Benefits of MnROAD Research
In just over a decade of operations, MnROAD has provided a variety of important benefits to transportation agencies, the pavement industry, and the general public.
- Improving the national pavement design procedure: Data from MnROAD was used extensively in developing the new design procedure for the national highway system.
- Supporting better policy decisions: Data from MnROAD has impacted policy changes including seasonal load restrictions on Minnesota roads.
- New pavement evaluation equipment: MnROAD served as a proving ground for new types of equipment and tools to rapidly and effectively evaluate pavement engineering properties and performance.
- Effective environmental protection: Studies of pavement drainage and other environmental topics at MnROAD have helped protect wetlands and other environmental assets.
- Improving cold-climate performance: Research on cold-weather pavement cracking is contributing to the development of materials that stand up to the rigors of winter weather with reduced maintenance costs.
- Intelligent Transportation Systems: MnROAD’s Low-Volume Roadway has served as a testing ground for advanced driver-assistive systems incorporated into snowplows and emergency vehicles; these systems are now being used by plow operators in Minnesota and Alaska.
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Economic benefits
Research at MnROAD has contributed significant savings to the State of Minnesota. Conservative estimates based on Minnesota and national data indicate that MnROAD research has saved Minnesota taxpayers $33 million dollars per year. Transferring these savings to the national level offers the potential of $749 million annual savings.
MnROAD research implementation |
Minnesota savings $m |
National potential savings $m |
Spring load restriction policy |
14 |
210 |
Winter load increase policy |
7 |
105 |
Asphalt binder grading |
2 |
2 |
Low-temperature cracking reduction |
5.7 |
114 |
Mechanistic-empirical design (asphalt) |
2 |
100 |
Mechanistic-empirical design (concrete) |
1.2 |
60 |
Sealing pavement/shoulder joints |
1.2 |
60 |
New products and technologies
Research at MnROAD has contributed to the development or improvement of several products and technologies.
Dynamic Cone Penetrometer improvements
The Dynamic Cone Penetrometer is not a new tool, but its performance and applications have been extended through MnROAD research. Extensive use of the DCP at MnROAD led engineers to modify the apparatus in order to improve its usability and safety, and also to develop new applications for the DCP in evaluating pavement systems.
MnROAD engineers have made a series of physical modifications to the Dynamic Cone Penetrometer (DCP) itself—modifications that have now become standard on the DCP as used by Mn/DOT. These improvements make the tool quicker and easier to assemble, protect the user from injuries caused by misplaced hammer blows, and improve the durability of the DCP.
MnROAD’s DCP testing and the frequency of its testing gave it insight into the labor intensive and repetitive procedures needed to conduct the test properly. These insights contributed to the development of the Automated DCP (ADCP).
Much like the modifications made to the apparatus, investigations into the DCP’s penetration index were a product of MnROAD’s ongoing effort to characterize the pavement test sections for the sake of other research. This led to research correlating DCP measurements with soil modulus of elasticity. MnROAD’s continued work in refining the application of the DCP in the field prompted Mn/DOT to investigate and eventually adopt the use of the DCP to evaluate the uniformity of compaction of pavement edge drain trenches and granular base layers.
Ground Penetrating Radar
Though ground penetrating radar (GPR) has existed as a viable technology since the late 1970s, the pavement community did not completely embrace GPR in assessing pavements until the early 1990s. While many of these assessments were conducted on in-field pavements, very few were constructed on pavement systems whose design and components were documented to the extent of those at MnROAD. Hence, very soon after opening to traffic, GPR studies were conducted at MnROAD.
In the earliest work beginning in 1994, GPR was used to evaluate the thicknesses of the test sections and compare these values against known design thicknesses. The recommendation from this research was that GPR could be used confidently to assess the thicknesses of asphalt pavement systems and could be used confidently in conjunction with limited coring to assess concrete pavement thicknesses.
MnDOT has purchased and maintains state-of-the-art GPR equipment, including two data collection units and five antennas, capable of underground profiling from 2" to 50'. Currently, GPR calibration specifications are being developed (and possibly proposed as an ASTM standard) that incorporate this calibration information.
Intelligent Compaction
MnROAD’s commitment to the development of new products continues with an exciting new tool in pavement construction quality control, continuous compaction control (more commonly known as “intelligent compaction” or IC).Through demonstrations at MnROAD and the involvement of MnROAD engineers in a statewide IC Task Force, many factors related to the use of IC in unbound material compaction have been uncovered.
Overall, MnROAD engineers found that intelligent compactors do an excellent job of ensuring uniformity in compaction and acquiring the soil modulus for the next generation of mechanistic-empirical pavement design. Furthermore, MnROAD engineers have developed a series of steps needed to test for compaction in a given project in supplanting sand cone testing with IC. MnROAD experiences with IC have led to MnDOT’s implementation of IC for truck highway project construction and the drafting of pilot specifications for this use. In both instances, MnROAD engineers have played a role, either as a member of the statewide IC task force or in authoring or overseeing the specifications.