New, cheaper interstate bridge design key to grant request for Fillmore/I-25

       Once known as “Little London,” Colorado Springs is supporting a grant that would - for the sake of improved traffic flow - redo the top of the Fillmore/I-25 bridge so that motorists would drive on it like Britishers.
       “I know it sounds crazy,” commented Kathleen Krager, a city transportation engineer, on the proposed “diverging diamond interchange” (DDI) design that would direct through traffic to the left side of the bridge. But she pointed out that the relatively new design - only used on the interstate system since 2009 - would eliminate the need for left-turn lanes on the bridge.

A 2009 aerial view shows the nation's first diverging diamond intersction, over I-44 in Springfield, Mo. The bridge traffic is directed to the left, eliminating the need for left-turn lanes. The bridge layout is like Fillmore/I-25 in that the street bridge goes over the interstate and there are no "cloverleaf"-type ramps.
Courtesy of Colorado Springs Traffic Engineering

       One of the problems on the Fillmore bridge now is vehicles in the left-turn lanes backing up into through traffic, Krager said.
       Another big plus with DDI, as local governments see it, is greatly reduced costs. A full interchange replacement at Fillmore/I-25 was priced at $84 million four years ago, based on a previous environmental assessment (EA) developed by the Colorado Department of Transportation (CDOT). If the requested grant ($10 million from federal stimulus funds) is approved, regional officials believe that will pay for all the DDI work, as well as improvements to the interchange's southbound off-ramp and northbound on-ramp.
       The bridge itself, built about 50 years ago, is solid and does not need replacement, Krager replied, in answer to a question.
       As recently as last fall, the Fillmore interchange was a relatively low transportation priority in the Pikes Peak region. The EA had called for putting in a wider interchange - with traditional left-turn lanes - to handle higher traffic volumes; however, the area has other transportation needs and Fillmore wasn't even seen as the worst interchange. The Pikes Peak Area Council of Governments (PPACG) board, consisting of representatives from governments in El Paso, Park and Teller counties, had been focusing in the past year on the deficiencies at Cimarron/I-25.
       What changed matters was a visit from U.S. Secretary of Transportation Ray LaHood the day before the PPACG board's monthly meeting. In the past, when applying for stimulus money, regional officials have proposed several project possibilities. According to Sallie Clark, PPACG board chair, LaHood “stated that we need to come together as a region and select a focused project to be successful with limited dollars.”
       Seeking to follow that direction, the board chose Fillmore, as the most “shovel-ready” (no additional right of way needing to be purchased) and affordable. Also working in its favor is a neighboring Pikes Peak Rural Transportation Authority project, slated to break ground later this year, which will realign Chestnut Street away from the interchange. That project not only makes a DDI layout possible (by reducing the stoplight responsibility on the west end of the bridge from six “legs” to four), but the Chestnut project's $7.1 million expense can be used as a “match” for the federal funds, Krager pointed out.
       After the PPACG board vote, the State Transportation Advisory Commission unanimously recommended to the Transportation Commission Feb. 10 that CDOT submit Fillmore/I-25 as one of its two projects for the state as a whole.
       The grant application deadline is mid-March. “We'll know by early summer” if the grant has been approved, she said. If so, CDOT will coordinate the project, with construction to begin by spring 2013.
       The official name of the federal grant program is Transportation Investment Generating Economic Recovery (TIGER). Because this is TIGER's fourth year, the 2012 program is called TIGER IV. The program is part of the American Recovery and Reinvestment Act of 2009, which created what's sometimes called the “stimulus package.”
       The first DDI interchange on the U.S. interstate system was opened in June 2009 on I-44 in Springfield, Mo. It is now one of three in the country, Krager said.

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