This project represented the initial attempt to develop an automated procedure to use traffic flow data rather than snowplow driver observations to determine when roads are clear enough to stop plowing after a snow event. This procedure could provide service at reduced costs by deploying snowplows more efficiently. While promising, the procedure is not yet ready for wide deployment.
Researchers evaluated and compared the laboratory and field performance of recycled asphalt pavement and fractionated RAP by monitoring test cells at the MnROAD facility between 2008 and 2012. After four years of data collection, extracted binders met or exceeded expected performance, and all cells were performing very well and differed little in performance. Researchers will continue to monitor MnROAD test cells for field performance.
Development of a Weigh-Pad-Based Portable Weigh-In- Motion System
Researchers developed a low-cost, portable and reusable weigh-in-motion system that can be used on rural local roads; evaluated the effects of pavement temperature and vehicle speed on its vehicle weight measurements; and compared these measurements to standard in-pavement systems. Results showed that it is possible to build and deploy a durable system with data quality similar to that of standard systems.
2011 Mainline Concrete Construction: Cells 5,6, and 63
In September 2011, MnDOT constructed two cells in the MnROAD Mainline in continuation of the study of
unbonded overlay (Cell 5) and to facilitate studies on a drainable base (Cell 6) with a longitudinal tined texture.
Additionally, roller compacted concrete shoulders were constructed in these cells, to replace the preexisting asphalt
shoulders. Finally, repairs were done to a thin concrete overlay of existing asphalt pavement installed in 2004 (Cell
63). This report discusses the construction procedure, instrumentation, and the initial monitoring from these test
2012-36 Structural Evaluation of Asphalt Pavements with Full-Depth Reclaimed Base
For bases mixed on-site with rubblized asphalt pavement and aggregate reclaimed from the pavement, MnDOT design standards require a granular equivalency (GE) equal to that of standard Class 5 aggregate. This study established GEs of stabilized and unstabilized FDR bases, finding stabilized bases provide a higher GE.
Researchers investigated how the material properties of recycled materials used in aggregate base layers of roads affect pavement performance by conducting laboratory tests on samples from eight states and monitoring newly constructed MnROAD test sections. Results showed that recycled concrete aggregate and recycled pavement material are suitable for unbound base course applications, demonstrating equal or better performance characteristics compared to natural aggregates in terms of stiffness, freeze-thaw and wet-dry durability, and toughness. MnDOT will update its materials specifications based on recommendations from this study.
Access to Destinations: Annual Accessibility for the Twin Cities Metropolitan Area
Researchers identified data sources, measures and methods for evaluating accessibility; built a set of tools that MnDOT can use to easily evaluate accessibility on a regular basis; and applied these tools to evaluating accessibility for the Twin Cities area in 2010. MnDOT will continue to evaluate the feasibility of incorporating accessibility into its performance measures and tracking it regularly for inclusion in its annual transportation performance report.
Investigators tested various length-based vehicle assessment methods with loops on Interstate 35 in Minnesota. Technologies for classifying vehicles by length can effectively supplement axle-based methods for assessing Average Daily Traffic and other traffic measures for use in planning and design activities. Such methods can also employ existing loop detectors and can be used in places where axle-based assessments are impractical.
Researchers created a guidebook to instruct MnDOT staff on proper messaging for permanent and portable CMS across the state. They also developed online presentation and training materials to help promote acceptance and understanding of the material over a broad spectrum of MnDOT employees and external stakeholders. The new manual combines a previously disparate set of CMS sources into a single resource, and will help improve the operation and effectiveness of MnDOT’s CMS system.
Implementation, Training, and Outreach for MnDOT Pavement Marking Tool - Phase II
The objective of this project was to fully implement the Pavement Marking Management Tool by incorporating retroreflectivity and striping data (MnDOT and contractors) and simplifying the process of data collection, storage, and analysis. As part of achieving full implementation, the researchers provided training to MnDOT central office staff and staff in each of the districts. Improved pavement marking management has the potential to reduce MnDOT's costs, improve pavement marking performance, and in return provide a more efficient and safe driving experience for the traveling public.
Full-Depth Precast Concrete Bridge Deck System: Phase II
Researchers evaluated the field performance of Precast Composite Slab Span System (PCSSS) bridges from three generations of design by conducting detailed deck crack mapping and core analysis as well as by analyzing strain data from a first-generation bridge instrumented during construction in 2005. Field inspections indicated that with some anomalies, the changes made between each PCSSS design generation generally improved performance. However, third-generation bridges still had significant issues with deck cracking. MnDOT is still working to address this problem and is currently limiting the use of PCSSS bridges.
Composite Pavements and Exposed Aggregate Texturing at MnROAD: Cells 70, 71, and 72 Construction Report and Early Performance Evaluation
This report summarizes the construction and early performance assessment of three composite (new, multi-layer, construction) test cells at the MnROAD: HMA over a recycled aggregate concrete; diamond grind concrete over recycled aggregate concrete; and exposed aggregate concrete over a low cost concrete. Strength, on board sound intensity, sound absorption, friction, texture and international roughness index were tested to better understand the performance of these, pavement types.
Investigation of Pedestrian/Bicyclist Risk in Minnesota Roundabout Crossings
Many pedestrians have expressed concerns about safety at newly installed roundabouts. Thousands of pedestrian and bicyclist crossings observed in this project, however, showed no evidence of reduced levels of safety, while wait times for pedestrians were significantly shorter than at signalized intersections.
A Research Plan and Report on Factors Affecting Culvert Pipe Service Life in Minnesota
Researchers evaluated factors affecting the service lives of culvert pipe materials. Then they developed guidance to help engineers maximize culvert service lives by choosing the materials best suited to the environments in which pipes will be placed and by using the most effective methods available for inspecting these pipes. In the study, researchers found that joint separation was a significant problem in concrete pipes and corrosion a problem in steel pipes.
Improving Technology to Alert Drivers to Work Zones
Researchers developed and tested a prototype Intelligent Drum Line system that can detect speeding drivers as they approach a work zone and deliver visual and audible warnings to attract their attention before they reach and endanger work zone flag operators. The IDL system successfully alerted drivers during prototype testing. Future development needs to ensure the system is crashworthy, can be produced cost-effectively and contains few components so it can be used in mobile operations.
Construction Manager/General Contractor Issue Identification
This study investigated aspects of a new method for contracting construction projects that should result in shortened construction times, lower costs and longer-lasting facilities: construction manager/general contractor (CM/GC) issue identification. MnDOT partnered with the construction industry to explore CM/GC as a Minnesota transportation contracting option and developed procedures and legislation to allow its use on a provisional basis.
Instrumentation, Monitoring, and Modeling of the I-35W Bridge
Researchers investigated the structural behavior of the I-35W St. Anthony Falls Bridge in response to traffic loads and temperature changes, using data from more than 500 sensors installed during construction. Results showed that the bridge behaved as expected during its first three years, and computer models accurately predicted its measured responses. Researchers also used this data to evaluate assumptions from the bridge’s Load Rating Manual, and ultimately it will help them to better understand the structural behavior of post-tensioned concrete box girder structures in general.
Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study - Phase II
Researchers developed fracture mechanics-based specifications for determining the low temperature properties of asphalt mixtures using the disk-shaped compact tension (DCT) test and semi-circular bend (SCB) test; continued Phase I testing of additional samples using recycled and other materials; investigated the physical hardening effects for modified asphalt binders; proposed and validated a method for obtaining mixture creep compliance from DCT and SCB results; and developed a new thermal cracking model, the ILLI-TC, a significant step forward in accurately quantifying the cracking mechanism in pavements.
This driving simulation study tested drivers' response to merge messages, speed limit signs and lane closure warnings presented on programmable overhead displays. Drivers responded appropriately to all of the messages, including an alternative format for merge messaging that was more effective than the standard words-only format.
Concrete Slurry, Wash, and Loss Water Mitigation
MnDOT has taken the lead in developing practices for adequately mitigating the impact of concrete slurry on the environment. This study identified best management practices for designers to use in controlling sediment during concrete operations.
Salt Brine Blending to Optimize Deicing and Anti-Icing Performance
This project developed a spreadsheet-based evaluation tool to compare the relative ice melt capacity and cost-effectiveness of granular and liquid deicers across a range of temperatures. A second phase of this research will validate and expand on lab results with field tests on actual pavements.
Potential Benefits of Mileage-Based User Fees to the Freight Industry and Industry Concerns
Researchers gathered information about the potential benefits of mileage-based user fees (MBUFs) to the commercial freight industry and identified industry concerns about costs, fee predictability, privacy and other factors. A literature review revealed a large body of recent research concluding that MBUFs would have a positive effect on transportation funding and lead to a more efficient use of transportation infrastructure. However, a focus group with trucking industry executives confirmed that the freight industry is adamantly opposed to MBUFs.
Subgrade Stabilization ME Properties Evaluation and Implementation
Researchers investigated methods and materials for stabilizing pavement subgrades to establish mechanistic empirical design parameters for the resilient modulus of stabilized roads. Results showed that there is a large variability in the degree to which stabilization improves the strength and stiffness of subgrade materials. Consequently, researchers could not identify one factor of improvement for a given combination of stabilization material and method. Instead they recommended that a procedure be followed on a project-by-project basis to identify an appropriate stiffness resistance factor during the course of project predesign and design. By collecting data on project-specific improvement factors, MnDOT will eventually be able to develop more general improvement factors. Doing so will reduce project costs by facilitating more precise pavement designs.
Material Testing Rates for Low-Volume Roads
Researchers reviewed MnDOT's existing Schedule of Materials Control (SMC) for its applicability to smaller projects by local agencies on low-volume roads. They created a new State Aid for Local Transportation program SMC for low-volume roads tailored specifically to the construction project risks encountered by local agencies, which reduces materials testing rates for low-volume projects without an unacceptable increase in risk. These guidelines incorporate feedback from MnDOT, local agency representatives and the construction industry, and include changes that remove some testing and inspection requirements and make others less stringent.
Validation of Prestressed Concrete I-Beam Deflection and Camber Estimates
Researchers developed a new method for predicting the release and erection cambers of Minnesota bridge girders by investigating the factors affecting their accuracy, including thermal effects, concrete strength and stiffness, solar radiation, relative humidity, concrete creep and shrinkage, length of cure and storage conditions. They developed prediction methods that on average improved release camber prediction accuracy from 74 percent to 99 percent, and erection camber prediction accuracy from 83 percent to 95 percent.
Lump Sum Estimating: Discovery and Simulation
Researchers evaluated the cost-effectiveness of changing from a unit pricing to a lump sum bidding process by comparing these methods with respect to total bid amount, time necessary for inspection, and the attitudes of contractors and MnDOT personnel. Results showed that the lump sum process is viable and produces similar bid results as the traditional process. Using lump sum bidding would require an improvement in the accuracy of construction plans as well as new guidance and training for inspectors whose responsibilities would shift from tracking quantities to performing quality control and assurance.
Highway Cost Allocation and Determination of Heavy Freight Truck Permit Fees
Researchers evaluated highway cost allocation methodologies, used this evaluation to customize the FHWA's HCA tool for Minnesota purposes, and performed HCA studies using both the FHWA tool and the Minnesota-centric tools. Researchers also evaluated the best tax structures for equitably collecting revenue and a method for optimizing the pricing of heavy vehicle special permits. Results showed that heavy vehicle users are not taxed proportionately to their impacts on Minnesota roads.
Assessment and Recommendations for the Operation of Standard Sumps as Best Management Practices for Stormwater Treatment (Vol. 2)
Researchers evaluated the effectiveness of standard sumps for removing and retaining sediments from stormwater runoff. While these sumps were effective for water moving at low rates from urban drainage basins smaller than four acres, they were unable to prevent captured sediments from washing out under high flow rates. The SAFL Baffle retrofit device developed in the second part of this study dramatically reduces this washout rate, making standard sumps very effective water treatment devices at one-fourth the prior cost.
Porous Asphalt Pavement Performance in Cold Regions
Full-depth porous asphalt test sections at MnROAD performed well in terms of draining and filtering water, providing excellent traction and noise absorption, and hastening snow and ice melt. While the test sections did exhibit rutting and surface raveling problems, their overall performance was acceptable and may well suit low-volume and reduced loading applications.
Mileage-Based User Fee Policy Study: Supporting Technical Information
The MBUF Policy Study was commissioned by the Minnesota Department of Transportation (MnDOT) to identify and evaluate issues related to potential future implementation of an MBUF system in Minnesota. Under a potential MBUF system, drivers would be charged based on the number of miles they drive, regardless of the type of energy source used to propel the vehicle, instead of being charged by the gallon for fuel consumed in operating a vehicle.
Use of StreetPave for Design of Concrete Pavements for Cities and Counties in Minnesota
This study compared RigidPave to StreetPave with a review of the input variables and design inputs used by surrounding departments of transportation. Existing thin (six inches or less) concrete pavements were also evaluated, which included both city and county pavements and test cells at MnROAD.
Development of Best Practices for Inspection of PT Bridges in Minnesota
Researchers conducted inspections of post-tensioned bridges built in Minnesota before 2003 and updated current bridge inspection procedures so that problems in these bridges can be detected and addressed. In general, the inspected bridges were in good overall condition. Invasive testing showed that one of the three bridges inspected showed no strand corrosion or grouting problems, one had major corrosion problems related to construction issues but appeared to have good grout, and one had significant problems with grouting and the beginning of corrosion. A follow-up implementation project will conduct a more detailed investigation of grouting in post-tensioned bridges.
Effects of Implements of Husbandry (Farm Equipment) on Pavement Performance
Agricultural equipment causes considerable damage to rural roads poorly suited for such massive loads. Researchers used instrumented test sections to measure the impacts of various farm implements and found that increasing axles on equipment and driving in the middle of the road can dramatically reduce pavement damage.
Rolling Resistance Measurements at the MnROAD Facility
Project researchers from the University of Gdansk, Poland, and Minnesota State University, Mankato, obtained and analyzed rolling resistance data for Cells 7, 8, and 9 of the MnROAD mainline. They also conducted a comparison of the rolling resistance to surface texture, friction, and noise.
Vehicle Speed Impacts of Occasional Hazard (Playground) Warning Signs
This research project evaluated whether installing playground warning signs near three parks in Bloomington affected vehicle speeds. Researchers found that the signs had very little impact, but that drivers did slow down when playgrounds were busy and when there were many cars parked along the street.
Using Twin Cities Destinations and their Accessibility as a Multimodal Planning tool: Task 5 Report
Researchers evaluated how accessibility in the Twin Cities region would be affected by various changes in land use (including population and employment scenarios) and the transportation network (due to proposed highway infrastructure improvements and public transit investments). Results showed that centralized growth in population and employment produced the highest accessibility, followed by centralized population and decentralized employment. However, because of increasingly decentralized population and employment along with the infeasibility of a free-flowing highway network, investments in congestion pricing and high occupancy toll lanes may be the best strategies for maximizing accessibility.
Development of Freeway Operational Strategies with IRIS-in-Loop Simulation
Developing efficient and robust traffic control strategies that can directly be implemented in the existing operational environment is of critical importance in improving the effectiveness of freeway management. Currently the freeway network in the Twin Cites is being managed with the Intelligent Road Information System (IRIS), a computerized operating system developed by MnDOT to control the field devices such as ramp meters, variable message signs and loop detectors. This research develops a comprehensive support and development tool for IRIS by integrating it with a microscopic traffic simulator. The resulting IRIS-In-Loop simulation system (ILSS) can be used to emulate and refine various types of freeway operational strategies prior to field implementation. As a first application of ILSS, an alternative ramp metering strategy will be developed in this research and evaluated with ILSS. Further, a computerized process will be developed to estimate a set of traffic condition measures for given freeway corridors with selected time periods. The quantified measures can be used to support different levels of decision making process at MnDOT in planning and operating the freeway network.
Evaluating the Cost and Benefits of Living Snow Fences
Researchers developed a calculator for estimating Living Snow Fences program payments to landowners by identifying costs, benefits and obstacles to implementing the program, including landowner costs and constraints, agency constraints and potential agency benefits from avoided carbon emissions and avoided snow removal and safety costs. Recommendations include offering shorter and more flexible LSF contracts, increasing compensation at key locations, adjusting payments for inflation, tying payments to corn and land prices, increasing payments in the first three years to offset maintenance, reducing risk and landowner liability, compensating for replanting and increasing awareness. By contracting 40 percent of sites with snow problems to LSF, MnDOT could save $1.3 million per year.
Using Computer Modeling to Improve the Design of Unbonded Concrete Overlays
Researchers evaluated existing design procedures for unbonded concrete overlays, including MnDOT guidelines, by analyzing UBCO crack propagation using a computer model that relates the load capacity of a pavement to its dimensions and material properties, including fracture energy. Results suggest that this model shows promise for improving UBCO design by determining the load capacity of a new single-layer portland cement concrete pavement designed using current procedures, and then determining thickness and material properties for a UBCO that will yield the same load capacity.
Best Value Granular Material for Road Foundations
Researchers evaluated how mechanistic-empirical design procedures can be used to make effective use of local Minnesota aggregates in the unbound pavement layers of flexible pavements by determining how aggregate properties such as angularity and surface texture affect aggregate quality as measured by resilient modulus and shear strength. Results showed that aggregate angularity and surface texture were more important to determining the resilient modulus of aggregates than gradation alone, and that use of locally available materials can be cost-effective for low-volume roads with 20-year design traffic level and no more than 1.5 million equivalent single-axle loads.
Estimating the Traffic Impact on County Roads from Wind Turbine Construction
Researchers developed an Excel-based calculator to estimate the impact of wind farm construction traffic on county roads. Traffic for a single construction project can easily consume half of a county road’s expected 20-year life span in one season. The tool helps to fix costs for developers, keep construction on schedule and help counties recoup costs.
Putting Research into Practice: ADA Transition Plan for Public Rights of Way
Investigators developed a guide for local agencies to create transition plans to bring their public rights of way into compliance with the Americans with Disabilities Act, as required by law. The guide includes a step-by-step process, model transition plans and supporting documents.
Pooling Our Research: Urban Mobility Study
The study focuses on developing tools to monitor and evaluate urban congestion by identifying and evaluating the latest mobility data sources, developing and communicating comprehensive performance measures for congestion improvements and helping member agencies apply the study's research products to their congestion planning.This Urban Mobility Study is nationally recognized as the leading resource for traffic congestion research.
Pooling Our Research: Using Recycled Shingles in Asphalt Pavements
Researchers conducted a literature review of nationwide applications of manufactured and tear-off shingles, focusing on specifications, case studies, demonstration projects and environmental safety. Member states involved in this study have developed quality control and assurance procedures for sourcing and processing RAS, and have conducted their own demonstration projects for both post-manufactured and post-consumer RAS to develop mix design criteria and construction specifications. These specifications generally allow up to 5 percent post-manufactured RAS in HMA when used with RAP, and also set the required percentage of virgin binder and place limits on the percentage of allowable deleterious content.
As part of this pooled fund study, MnDOT evaluated MnROAD test sections using post-manufactured and post-consumer RAS. Researchers conducted laboratory and field tests to evaluate the effects of binder grade and content as well as RAP or RAS source and content on the performance of HMA mixtures, especially on low-temperature cracking and stripping. Results published in the 2010 report "Incorporation of Recycled Asphalt Shingles in Hot-Mixed Asphalt Pavement Mixtures" confirmed MnDOT specifications requiring at least 70 percent new asphalt binder and led to provisional specifications allowing for the use of up to 5 percent post-manufactured and post-consumer RAS in both surface and base mixes for plant-produced asphalt mixtures under Specification 2360.
Pooling Our Research: Improving Winter Maintenance with New Technologies
As state DOTs aggressively pursue new technologies and practices for improving winter highway operations, Clear Roads supports their evaluation in both the laboratory and the field to develop industry standards, performance measures and cost-benefit analyses, practical field guides and training curricula. The scope of the effort is currently expanding to focus on state agency needs, technology transfer and implementation, including support for staff in the field.
Pooling Our Research: The Transportation Engineering and Road Research Alliance
Since 2004, the Transportation Engineering and Road Research Alliance (TERRA) has focused on fostering pavement research innovation and implementation, and broadening the unique capabilities of MnROAD, Minnesota’s state-of-the-art outdoor pavement research facility. TERRA supports a comprehensive program of pavement research, including issues related to cold climates, and provides a network for collaboration and information sharing between industry, academia and public agencies. TERRA also focuses on communicating findings and hosts seminars, workshops and an annual pavement conference.