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INDOT has implemented innovative, creative, and fiscally responsible solutions to get the most from every dollar spent while enhancing safety and improving Indiana’s transportation infrastructure. INDOT continues to find, explore and develop new ways to plan, finance and construct Indiana’s world-class transportation systems.
A technologically innovative construction method will save time and millions of dollars during construction of a new U.S. 421 bridge over the Ohio River between Milton, Ky., and Madison, Ind. Using a method called “truss sliding,” a new 40-foot wide, 3,181-foot-long truss will be moved along steel rails and plates and “slide” into place atop the existing piers, which will be rehabilitated. At just 20 feet wide, the original Milton-Madison steel truss bridge is too narrow for modern traffic. Because of the innovative construction method, the bridge will close for a total of only 10 days during construction, rather than the originally 365-day closure. U.S. Secretary of Transportation Ray LaHood, former Indiana Gov. Mitch Daniels and Kentucky Gov. Steve Beshear broke ground on the project in November, 2010. The low bid submitted by Walsh Construction Company of LaPorte, Ind., for $103 million, was 20 percent below the original $131 million construction estimate. The first Milton-Madison steel truss bridge opened in 1929.
Beginning in 2011, INDOT is incorporating safety edge, a pavement design that includes an edge treatment for asphalt and concrete roads that improves roadway and traffic safety, into its construction specifications. Two-lane rural highways often have unpaved shoulders immediately adjacent to the paved roadway. If roadway maintenance does not keep material against the pavement edge, a pavement-shoulder drop-off may form. Drop-off heights can vary from less than an inch to six inches or more. When a vehicle leaves the paved roadway and encounters a pavement-shoulder drop-off, it may be difficult for the driver to steer the vehicle safely back onto the roadway. The side of the tire may scrub along the drop-off, resisting the driver’s attempts to steer and make a smooth reentry to the roadway. This resistance often leads to a driver’s over-correcting, which may slingshot vehicles across the road, resulting in loss of control or serious traffic accidents. With safety edge, the pavement edge is formed at a sloped angle to lessen the resistance of a tire to remounting the drop-off. The lessened resistance allows vehicles a more controlled reentry onto the roadway. INDOT design specifications have been modified to incorporate safety edge in appropriate projects. INDOT is one of the first state departments of transportation to incorporate safety edge into its design specifications.
INDOT is working on its second quality control/quality assurance soils project using intelligent compaction. The project involves the US31/US 35 interchange, which is part of the US 31 Kokomo Bypass. Embankment contractor Fox Construction is using rollers equipped with sensors (accelerometers) that can determine the relative stiffness of the soil to map the embankment as it is constructed. The rollers also use Global Positioning System technology that can determine the coverage of the rollers over the embankment area. In 2010, INDOT used intelligent compaction on the SR 25 Hoosier Heartland project, making Indiana a leader among states in implementing this new technology that enhances long-lasting pavement performance. Intelligent compaction technology has been featured by the Federal Highway Administration on its Every Day Counts Initiative website, which highlights innovative technologies and processes that shorten project delivery, enhance the safety of the nation’s roadways, reduce costs, and protect the environment.
Alternate Bidding Process
INDOT’s traditional bidding method — in which INDOT developed plans and determined specifications, then selected the lowest bidder — left contractors with little room for offering alternative solutions or bidding based on what’s most economical. INDOT modified its bidding to encourage alternatives for selected projects. Among those modifications are:
INDOT has implemented a design change that will save more than $1.2 million each year in concrete roadbed repair costs by reducing the cost and improving the performance of concrete pavement. In the past, concrete slabs occasionally curled and warped after installation due to temperature variations. This curling impacts pavement performance and leads to premature mid-slab cracking. Conventional design solutions to this problem called for the installation of thicker pavement to reduce mid-slab cracks. Following a research project, INDOT and Purdue University’s Joint Transportation Research Program (JTRP) discovered that shorter joint spacing can be used to reduce stresses in concrete slabs and prevent the occurrence of transverse cracks. Reducing slab joint spacing resolves curling and premature cracking, allowing for a reduction in thickness of the concrete roadbed. This solution reduced roadbed construction and repair costs by $1.2 million in 2011 and is projected to save more than $2.4 million over the next three years.
INDOT engineers use nuclear gauges to perform soil compaction tests to measure soil density and water content, the primary criteria in determining soil compaction quality. These devices, however, are considered hazardous as they emit a beam of radiation particles. As a result, nuclear gauges require licensing, regulatory permitting and considerable training when used to measure soil density. For these reasons, INDOT funded a project with the JTRP at Purdue University to evaluate options to replace nuclear gauges. Test results with the Dynamic Cone Penetration Test (DCPT) demonstrated that the DCPT was effective in measuring density and water content of soils and could replace nuclear density gauges in soil compaction. Furthermore, the DCPT was found to be faster, easier to operate, and able to take deeper measurements than nuclear density gauges. As a result, a Recurring Special Provision using the DCPT for soil compaction quality control was developed and is now used on INDOT construction projects. INDOT conducted more than 8,000 density tests in 2011. Projected annual savings for using DCPT as a tool for soil compaction quality control rather than the nuclear testing equipment is $480,000 annually.
Edward E. Pollack
Director-Innovation and Enhancement
Indiana Department of Transportation
100 N. Senate Ave., IGCN755
Indianapolis, IN 46204
Barry K. Partridge, Ph.D, P.E.
Director-Research & Development
1205 Montgomery Street
P.O. Box 2279
West Lafayette, IN 47906-2279