2008 Technical Summaries
Self-Compacting Concrete for Prestressed Bridge Girders
Self-compacting concrete offers significant cost benefits in precast girder construction, but performance testing and mix design standards were needed to enable use of SCC in Minnesota. Researchers evaluated wet-state performance of a range of mixes, and cast and instrumented four full-scale girders for laboratory performance testing.
They also cast numerous cylinders to monitor physical characteristics and create performance models. They found SCC to be a suitable construction option.
“Mn/DOT is more confident now that beams produced with SCC have been shown capable of providing satisfactory, long-term performance in Minnesota bridges.”
– Erik Wolhowe, Bridge Consultant Contracts Coordinator, Mn/DOT Metro District
Investigating the Effects on Wildlife of Reed Canarygrass Infestation of Minnesota Wetlands
Habitats that contain reed canarygrass have been found to have lower diversity of traditional native plants, causing researchers to posit that the lower diversity of vegetation resulting from the invasion of reed canarygrass will have a corresponding negative effect on wildlife. While results of this study did not indicate a clear negative impact on wildlife from the invasion of reed canarygrass, researchers did note effects were more evident at lower trophic levels, negatively influencing the plant and invertebrate communities.
“The fact that we were unable to find four native study sites completely free of reed canarygrass highlights the significance of this problem.”
– Kenneth Graeve, Botanist/Plant Ecologist, Mn/DOT Office of Environmental Services
Improved Methodologies for the Inoculation of Prairie Legumes in Roadside/Revegetation Settings
Researchers have identified that legumes and the level of nitrogen they can contribute are integral to prairie development. Mn/DOT includes a number of indigenous legumes in its roadside vegetation and wetland restoration plant mixes. Better inoculant delivery systems are needed to ensure that the strains being used are able to persist and function under revegetation conditions. This study recommends the use of granular soil-applied peat inoculant.
“The results of this study show strong benefits with the methods identified in the research. We can apply these methods in field trials as a first step in modifying our seeding specifications.”
– Kenneth Graeve, Botanist/Plant Ecologist, Mn/DOT Office of Environmental Services
Corrosion Performance of Epoxy-Coated Reinforcement Bars
High salt levels on the roadways from deicing agents can lead to serious corrosion of uncoated steel reinforcement in bridge decks. Since the 1970s, reinforcing bars have been coated with epoxy to protect them from corrosion. In this study, researchers revisit four bridges that were examined 10 years ago to evaluate the continuing performance and level of corrosion of the epoxy-coated reinforcing bars.
“We were glad to see that the coating was performing effectively and that our specifications won’t require any significant changes.”
– Paul Rowekamp, Mn/DOT Bridge Standards & Research Engineer
Safety Effects of Centerline Rumble Strips in Minnesota
Centerline rumble strips are a safety treatment that is gaining momentum nationally and internationally as an effective, low-cost treatment that can reduce centerline-crossing crashes. This report examines the relationship between centerline rumble strips and traffic safety on rural Minnesota roadways and makes recommendations for centerline rumble strips best practices.
“Because Marc Briese conducted this study as the Capstone project for his infrastructure systems engineering degree, there was no cost to Mn/DOT in acquiring this valuable research.”
– Sue Lodahl, Director, Mn/DOT Research Services Section
Intelligent Transportation Systems
Improving Carsharing and Transit Service with ITS
Intelligent Transportation Systems apply technologies to solve surface transportation problems. Two ITS applications—carsharing and Advanced Transportation Information Services—could bring significant benefits to Minnesota residents by providing increased mobility and access to transit services. Researchers surveyed members of HOURCAR, a nonprofit Twin Cities carsharing organization, to gain a better understanding of CSO users in the Twin Cities. Users of Metro Transit’s online trip planner were surveyed to assess how their perceptions of trust and confidence in the transit agency were affected by their use of the online trip planning service.
“Carsharing organizations in the Twin Cities can use the results of this study to more thoroughly understand their market and adjust their services to make their programs more viable.”
– Ken Buckeye, Program Manager, Mn/DOT Office of Policy Analysis, Research & Innovation
Environmental Effects of Deicing Salt on Water Quality in the Twin Cities Metropolitan Area
Using salt to deice roadways in winter plays an important role in providing for the driving safety of Minnesotans. The objective of this research was to learn more about what happens to sodium chloride, the primary chemical used for deicing purposes, after the road salt has completed its job of providing safer winter roadways.
“We can use the information from this study to better manage our use of road salt, minimizing impacts while still maintaining safe roadways.”
– Wayne Sandberg, Deputy Director of Public Works, Washington County
Validating Mn/DOT's Precast Composite Slab Span System
Investigators studied the effectiveness of a new design for short-span bridges, monitoring and analyzing bridges in the field and in the laboratory, paying special attention to the development of cracking in the deck above the joints of the bridge.
“Mn/DOT uses lots of slab-span bridges, but the biggest potential use of these bridges is on county and State Aid highways, not trunk highways. There are hundreds of bridges on the State Aid highway side that could be replaced with this design.”
– Keith Molnau, Design Unit #2 Leader, Mn/DOT Office of Bridges and Structures
Production and Wind Dispersal of Canada Thistle Seeds
Researchers sought to understand the role that wind dispersal and seed production play in the spread of Canada thistle infestations. They found that wind dispersal is not as significant a factor in Canada thistle seed movement as was commonly thought.
“Adapting management practices to the realities of Canada thistle dispersal could make controlling this weed considerably less costly and more environmentally friendly.”
– Tina Markeson, Mn/DOT Senior Natural Resource Forestry Specialist
Pavement Marking Software
Developing and Implementing Enhanced Pavement Marking Mangement Tools: Phase I - Mapping Tool
Mn/DOT needed an application to support easy online viewing and querying pavement marking data to enable consistent, objective and cost-effective decisions regarding pavement marking needs. Phase I of this multiphase project engaged the Center for Transportation Research and Education at Iowa State University to create a mapping tool to graphically display pavement retroreflectivity data.
“The Pavement Marking Management Tool and its initiative is 100 percent in line with Mn/DOT’s Strategic Plan: ‘Mn/DOT will continuously improve service and efficiency in order to give citizens the best value for their tax dollars by encouraging innovation…through creative, cost-saving solutions.’”
– Sue Groth, Director, Minnesota Office of Traffic and Safety
Generational Perspective on Teen and Older Drivers on Traffic Safety in Rural and Urban Communities
Researchers examined the differences between the experiences and perceptions of high-risk rural and urban drivers—teens and seniors—in connection with driving purpose, crash risk, risk factors associated with crash reduction, and safety interventions. These findings will contribute to the development of effective safety intervention programs targeted to high-risk drivers.
“This study indicates a difference in perception between age cohorts with regard to crash risk: Distractions were problematic for teens, while senior drivers cited the deterioration of perceptual, cognitive and psycho- motor processes.”
– Gordy Pehrson, Traffic Safety/Youth, Alcohol Coordinator, Minnesota Office of Traffic Safety
Runoff and Sediment Software
Design Tool for Controlling Runoff and Sediment from Highway Construction
Storm water runoff from construction sites can degrade the quality of waters in streams and lakes. To control runoff and create best management practices, developers enhanced a software tool that simulates the impact of highly variable weather conditions on runoff and erosion. The enhanced version factors in both on- and off-site construction variables, and improves modeling capabilities. Additional work is planned to further improve the user interface.
“If not controlled, sediment can impede water flow and reduce water quality. The enhanced WATER simulation tool will provide a more scientific way of defining and managing the erosion risks of construction projects so we can minimize the environmental impact.”
– Brett Troyer, Principal Engineer, Mn/DOT Environmental Services
The Impact of Bicycling Facilities on Bicycle Commuting Levels
Researchers investigated whether the presence of new bicycle facilities could be correlated with an increase in bicycle commuting rates in various U.S. cities. By mapping facilities constructed in the 1990s and analyzing changes in census data, researchers found no evidence that facilities have a stand-alone effect on bicycle commuting rates. Interviews with city bicycle coordinators revealed the influence of factors including the location of facilities, overall network connectivity and promotion efforts.
“The value of the first Twin Cities study was developing the methodology. The value of this study was learning if the findings hold true in other locations and developing additional sociological methodologies to explain why.”
– Darryl Anderson, State Bicycle and Pedestrian Coordinator, Mn/DOT Office of Transit
Light-Emitting Diode Lighting
LED Emergency Lighting for Snowplows and Other Maintenance VehiclesResearchers evaluated the safety and effectiveness of equipping Mn/DOT snowplows with LED-based strobe lights, which are more efficient and cost-effective than standard HID lights. Results showed that while LED lights are as conspicuous as HID for standard driving conditions and viewing angles, they are not as visible when approached from a variety of other viewing angles. Further research is needed to determine whether these angles are relevant to safety.
“LED-based strobes should be more cost-effective on snowplows than standard strobes because they last longer and use less current.”
– Farideh Amiri, Maintenance Operations Research Engineer, Mn/DOT Office of Maintenance
Design Procedure for Bituminous-Stabilized Road Surfaces for Low-Volume Roads
Researchers found that bituminous stabilization of low-volume gravel roads is more cost-effective than maintaining gravel surfaces or upgrading to hot-mix asphalt, creates fewer dust problems, and increases driver safety. Investigators also developed procedures and software to make design choices easier and more reliable than decisions based on empirical estimates.
“Regrading and replacing aggregate on gravel roads are expensive measures. This study confirmed the decisions we have been making about bituminous stabilization.”
– Alan Forsberg, Public Works Director, Blue Earth County
Changeable Message Signs
The Effectiveness and Safety of Traffic and Non-Traffic Related Messages Presented on Changeable Message Signs: Phase II
Researchers evaluated how reducing the complexity and ambiguity of CMS messages would affect driver behavior and traffic flow, and learned that clarifying message content could lead to significant improvements in CMS safety and effectiveness.
“This study provided valuable information to validate our operating procedures, the way we structured the new messages and the fact that the content of the CMS messages is more important than their location.”
– Todd Kramascz, Operations Supervisor, Traffic Operations Section, Mn/DOT Regional Transportation Management Center
Traffic Volume Thresholds for Requiring Right Turn Lanes and Treatments on Two-Lane Roads
Mn/DOT’s right turn lane volume warrants were generally based on qualitative assessment rather than quantitative analysis, resulting in inconsistent application of right turn lanes and an inability to ensure cost-effective intersection design. This research project developed procedures for establishing and applying volume-based warrants that strike a balance between the cost to build a right turn lane or treatment and the money it will save in safety and operational benefits.
“The volume thresholds developed in this project provide Mn/DOT with legally defensible criteria for requiring private developers to establish right turn lanes.”
– Brian Gage, Access Management Engineer, Mn/DOT Office of Investment Management
Determining the Impacts of Roundabouts on Roadway Networks
Roundabouts are gaining in popularity as a method for controlling traffic flow at particular intersections or portions of roadway corridors. They may, however, negatively affect overall system performance. Mn/DOT developed a toolbox to help cities, counties and other agencies accurately assess the impact of roundabouts on different kinds of highway systems and corridors.
“Transportation providers can avoid unintended problems when roundabouts are considered first from a ‘big picture’ perspective rather than as isolated, individual intersections.”
– Paul Stine, Mn/DOT State Aid Engineer for Local Transportation
Effects of Seasonal Changes on Ride Quality at MnROAD
Investigators found that frost heave, a common problem in winter weather, occurs less frequently and with less severity in thick pavements, in well-draining pavements and in those built over sand subgrades rather than clay subgrades.
“This study confirmed our current practices in responding to frost heave, but didn’t provide enough input to change our design specifications. Improving data collection and ride analysis methods may offer more insight.”
– Benjamin Worel, MnROAD Operations Engineer, Mn/DOT Office of Materials
Putting Research into Practice: Intelligent Compaction Implementation—Research Assessment
This project provided a qualitative assessment of Mn/DOT’s intelligent compaction specifications and procedures, with recommendations for improving IC practices, including the use of lightweight deflectometers for quality assurance, improving equipment calibration techniques and streamlining IC data processing.
“Mn/DOT is on the forefront of intelligent compaction research, and this implementation will be an important resource for other state DOTs that are also exploring more efficient compaction technologies.”
– Rebecca Embacher, Mn/DOT Assistant Grading and Base Engineer
Trash Harvesting Machine
Designing a Machine for Picking Up Litter Along Minnesota Highways
Collecting trash by hand along highway shoulders and medians in the Twin Cities metropolitan area costs about $2 million per year, is time-consuming and presents serious safety hazards for Mn/DOT workers. Investigators designed a prototype “trash harvester” for picking up litter in grassy areas. While this prototype did not perform to Mn/DOT expectations and will not be commercialized at this time, it provides a starting point for further research, design and testing.
“With additional modifications, the trash harvester will be a safer and more cost-effective way to keep Minnesota highways clean.”
– Jonathan Chaplin, Associate Professor, University of Minnesota Department of Bioproducts and Biosystems Engineering
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Putting Research into Practice: Best Practices Handbook for Roadside Vegetation Management 2008
This project updated the 2000 handbook in light of recent Mn/DOT studies related to roadside management. The updated handbook includes a new chapter on managing roadside vegetation for wildlife and vehicle safety.
Technical Summary: 200820TS (PDF)
Full Report: 2008-20 "Best Practices Handbook for Roadside Vegetation Management 2008" (PDF)
“The 2000 handbook was a great resource for roadside managers, but we needed a synthesis of new research on the relationship between vegetation, wildlife and driver safety—which the updated handbook provides.”
– Paul Walvatne, Mn/DOT Roadside Vegetation Management Unit Supervisor
Cable Median Barriers
Predicting the Cost-Effectiveness of highway Median Barriers
Median barriers are an effective but costly countermeasure for cross median crashes on divided highways. Researchers developed tools Mn/DOT can use to identify highway sections at high risk for these crashes and predict the costs and benefits of installing cable median barrier on a given highway section.
– David Engstrom, State Traffic Safety Engineer, Mn/DOT Office of Traffic, Safety and Technology
Turn Lane Lengths for Various Speed Roads and Evaluation of Determining Criteria
Researchers developed user-friendly equations to enable Mn/DOT road designers to accurately calculate the optimal length for turn lane storage bays. This study also identified parameters, including speed and traffic volume, that should be considered when designing a turn lane, and quantified their influence on turn lane operation.
“Data from this study will improve our ability to determine optimal turn lane length under differing types of conditions.”
– Glen Ellis, Mn/DOT Metro District Design Engineer
Geographic Information Systems
Improving the Predictive Accuracy of Mn/Model: Modeling Historic and Prehistoric Surface Water Features
Researchers developed automated methods for modeling historical and prehistoric surface water features from GIS data already available to enhance the predictive accuracy of Mn/Model, a GIS-based model that predicts the potential of archaeological sites within the state of Minnesota. The research resulted in the development of the ArcGIS Toolbox Historic Water Features Tools, which create a new GIS layer of historic and prehistoric hydrologic features.
“The new Historic Water Features Tools make Mn/Model more accurate by identifying locations of water bodies, such as drained lakes, that are not present in modern hydrographic data.”
– Elizabeth Hobbs, State Program Administrator Coordinator/Geographer, Cultural Resources Unit, Mn/DOT Office of Environmental Services
Freight Performance Measures
Assessing Mn/DOT’s Freight Performance Measures
Researchers assessed Mn/DOT’s current freight performance measures by identifying more general industry measures, finding available public and private sector freight information sources required for the application of these measures, assessing the cost of using these information sources, and examining the relevance of source data to Mn/DOT. These measures will aid long-range planning efforts for improving Mn/DOT’s freight transportation system, including the update of the Statewide Transportation Plan.
“By comparing external data to existing Mn/DOT data, we gained a much better understanding of our performance measures. This data is critical to compiling the state’s transportation plan.”
– Robert Gale, Planner Principal Transportation, Mn/DOT Office of Freight and Commercial Vehicle Operations
Ground Penetrating Radar
Pavement Evaluation Using Ground Penetrating Radar
This research developed an improved method for using ground penetrating radar data that allows users to determine pavement thickness and the presence of subsurface moisture while driving a GPR van at speeds up to 50 mph, even without having design and construction records about the pavement.
“This technology is great. If you want to redesign a distressed pavement, you have to know the pavement’s thickness. This gives us a continuous profile of the pavement rather than information from specific cores at a limited number of points.”
– Shongtao Dai, Mn/DOT Research Operations Engineer
Improving Capacity Planning for Demand-Responsive Paratransit Services
Researchers analyzed archived paratransit data to create models and algorithms that can be used to help implement two approaches for improving efficiency: reoptimizing routes and selectively using nondedicated service providers such as taxis. Both measures could provide a cost savings for local transit agencies and service providers.
“Beyond its immediate utility for Metro Mobility, this study also has the potential for improving rural public transit service.”
– Sarah Brodt Lenz, Program Administrator, Mn/DOT Office of Transit
Developing Improved Test Rolling Methods for Roadway Embankment Construction
As part of an effort to improve test rolling equipment and specifications, investigators used models and simulations to study soil-wheel interaction, and conducted field and laboratory tests to develop theories linking wheel sinkage to soil mechanical properties.
“For a host of reasons, the old test roller system was no longer sustainable. This study served to better define the soil mechanics related to the new system we are building.”
– John Siekmeier, Mn/DOT Senior Research Engineer
Effects of Center-Line Rumble Strips on Non-Conventional Vehicles
This research considered the safety impacts of centerline rumble strips on motorcyclist safety and behavior. After reviewing accident data and observing cyclist behavior on the highways and in a closed course, investigators concluded that the strips present no safety hazard to motorcyclists.
“We want to establish a policy for where to use centerline rumble strips, so we hired a researcher to investigate the safety impacts of what we have installed.”
– Dave Engstrom, State Traffic Engineer, Mn/DOT Office of Traffic, Security & Operations
Asphalt Pavement Rehabilitation
Decision Tree for Choosing the Optimal Asphalt Pavement Rehabilitation Method
Researchers developed a decision tree for choosing among three common methods of rehabilitating asphalt roads: full depth reclamation, cold-in-place recycling, and mill and overlay. The project report also describes best practices for each of these three rehabilitation techniques.
“The study provides an excellent tool for county and city engineers to use when deciding which type of rehabilitation techniques to implement.”
– Shongtao Dai, MnROAD Research Operations Engineer
Public Land Survey Records
An Inventory of the Public Land Survey Records for Minnesota: The Special Instructions
Investigators located and categorized letters sent to the surveyors who ran public land survey lines and established corner monuments in Minnesota during the 1800s, describing how they should carry out their contracted work. These records, now located in archives in Iowa, Minnesota and Washington, D.C., are of great value to modern surveyors and can be digitally photographed to create a comprehensive Web-based resource.
“Electronic access to these vitally important documents that address land title and boundary definition will enhance the efficiency and effectiveness of land surveyors and those dependent on them while also working to improve the integrity of Minnesota’s vital legal framework for real property.”
Investigation of Winter Pavement Tenting
Researchers studied factors that local engineers believed to cause winter pavement tenting, as well as maintenance strategies for remedying tenting. Based on a literature review, a survey of road engineers in Minnesota and field research, investigators confirmed that deicing chemicals and sands contribute to tenting, and that sealing cracks can reduce its frequency and severity.
“Our field measurements show that crack sealing was an effective treatment for tented roads. I believe sealing should be done as early as possible to reduce accumulation of distress.”
– Eddie Johnson, Research Project Engineer, Mn/DOT Materials and Road Research
Evaluation of Paving Fabrics for Isolation of Bituminous Cracking
Makers of pavement fabrics claim that the products can dramatically extend the service lives of overlays without requiring expensive milling and replacing. This study into the impacts of spun-glass paving fabrics in pavement sections scheduled for structural overlays found little performance benefit from these fabrics.
“Spun-glass paving fabrics did not appear to significantly retard transverse and longitudinal cracks. Historically, paving fabrics have not performed very well in this environment. I do not think there will ever be a fabric effective for this kind of application.”
– Lou Tasa, Mn/DOT District State Aid Engineer
Compaction Remediation for Construction Sites
Machinery passing over the right of way during highway construction results in severe soil compaction, which complicates storm water management and requires the purchase of additional land for retaining ponds. Researchers used deep tilling on a variety of soils with different plow types over two growing seasons. Deep tilling proved to be an ROW rehabilitation method.
“Sometimes the ground was so hard you couldn’t pound a nail in it.”
– Dwayne Stenlund, Natural Resource Specialist and Senior Ecologist, Mn/DOT Environmental Services
Bridge Management Software
Putting Research into Practice: Creating a New Bridge Information Management Tool
Access to bridge data is essential to the effective management of the state’s bridges. The Bridge Hydraulic Information database, an interactive, GIS-based application, was launched in late 2002 to allow users to display bridge hydraulic information from Trunk Highway and State Aid structures using a static database of bridge information. The new Bridge Tool, derived from this database, provides authorized users with more data about the state’s bridges; displays it on maps; and generates reports from Pontis, the state’s bridge management system.
“Users told us they wanted to see more than just bridge hydraulic information, and they wanted to see it all laid out on a map. The new Bridge Tool does just that.”
– Petra DeWall, Assistant State Hydraulics Engineer, Mn/DOT Office of Bridges and Structures
Putting Research into Practice: Resource for Implementing a Street Sweeping Best Practice
This project synthesized recent street sweeping research to create four information sheets and a PowerPoint presentation about street sweeping best practices. These resources cover street sweeping practices, available technologies and their suitability to local needs.
“Local agencies often lack the budget to effectively address every need, requiring them to find a machine that can best fulfill their most pressing needs most efficiently. This project helps in making those choices.”
– Tom Colbert, Director of Public Works, City of Eagan, Minnesota
Putting Research into Practice: Training Module for Pavement Rehabilitation Selection
This six-hour training workshop leads engineers through the process of determining a pavement rehabilitation approach. Steps include pavement assessment, survey of rehabilitation techniques and decision making.
“This new workshop helps city and county engineers by streamlining the process of determining what rehabilitation methods best suit pavement or sidewalk repair.”
– Michael Sheehan, County Engineer, Olmsted County
Rural Road Safety
Putting Research into Practice: Rural Road Safety Solutions Workshop Materials
This project developed a half-day train-the-trainer workshop and associated educational materials summarizing the latest technologies and techniques most suitable for implementing safety improvements on the local transportation system.
“We wanted participants to come away from the workshop looking at highway safety entirely differently, in terms of low-cost solutions focusing on the most critical causes of rural roadway fatalities.”
– Dave Engstrom, Workshop Instructor and State Traffic Safety Engineer, Mn/DOT Office of Traffic, Safety and Operations
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