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The Colorado Department of Transportation has released this "how-to" on navigating the new diverging diamond alignment on the Fillmore bridge at I-25.
Courtesy of Colorado Department of Transportation

Will public have urge to diverge? Fillmore/I-25 switch to new traffic alignment now set March 25

       UPDATE, March 24: Because of weather, the date for traffic switch to a diverging diamond interchange, as described in the article below, has been changed to early March 25 (following overnight work starting tonight, March 24).

       Ready or not, here comes the new traffic pattern for the Fillmore/I-25 interchange project.
       An overnight “switchover alignment” by project contractor SEMA Construction is to start around 8 p.m. Wednesday, March 23, according to Ted Tjerandsen of Wilson & Co., project consultant for the Colorado Department of Transportation (CDOT).
       By 5 a.m. Thursday, March 24, Fillmore Street over the interstate will be reconfigured into what's called a diverging diamond interchange (DDI) layout.
       With the change, “I think we will see some traffic improvement,” Tjerandsen said.
       In the DDI, Fillmore Street drivers from either direction will find themselves
During the overnight demolition of a 17-foot-wide length of the old Fillmore Street bridge over I-25 last September, a girder and cross-member are pounded down. The machine, owned by demolition subcontractor Backhoe Services, is a 77,000-pound Caterpillar 330, using a 10,000-pound, hydraulic breaker attachment. Watching from the remaining 28-foot-wide length of the bridge are workers with Backhoe Services, the Colorado Department of Transportation and contractor SEMA Construction. Note the straight saw cut below the concrete barrier, which allowed the demolished length to be knocked away by the heavy machinery without damaging the retained length. The 28-foot-wide portion has continued to carry traffic throughout the winter, but is scheduled to be destroyed March 28-30. Taking over its traffic load will be the new north bridge, which was built after the demo above in the space where the 17-foot length had been.
Westside Pioneer file photo
switching sides as they travel over the interstate (see graphic on this page).
       The change will make Fillmore/I-25 one of a handful of interchanges in the United States to use the relatively new design, which traffic engineers believe is safer because it avoids the need for left-turn signals at on-ramps.
       Like dominos, the realignment is part of a series of construction events this month and April in which each result makes possible the next, with ultimate completion of the $15.1 million project tentatively expected in June.
       Leading up to the DDI switch over the past year has been the construction of two new bridges, about 30 feet apart. The most recent was the north bridge, which SEMA installed in December.
       The north bridge is not yet in service, as westbound Fillmore traffic has continued using the two-lane remainder of the original bridge (built around 1960), which sits between the two new structures.
       The word “remainder” is used because, in another operation last year, a 17-foot-wide length of the bridge's original 45-foot width was sawed/pounded off to make room for the new north bridge.
       The DDI “domino” will require Fillmore at the interchange, as well as its interstate ramps (but not the freeway itself), to be closed during the overnight work, which will be from about 8 p.m. March 23 to 5 a.m. or sooner March 24. Crews will use that time to restripe lanes as needed and activate stoplights at either end of the bridge, where the traffic diverges, Tjerandsen said. Also part of that work will be opening the north bridge to traffic and discontinuing use of the old bridge.
       The initial DDI traffic flow will be slightly different from the final version, mainly because of the need for worker space to build raised medians for the permanent alignment, he pointed out.
       But the median work can only happen after the “domino” of demolishing the old bridge. The demo is scheduled over three nights (March 28-30). It will require closures of the interstate and Fillmore in both directions (leaving the ramps open) each night from about 9 p.m. to 5 a.m., Tjerandsen said.
       After the DDI median installation is completed in subsequent weeks, SEMA will put in a final layer of pavement and permanent lane striping.
       Away from the bridges, ongoing work by SEMA involves lengthening and improving the southbound off-ramp and northbound on-ramp.

Westside Pioneer article
(Posted 3/17/16, updated 3/24/16; Transportation: (Fillmore/I-25)

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