December 13, 2013
Intersection and Interchange Geometrics
Through Every Day Counts, the Federal Highway Administration is promoting intersection and interchange geometrics, proven techniques to improve intersection safety and boost the efficiency of moving traffic. These innovative designs include diverging diamond interchanges, displaced left turn intersections, U-turn intersections and roundabouts.
The diverging diamond interchange eliminates the signalized left-turn phase at the interchange's two intersections by shifting traffic to the left side of the road between the ramp terminals. This enhances safety by reducing the number of traffic conflict points and improves traffic flow by decreasing the number of signal phases.
Georgia's first DDI—on Ashford Dunwoody Road over I-285 near Atlanta—has improved travel times through the congested area since it opened in 2012. In its first year of operation, 20 percent fewer crashes occurred near the interchange.
A public information campaign, including a "Can You DDI?" website, educated drivers about the new interchange design. The video below shows how the Ashford Dunwoody Road DDI operates.
Florida Saves With Alternative Technical Concepts
Using alternative technical concepts is saving the Florida Department of Transportation about $30 million on an I-95 design-build project. The agency originally proposed a modified diamond interchange that included a third-level interchange with two curved steel flyover ramps. Several firms that replied to the request for proposals offered ideas for cost-saving alternatives. The winning proposal suggested an at-grade Texas U-turn alternative that eliminated the use of the curved steel flyover ramp concept, saving millions and providing an equal or better level of service compared to the original concept.
Michigan Finishes Bridge Project Early
Using innovative traffic management and the construction manager/general contractor process enabled the Michigan Department of Transportation to reopen all lanes of the Zilwaukee Bridge on I-75 three weeks early. The $70 million project includes reconstructing four miles of I-75 and replacing the bearing pads on the bridge to extend the structure's service life and make the ride smoother for drivers. The agency accelerated the first section of the project, focusing on the southbound lanes, to avoid construction during winter weather. Work on the northbound lanes is scheduled for 2014. A video highlighting the project's early completion is available here.
National Park Service Considers Roundabout
National Park Service staff met with the Colorado Department of Transportation and FHWA to learn about building a roundabout in a mountain community. Grand Teton National Park officials are considering a roundabout on a section of Highway 89 that runs through the Wyoming park. The Colorado DOT is building a roundabout on I-70 in Eagle and recently finished one in Edwards. Roads stayed open to traffic during both projects. The Colorado DOT is using the construction manager/general contractor project delivery method on the Eagle project to streamline construction staging.
EDC Exchange Now Online
A recording of FHWA's EDC Exchange on "Locally Administered Federal-Aid Projects: What's In It for You?" is available online for those who couldn't participate in the live session. The webinar provides an overview of locally administered Federal-Aid projects, plus details on stakeholder partnering, certification programs and consultant services flexibilities. It ends with a question-and-answer session. Recordings of other EDC Exchanges on topics such as traffic incident management responder training and accelerated bridge construction are also online.