2013 Reports and Technical Summaries
Implications of Modifying State Aid Standards: Urban Construction or Reconstruction to Accommodate Various Roadway Users
This project reviewed 11 urban sites where roadways underwent Complete Streets reconstruction projects—the introduction of features such as narrowed lanes, parking lanes, pedestrian terraces or curb extensions designed to make roads more usable by nonmotorized travelers. Crash data from these sites suggested no significant negative safety impacts as a result of the Complete Streets implementations, and anecdotal evidence suggested no negative impact on operations.
Complete Streets from Policy to Project guidebook
Many communities in Minnesota and nationwide are working to incorporate Complete Streets concepts into their transportation construction projects. This project examined 11 successful Complete Streets projects from large and small communities around the country to identify best practices that other jurisdictions can adapt to their own unique needs.
Implementation of Pavement Evaluation Tools
Investigators updated MnDOT’s falling weight deflectometer analysis software, GopherCalc, to incorporate ground penetrating radar, the latest analysis methods and a user-friendly graphical user interface. The software updated in this project will allow county and state engineers to more easily evaluate pavements using FWD and GPR data.
Performance-Based Measurement of Optimum Moisture for Soil Compaction
Part of the challenge achieving maximum field density in subgrade materials is transferring the optimal compaction and moisture content data from laboratory testing to the field. This research investigated the proficiency of four different instruments at accurately predicting moisture contents of three subgrade soils (loam, silt, silty/clay) commonly used in Minnesota roadway construction projects. The four instruments were; DOT600 (moisture content), WP4C dewpoint potentiometer (matric suction), the Button Heat Pulse Sensor (BHPS) (temperature rise vs. moisture content), and an exudation pressure test device.
Designing a Portable, Batteryless Weigh-in-Motion System for Local Roads
Researchers sought to refine a low-cost weigh-in-motion sensor for use on local asphalt roads. While they did develop a system that could be embedded in and grouted to asphalt pavement, the sensor is too large, and concerns that it could be dislodged and damage vehicles prevented its implementation.
Testing a Friction Measurement System in Polk County
A friction measurement system tested on two snowplows in Polk County found that the county’s current winter maintenance practices are adequate to keep roads in passable condition during snowstorms. Both the original system and a reinforced version, however, failed after only a few days of use.
Toolbox of Countermeasures for Rural Two-Lane Curves
Final Report (PDF, 3.3 MB, 83 pages)
The Federal Highway Administration (FHWA) estimates that 58 percent of roadway fatalities are lane departures, while 40 percent of fatalities are single-vehicle run-off-road (SVROR) crashes. Addressing lane-departure crashes is therefore a priority for national, state, and local roadway agencies. Horizontal curves are of particular interest because they have been correlated with increased crash occurrence. This toolbox was developed to assist agencies address crashes at rural curves. The main objective of this toolbox is to summarize the effectiveness of various known curve countermeasures. The toolbox is geared toward rural two-lane curves. The research team identified countermeasures based on its own research, through a survey of the literature, and through discussions with other professionals.
Protocols and Technologies for Monitoring Non-Motorized Traffic
Measuring bicycle and pedestrian traffic is in its infancy, and a current lack of data makes it difficult to know the effectiveness of investments and active transportation-related safety and health initiatives. This project developed guidelines and protocols for manual field counts, held pilot field counts and analyzed automated count technologies to determine how they can be used together to give a more complete picture of bicycle and pedestrian traffic.
Developing a Handbook for Trail Crossing Safety Treatments
Researchers developed a handbook and training presentation that synthesize best practices in Minnesota and nationwide for trail crossing safety treatments to provide engineers and other transportation professionals with a unified source of guidance. As part of the handbook, researchers developed a unique, decision-tree-based treatment selection methodology, allowing users to rapidly search for and select appropriate treatments based on different conditions at a particular trail crossing.
Best Practices for Pedestrian/Bicycle Safety
This project produced a guide to 19 strategies for improving bicycle and pedestrian safety commonly requested by bicycle and pedestrian advocates. The guide synthesizes current research to help city and county engineers assess the true benefits and costs of each strategy to build the safest possible transportation network for all users.
Use of Recycled Brick in Aggregates
Researchers evaluated recycled brick for its suitability as an aggregate material in base and surface courses. Most types of brick performed well in tests of absorption, abrasion resistance and weathering resistance. However, due to concerns about severe negative consequences if field performance does not match laboratory tests, MnDOT standards will permit recycled brick in aggregate only in proportions up to 1 percent by mass.
Updating MnDOT Guidance for Using Shredded Tires in Roadway Construction
This project synthesized published research about the use of tire-derived products in roadway construction, with a focus on the use of shredded tires in lightweight fill, retaining wall backfill, insulation layers, drainage layers and capillary moisture breaks. The information collected will be used in a review of MnDOT’s standards, which were based mainly on research conducted in the 1980s and 1990s.
Extending the Twin Cities Cyclopath Tool to Enable Multimodal Routing
Researchers incorporated multimodal routing into the Cyclopath bicycle route-finding tool to allow users to find routes that combine biking and transit for journeys where biking alone is impractical. Increasing the percentage of trips made by methods other than cars is a MnDOT priority, and providing route information can help to make alternative transportation options more viable.
PCC Surface Characteristics - Rehabilitation MnROAD Study
Researchers evaluated the noise levels, ride quality, friction and texture of various diamond grind textures on test cells at the MnROAD pavement research facility. They found that while the innovative grind had the least noise immediately after grinding, for long-term performance the ultimate grind had the least noise and best friction for ribbed tires, while the innovative grind had the best friction and texture for smooth tires.
Improving Traffic Signal Operations for Integrated Corridor Management
This project continued research into using the SMART-SIGNAL real-time traffic monitoring system to mitigate traffic congestion. Investigators developed and simulated signal timing strategies to reduce oversaturation at signalized intersections and a strategy for diverting traffic between freeways and parallel arterials during peak hours or after traffic incidents.
Pavement Texture Evaluation and Relationships to Rolling Resistance at MnROAD
Researchers developed a detailed three-dimensional representation of pavement textures at MnROAD using the RoboTex line-laser profiler, and related this and other pavement surface characteristic data to rolling resistance. Results showed that there are many possible combinations of surface characteristic variables that can predict rolling resistance in pavements, with skewness particularly important for concrete and macrotexture level for asphalt.
Optimizing the Use of Recycled Asphalt in Minnesota Roads
Researchers evaluated the performance of high recycled asphalt pavement mixtures—those with more than 30 percent RAP—by evaluating their field performance; the blending of RAP with virgin aggregate in the plant and laboratory; and low-temperature strength, creep and fracture energy. Results showed an improvement in using PG-34 binder rather than PG-28 binder with RAP, good activation in plant mixing and less crack resistance with higher amounts of RAP.
Mobility Performance Measures for Arterial Streets
Researchers used commercially available GPS travel speed data for arterial streets in the Twin Cities Metropolitan Area to develop performance measures as well as performance targets based on context and land use. MnDOT will ultimately be able to use this data as it works to address congestion on arterial streets. Researchers also identified the most congested arterial streets in the metro area.
Mitigating Highway Construction Impacts Through the Use of Transit
Researchers examined how transit could be used to mitigate the impact of a major and highly disruptive road construction project in Duluth, Minnesota, as well as the factors that determine whether people who switch to transit during the construction project continue using it when the project is completed. Research indicated that once a disruptive event induced drivers to try transit, they tended to stay with it as long as that service remained adequate to their needs.
Wakota Bridge Thermal Monitoring Program Part II: Data Analysis and Model Comparison
Final Report (PDF, 6.32 MB, 167 pages)
In this work, a common refined design method is evaluated with respect to a recently constructed bridge. Two finite element models of the Wakota Bridge in South St. Paul, Minnesota were produced using a design level program (SAP2000). These models were analyzed and their results compared to the data collected from the bridge. The second half of this study concerned the comparison of the collected field data with the values produced by evaluating the design-level finite element models previously created in Phase I of the project, and calibrating these models to provide an accurate prediction of the future behavior of the bridge.
Wakota Bridge Thermal Monitoring Program Part 1: Analysis and Monitoring Plan
In this work, a common refined design method is evaluated with respect to a recently constructed bridge. Two finite element models of the Wakota Bridge in South St. Paul, Minnesota, were produced, one using a design level program (SAP2000) and the other using a research level program (ABAQUS). These models were verified with respect to each other using linearly elastic materials and were found to behave similarly. After this verification, an arbitrary temperature load was applied to each model and the refined design method was evaluated for accuracy of reduced section properties with respect to the more descriptive progressive cracking solution simulated by ABAQUS.
Using Concrete Maturity Testing to Optimize Road Opening Timing
Researchers developed strength-maturity relationships in concrete that allow contractors, field personnel and materials engineers to reduce the sampling and testing necessary to estimate the strength of concrete pavement mixes that have high supplementary cementitious materials content and low water-cement ratios. Overall results showed that MnDOT can use the maturity method to accurately predict the strength of portland cement concrete. Researchers also developed a database of concrete mixes and their associated maturity curves, created a draft construction specification and produced a draft laboratory manual detailing the use of maturity curves for portland cement concrete pavement construction projects.
Synthesis of Bridge Approach Panels Best Practices
Joints between the approach panel and the pavement on integral and semi-integral abutment bridges in Minnesota often fail prematurely due to compression and expansion from the state's wide temperature swings. This project surveyed nearby state and provincial transportation departments to learn their practices for these types of joints. Strip seals, neoprene compression seals from D.S. Brown and Sealtite polyurethane foam are recommended for further consideration in Minnesota.
Stripping of Hot-Mix Asphalt Pavements under Chip Seals
Researchers conducted a survey, tested field samples in the laboratory and reviewed construction methods to determine why hot-mix asphalt pavement stripping occurs in some Minnesota streets after placement of asphalt chip seal, and to determine methods for preventing and remedying stripping. Results suggest that stripping is caused by variability in density due to inadequate compaction, and it can be prevented by using a nuclear density gauge to qualify candidates for chip seals and by taking random core samples from pavements during rolling.
Understanding the Economic Effects of Flexibility through Three Employer Case Studies
Broader business acceptance of flexible workplace policies would reduce congestion and make more efficient use of roadways. This study attempted to validate these policies from a business perspective through three case studies of flexible workplace organizations. Both employees and managers described the policies as resulting in reduced turnover and improved productivity with increased employee satisfaction. Although economic benefits can be inferred from these factors, they were not directly observed.
Research Implementation of the SMART-SIGNAL system on Trunk Highway (TH) 13
Investigators upgraded the SMART-SIGNAL (Systematic Monitoring of Arterial Road Traffic and Signals) system by making field hardware more compact and easier to install. They also developed a Web-based interface for traffic control center software, allowing the generation of real-time arterial performance measures and historical statistical reports. Investigators implemented the refined system at 13 intersections along Trunk Highway 13 in Burnsville, Minnesota.
Quality of Life: Assessment for Transportation Performance Measures
This project sought Minnesota citizen input through focus groups and mail surveys to define quality of life, identify the role transportation-related factors play in it and investigate how MnDOT is performing on those factors. Accessibility, safety, maintenance and mobility were rated the most important factors. Overall, Minnesota residents were fairly well-satisfied with MnDOT services, with 84 percent rating performance at least 5 on a 7-point scale.
46th Street Pilot Street Lighting Project
Investigators installed 55 energy-efficient streetlights along a section of 46th Street in south Minneapolis. This project evaluated the cost-effectiveness and lighting quality of both LED and induction light technologies, and compared products from several manufacturers and vendors. LED streetlights were found to provide adequate lighting quality. This technology may soon be cost-effective for general use.
Case Studies of Transportation Investment to Identify the Impacts on the Local and State Economy
Four case studies of transportation projects were evaluated to determine their impact on local economic activity. Researchers found no evidence of statistically significant impacts on earnings and employment, although a broader evaluation of user benefits may be appropriate in determining their value. These case studies support the suggestion that highway networks in the United States are largely mature, and new investment is subject to diminishing economic returns.
Design and Construction Guidelines for Thermally Insulated Concrete Pavements
Researchers performed life-cycle cost analysis comparisons and developed design and construction guidelines for thermally insulated concrete pavements (TICPs). They also examined the applicability of the Mechanistic-Empirical Pavement Design Guide (MEPDG) and California models to TICPs. Results uncovered significant issues with the MEPDG’s climate model, leading to recommended corrections. Researchers developed their own models and a software companion to the MEPDG that incorporates the models. The final report includes construction guidelines for composite pavements and a life-cycle cost analysis comparing the costs of TICPs with jointed plain concrete pavements.
Instrumentation of Navistar Truck for Data Collection
Final Report (PDF, 2.2 MB, 34 pages)
The overarching goal of this project was to instrument the new MnDOT Navistar truck used at MnROAD. A rugged data acquisition, data recording and wireless transmission system was established for collection of various sensor signals from the truck. The truck was instrumented with a suite of 20 accelerometers, with these accelerometers being located both on the five axles of the truck and on the tractor and trailer bodies. In addition, the truck was instrumented with a differential GPS system and an inertial measurement unit in the tractor cab. A cRIO-based data acquisition system, a rugged laptop and Labview software together serve as a flexible platform for data acquisition. The above instrumentation of the truck will enable data collection on truck vibrations, enable analysis of correlations between truck vibrations and variations in signals of weigh-in-motion sensors, and enable recording of truck movements and pavement loads at MnROAD.