exclusion of single lane ramps and the addition of tri-level flyover ramps. Please click on the images above to see a larger version in a new window.

Generating traffic jams and rush hour adventures, twenty-one lanes of interstate highway move through the point where Interstate 40 meets the Memphis Bypass (I-240). Some pathways through this maze are low-speed "cloverleaf" connections. In addition, as Interstate-40 brings in five lanes of traffic from Nashville, the roadway squeezes drivers into a dwindling number of lanes.

During morning rush hour, these highway limitations become painfully clear, as east side traffic jams build for miles along the bypass and the road from Nashville. In afternoon rush hour, everything backs up again, but in the opposite directions. At most times, motorists who know the area feel relief after navigating through it.

So the Tennessee Department of Transportation (TDOT) began planning for major upgrades at the I-40/240 junction. With their sights on improved safety and traffic flow, designers looked at large flyover structures that could accommodate modern highway speeds and rush hour vehicle volume.

Citizen response was positive during a public hearing in October '98, even though the new interchange requires the relocation of one business and several homes.

Buchart-Horn, Inc. began preliminary design based on a study for the entire I-240/I-40 corridor in 1997 utilizing metric measurements mandated by the Federal Highway Administration (FHWA). While other metric-based highway projects had been undertaken in Tennessee, design of the four-level direct connection interchange involved large bridges and structures, making it the first metric project of its size and kind within the state.

But in early July 1998, the FHWA responding to inquiries on the impact of metric conversion related to the Transportation Equity Act for the 21st Century (TEA-21), told states that the metric conversion would be optional. At the same time, contractors who were unaccustomed to larger metric projects indicated the metric planning could lead to construction costs as much as ten percent higher.

So in 1999, engineers from Buchart-Horn, Inc.'s Memphis Office began converting preliminary metric documents into English equivalents as they developed right-of-way plans for the expanded interchange that promises to mitigate some of the worst rush-hour jams in that beautiful city along the Mississippi River.

Ultimate design involves three flyover ramps and six through lanes to accommodate up to ten thousand vehicles per hour. Right of Way plans will be completed by August. TDOT wants final design by the end of the year so the project can go to bid early in 2000.

"That's a tight schedule for a four or five mile-long design," said Buchart-Horn's Project Manager, "but our team enjoys the challenge and we'll have it completed."

While one design team works on right-of-way plans, the transportation division has completed preliminary bridge design for all phases of the project, and is well into final design for the eleven spans needed for Phase 1 of the new interchange.

Phase 1 of the $60 million project includes construction of a third level of flyover ramps over both interstates to merge traffic heading toward the south loop of I-240.

Like the Austin Peay project that Buchart-Horn designed in 1996, the expanded I-40/240 interchange is complicated by its proximity to the New Madrid Fault, an area of seismic activity that puts the spans in Risk Zone 3. That dictates structural design for seismic category "C," meaning they require nearly the same seismic design criteria that would be needed in San Francisco.

In addition, Tennessee is a leader in integral abutments and elimination of deck joints. Eliminating the joints reduces future maintenance and structural deterioration from water infiltration.

"So seismic and thermal issues complicate the design," said a B-H Associate Vice President, "We're designing for seismic protection and designing without expansion joints. To accommodate the thermal and seismic design requirements, we've employed a pier cap system that is an integral part of the bridge superstructure. That design distributes the seismic and thermal loads between the integrated superstructure and substructure."

The project site is one of the busiest highway intersections in Tennessee, so construction phasing will be a big part of final design. In addition to higher-speed exit ramps, the new design provides enough lanes to eliminate the current bottleneck where five lanes of traffic have to merge into two through lanes and two exit lanes. Flyover connections and multiple levels of roadway will improve safety as well as rush hour traffic flow through this major intersection on the east side of Memphis.