2006 Reports and Technical Summaries
Balancing Transit and Roadway Investment to Meet Twin Cities Travel Demand
Full Report: 2006-44
Researchers examined the potential for different combinations of transit and roadway expansion to cost-effectively solve the growing problem of traffic congestion on freeways and expressways in the Minneapolis-St. Paul metropolitan area. They found that a critical factor in the solution is the level of service desired for the roadways.
Water Quality Performance of Dry Detention Ponds with Under-Drains
Investigators monitored the performance of three dry detention ponds regarding the amount of suspended solids and phosphorus left behind after storm water drained through them. These storm water management devices performed adequately compared to national standards
The Effect of Rumble Strips on Drivers Approaching Rural, Stop-Controlled Intersections
Researchers studied the stopping patterns of approximately 400 cars, trucks and other vehicles at selected rural intersections and found that in-lane rumble strips caused drivers to reduce speeds earlier and to a greater degree than at intersections without rumble strips. This was the third in a comprehensive series of studies on the effectiveness of in-lane rumble strips.
Developing ITS to Serve Diverse Populations
Full Report: 2006-41 (PDF, 13 MB, 348 pages)
In 2003, the State and Local Policy Program (SLPP) at the University of Minnesota's Humphrey Institute of Public Affairs began research into how Intelligent Transportation System (ITS) technologies can be used to deliver transportation services to an increasingly diverse population in Minnesota. The research objective was to identify the nature of the gap between the emerging needs and existing services, and to propose ways of using technology to bridge the gap, both in terms of providing better transportation options and in reducing the cost of these options. Using the information obtained from emerging demographic data, the 2003 study focused on identifying transportation challenges and opportunities for several different populations, with a particular focus on those that do not or cannot drive. This project continues this general theme through a series of analyses of ITS applications that appear most promising to improve mobility and access for Minnesota's increasingly diverse population. These applications include technologically advanced Community-Based Transit, Car Sharing, use of ITS to implement Value Pricing through conversion of an HOV lane to a High-Occupancy/Toll (HOT) lane, and evaluation of web-based Advanced Traveler Information Systems (ATIS).
Load Rating of Composite Steel Curved I-Girder Bridges Through Load Testing with Heavy Trucks
Researchers investigated the behavior and load rating of a curved I-girder bridge by load testing the bridge and comparing the results with a grillage-based analysis model. They studied model parameters using the results of the tested bridge and two others tested elsewhere to assess the robustness of grillage analysis for load rating this type of bridge.
Mileage-Based User Fee Demonstration Project
The Federal Highway Administration and the Minnesota Department of Transportation co-sponsored a demonstration to test how consumers would change their driving behavior if some of the fixed costs of owning and operating a car were to be converted to variable costs. One hundred and thirty participants were given devices that recorded mileage and time of travel. Prices per mile were assigned randomly to each participant, ranging from 5 cents per mile to 25 cents per mile. The findings indicate that per mile pricing does result in measurable, but small reductions in driving. The largest effect is on weekend driving and on peak weekday travel (as some participants were able to substitute mass transit for their vehicle). One key finding in this experiment is that those households that are willing to change their driving behavior will do so with low per mile cost incentives. On the other hand it was also determined that those households unable to change their behavior do not do so even under relatively higher cost incentives. Therefore, the marginal effect of per mile prices seems to drop off dramatically after some point in the lower range of prices.
Minnesota Value Pricing Outreach and Education
Full Report: 2006-38 (PDF, 17 MB, 379 pages)
The State and Local Policy Program (SLPP) of the Humphrey Institute of Public Affairs, University of Minnesota, in partnership with the Minnesota Department of Transportation (Mn/DOT) and the Metropolitan Council originally designed a project that envisioned extensive research, outreach, and education activities leading to identification and support for a demonstration project by the end of the three year project period. With early acceptance and support for the I-394 MnPASS project by the Governor and Legislature, the Humphrey Institute in collaboration with the Minnesota Department of Transportation and the Federal Highway Administration revised the project to focus on research, outreach, and education activities focused specifically on the I-394 MnPASS project. The major findings of this project are detailed in the summary and supported by the appendices. The appendices include multiple papers submitted to the Transportation Research Board, final reports from the first two waves of the longitudinal panel survey, the community task force report, and an information booklet designed to quickly educate lawmakers.
Application of Precast Decks and Other Elements to Bridge Structures
Full Report: 2006-37 (PDF, 6 MB, 271 pages)
A number of countries have incorporated precast components in bridge superstructures and substructures. Precast components include deck, abutment, and wall elements. Benefits of using precast elements in bridge construction include the high level of quality control that can be achieved in plant cast production compared to field cast operations and speed of construction afforded by the assembly of precast elements at the site rather than the time consuming on site forming and casting required in cast-in-place construction. Key components in the application of precast concrete to bridge structures are the connection elements. Connection details include the use of post-tensioning systems, and various connection details such as weld plates, studs in grout pockets, and shear keys. The Minnesota Department of Transportation (Mn/DOT) constructed a bridge incorporating precast elements to enable rapid construction. The objective of this study was to develop an instrumentation plan to enable investigation of the performance of this bridge. Researchers developed an instrumentation plan based on information provided by the Mn/DOT bridge office regarding the specific bridge details and behaviors to be investigated. The instrumentation plan included the types and locations of the instruments.
Beyond Business as Usual: Ensuring the Network We Want Is the Network We Get
Researchers documented construction decision rules and performance measures, and then used these to compare computer models of alternative future states of the highway network. The models showed whether changing current construction decision practices will produce a better network. Researchers concluded that changing decision rules had little effect as compared to increasing the overall investment level.
Safety Impacts of Street Lighting at Isolated Rural Intersections
Investigators quantified the effectiveness of roadway lighting as a tool for reducing nighttime crashes at isolated rural intersections. Based on positive results, the researchers recommended that MnDOT consider revising its lighting guidelines to apply to a higher percentage of rural intersections, provide quantifiable volume and crash measurements, and consider roadway functional classification.
Putting Research into Practice: Minnesota Seal Coat Handbook 2006
This project updated the extremely popular 1998 handbook and created an accompanying training module in light of recent Mn/DOT seal coating studies, specifications and field experience. The updated handbook covers additional seal coat uses such as fog sealing to rejuvenate pavements and chip sealing on recreational trails.
Review of Michigan's Rural Intersection Crashes: Application of Methodology for Identifying Intersections for Intersection Decision Support (IDS)
Full Report: 2006-33 (PDF, 3 MB, 58 pages)
The objective of the Intersection Decision Support (IDS) research project, sponsored by a consortium of states (Minnesota, California, and Virginia) and the Federal Highway Administration (FHWA), is to improve intersection safety. The Minnesota team's focus is to develop a better understanding of the causes of crashes at rural unsignalized intersections and then develop a technology solution to address the cause(s). In the original study, a review of Minnesota's rural crash records and of past research identified poor driver gap selection as a major contributing cause of rural intersection crashes. Consequently, the design of the rural IDS technology has focused on enhancing the driver's ability to successfully negotiate rural intersections by communicating information about the available gaps in the traffic stream to the driver. In order to develop an IDS technology that has the potential to be nationally deployed, the regional differences at rural intersections must first be understood. Only then can a universal solution be designed and evaluated. To achieve this goal of national consensus and deployment, the University of Minnesota and the Minnesota Department of Transportation initiated a State Pooled Fund study, in which nine states are cooperating in intersection-crash research. This report documents the crash analysis phase of the pooled fund study for the State of Michigan, culminating in a recommendation of an intersection for instrumentation. The driver gap acceptance behavior data to be collected at the selected intersection will feed into the Cooperative Intersection Collision Avoidance System (CICAS) Stop Sign Assist Program.
Review of North Carolina's Rural Intersection Crashes: Application of Methodology for Identifying Intersections for Intersection Decision Support
Full Report: 2006-32 (PDF, 2 MB, 56 pages)
The objective of the Intersection Decision Support (IDS) research project, sponsored by a consortium of states (Minnesota, California, and Virginia) and the Federal Highway Administration (FHWA), is to improve intersection safety. The Minnesota team's focus is to develop a better understanding of the causes of crashes at rural unsignalized intersections and then develop a technology solution to address the cause(s). In the original study, a review of Minnesota's rural crash records and of past research identified poor driver gap selection as a major contributing cause of rural intersection crashes. Consequently, the design of the rural IDS technology has focused on enhancing the driver's ability to successfully negotiate rural intersections by communicating information about the available gaps in the traffic stream to the driver. In order to develop an IDS technology that has the potential to be nationally deployed, the regional differences at rural intersections must first be understood. Only then can a universal solution be designed and evaluated. To achieve this goal of national consensus and deployment, the University of Minnesota and the Minnesota Department of Transportation initiated a State Pooled Fund study, in which nine states are cooperating in intersection-crash research. This report documents the crash analysis phase of the pooled fund study for the State of North Carolina, culminating in a recommendation of an intersection for instrumentation. The driver gap acceptance behavior data to be collected at the selected intersection will feed into the Cooperative Intersection Collision Avoidance System (CICAS) Stop Sign Assist Program.
Putting Research into Practice: Field Handbook for Concrete Repair for Local Streets and County Roads
Technical Summary: 200631TS
Handbook: 2006-31 "Field Handbook for Concrete Repair for Local Streets and County Roads"
Investigators drew on county expertise and MnDOT specifications to create a streamlined field handbook and accompanying training that present standard plates and step-by-step design and construction guidance for use on low-volume concrete roads, sidewalks, and curbs and gutters.
Feasibility Study of Portable Weight-in-Motion Systems for Highway Speed
Full Report: 2006-30 (PDF, 133 KB, 23 pages)
Minnesota Department of Transportation (Mn/DOT) needs improved traffic monitoring tools to optimally allocate road maintenance and improvement resources. In particular, the department needs a method of including vehicle and axle weights with portable traffic logging equipment. The cost of existing Weigh-in-Motion (WIM) equipment prevents widespread use in locations where only temporary monitoring is needed. This project was a survey of the suppliers of portable WIM systems, allowing a few systems to be moved between locations of interest. There were four candidate systems found and studied, of which two are recommended for further evaluation. Both systems appear to meet the needs Mn/DOT established and local testing will allow a final decision on their suitability.
Improving the Ability of Drivers to Avoid Collisions With Snowplows in Fog and Snow
Full Report: 2006-29 (PDF, 455 KB, 33 pages)
The goal of this work is to understand how the processing of motion under the conditions created by blowing snow causes drivers to fail to detect that they are approaching a vehicle ahead. Color was examined under blowing snow conditions to assess whether an equiluminant (equal brightness) situation was created. In this situation, contrast in light level is not detected but differences in color are. When an equilument situation is created by snow, a perceptual illusion lowers the ability to perceive approach. The results indicate that colors in the red-yellow part of the spectrum can create a dangerous equiluminant situation in blowing snow and fog. We were unable to find an optimum color to paint snowplows to make them less susceptible to rear-end collisions. Perception studies investigated the ability of the visual system to detect the expansion pattern that drivers use to perceive that they are approaching a vehicle. We found that low contrast created by a snow cloud greatly reduces the ability to perceive approach. Flashing lights that increase conspicuity, substantially decreased the chances that a driver will be able to avoid a crash. Additional ways to improve the placement of warning lights based on these findings were proposed.
Chemical Inventory and Database Development for Recycled Material Substitutes
Full Report: 2006-28 (PDF, 593 KB, 149 pages)
Mn/DOT engineers are increasingly looking to recycled materials as readily available and cost-effective substitutes for natural aggregate and to fly ash as a material that can be used in the stabilization of sub-base soils. These recycled wastes have the potenial to contain unacceptably high levels of some chemicals. This project produced chemical data on wastes, non-surface background soils, and natural aggregates for use in a due diligence screening tool in current service by Mn/DOT and developed by the Office of Environmental Services (OES). These data will be used by OES for their internal Mn/DOT due diligence determinations using their streamlined hazard evaluation process. A future Local Road Research Board project will transform the OES streamlined hazard evaluation process into a CD-based product for use by the larger transportation community. Data developed by this current project will be used to populate the future CD-based product electronic database. This project will maintain consistency with the current in use Office of Environmental Services (OES) streamlined hazard evaluation process for waste recycling in Mn/DOT infrastructure projects.
Erosion Risk Assessment Tool For Construction Sites
Full Report: 2006-27 (PDF, 587 KB, 72 pages)
The impact of erosion and sediment from construction sites can be reduced by using a variety of onsite and offsite practices. The WATER model was developed to be a tool to assess the effectiveness of different sediment control practices. The WATER model evaluates risk by performing many simulations of a construction site response for different weather conditions. A particularly important component of the WATER model is the prediction of daily climate variables and storm characteristics called WINDS. This model uses the statistics for the analyzed data to predict many years of possible weather conditions. Predicted weather and storm characteristics are in very good agreement with those observed. The WATER model simulates surface runoff, plant processes, and erosion and sediment transport as major hillslope processes. Four runoff events (spring dry run, spring wet run, fall dry run, and fall wet run) from artificial rainfall conditions were measured.
Moisture Effects on PVD and DCP Measurements
Full Report: 2006-26 (PDF, 83 MB, 549 pages)
This study deals with the experimental investigation of the effects of moisture and density on the elastic moduli and strength of four subgrade soils generally representing the range of road conditions in Minnesota. The testing approach involved i) reduced-scale simulation of field compaction, ii) field-type testing on prismatic soil volumes, and iii) element testing on cylindrical soil specimens. The field-type testing included: i) the GeoGauge, ii) the PRIMA 100 device, iii) the modified light weight deflectometer (LWD) device, iv) the portable vibratory deflectometer (PVD) and v) the Dynamic Cone Penetrometer (DCP). To compare the Young's modulus values stemming from the field-type and laboratory experiments, cylindrical specimens were extracted from the prismatic soil volumes and tested for the resilient modulus (Mr), small-strain Young's modulus using bender elements. The results reveal that both moisture and density have a measurable effect on the elastic modulus and strength of all four soils. On the element testing side, the small strain estimates from the bender element tests were in good agreement with the resilient modulus values. In the context of field testing, there was significant scatter of the estimated Young's moduli depending upon the particular testing device.
Improving Road Safety with Two-Way Left-Turn Lanes
Researchers examined the effect on safety and operations of converting traditional four-lane roadways to three-lane roadways with two-way left-turn lanes by analyzing before and after data from nine Minnesota sites. They found that such conversions can improve safety with little impact on operational conditions.
Putting Research into Practice: Managing Conflicts Arising from Public Involvement in Transportation Projects
Investigators conducted interviews to refine a previously established system for categorizing and addressing conflicts with the public that arise during transportation projects. They then created a document to implement this system for use in the new version of Mn/DOT's public involvement manual.
Urbanization of Minnesota's Countryside, 2000-2025: Evolving Geographies and Transporation Impacts
Full Report: 2006-23 (PDF, 3.3 MB, 256 pages)
In this study, we examine population and housing change, changes in industrial activity and occupational changes, and characteristics of commuters and the journey to work for those working away from home in 26 regional centers and their commute sheds in Greater Minnesota. We also explore ways in which Public Use Microdata Samples (PUMS) and Public Use Microdata Areas (PUMAs) might be exploited to shed additional insight into the changing nature of the demographic, economic and commuting patterns that are now pervasive throughout Greater Minnesota. These data are evaluated to explore links between demographic and economic features of working-age populations, and relationships between worker and household characteristics and aspects of commuting activity on the other. The final chapter examines regional economic vitality and travel behavior across the Minnesota Countryside. When population change in sample regional centers in the 1990s is compared with change in the nearby counties that comprise the centers' commuting fields, four situations appear: those where centers and their commuting fields both had population increases; centers with declining populations, but increases in the commuting fields; centers with growing populations, but with declines in their commuting fields; and situations where both the center and the commute field lost population.
Development of Efficient Integrated Data Archival/Retrieval Model for R/WIS, RTMS, and Loop Traffic Data
Full Report: 2006-22 (PDF, 1.1 MB, 59 pages)
This report describes a new data warehouse model developed for integrating Road Weather Information System (R/WIS) and traffic data and the prototype implemented. The building blocks of the prototype include data aggregation methods from sensors, a data archiving system, and multi-user data access and retrieval environments through a network. This new data warehouse model seamlessly integrates the heterogeneous nature of R/WIS and traffic data. The key to this data model was utilization of a network storage model referred to as a parallel First-In-First-Out (FIFO) data storage where various sensor data are deposited as they are aggregated while different types of data-consuming modules obtain data without an explicit protocol requirement. For the prototype implementation, four different data aggregation methods from traffic and R/WIS sources were used to demonstrate that diverse data types and collection methods could be seamlessly integrated together. As an application of this data warehouse, weather impact on traffic flow was studied by retrieving traffic data under various atmospheric and pavement conditions, and the results are included. It was noticed that R/WIS provides a significant advantage over the traditional National Weather Service data in learning detailed location specific weather and pavement conditions from which weather impact on traffic flow could be accurately analyzed.
Contraflow Transportation Network Reconfiguration for Evacuation Route Planning
Full Report: 2006-21 (PDF, 1,000 KB, 48 pages)
Given a transportation network having source nodes with evacuees and destination nodes, we want to find a contraflow network configuration, i.e., ideal direction for each edge, to minimize evacuation time. Contraflow is considered a potential remedy to reduce congestion during evacuations in the context of homeland security and natural disasters (e.g., hurricanes). This problem is computationally challenging because of the very large search space and the expensive calculation of evacuation time on a given network. To our knowledge, this paper presents the first macroscopic approaches for the solution of contraflow network reconfiguration incorporating road capacity constraints, multiple sources, congestion factor, and scalability. We formally define the contraflow problem based on graph theory and provide a framework of computational structure to classify our approaches. A Greedy heuristic is designed to produce high quality solutions with significant performance. A Bottleneck Relief heuristic is developed to deal with large numbers of evacuees. We evaluate the proposed approaches both analytically and experimentally using real world datasets. Experimental results show that our contraflow approaches can reduce evacuation time by 40% or more.
Validation of DCP and LWD Moisture Specifications for Granular Materials
Full Report: 2006-20
Advances in technology have produced a new generation of in situ soil testing devices. Implementation of quality assurance procedures that make use of these devices would improve test precision, increase inspector efficiency and safety, and allow for the direct verification of values used in mechanistic design procedures. During this study, the dynamic cone penetrometer (DCP) and light weight deflectometer (LWD) were used on laboratory prepared specimens. It was found that the Mn/DOT DCP specification accurately assessed compaction quality, although there were some suggestions for improvement. This study reached the following conclusions and recommendations. The DCP penetration should continue until the cone passes through the subbase lift of interest. The DCP seating requirement serves little purpose for a subbase lift that will be covered by subsequent lifts. The acceptable range of moisture contents during DCP testing of granular subbase should be capped at 10%. A sufficient amount of data exists to create an LWD trial specification for granular subbase. A mass of 10 kg, drop height of 50 cm, and plate diameter of 20 cm are recommended. It is also recommended that the LWD specification include three seating drops followed by three data drops at each new height.
Full Report: 2006-19
Much of the benefit of an underbody scraper lies in the ability to apply high levels of pressure to break up compacted ice and snow. However, this also leads to increased wear on the underbody's cutting edges and frequent replacement. This process is time and labor intensive and can often lead to a wide variety of injuries. Accordingly, the Quick Edge Rapid Underbody Cutting Edge Changing System was designed to simplify this difficult process and remove some of the risk involved. This report outlines the steps taken in creating the final working design and prototype.
Construction Report for MnROAD Thin Whitetopping Test Cells 60-63
Full Report: 2006-18 (PDF, 1 MB, 103 pages)
After seven years of heavy traffic and weathering, three ultra-thin whitetopping test cells on the interstate portion of the Minnesota Road Research project (MnROAD) had reached terminal serviceability. Those three test cells were replaced by four new thin-whitetopping test cells in October 2004. This report describes the physical characteristics of the new whitetopping test cells 60-63. The report also summarizes the results from the material tests and curl and warp measurements taken during, and immediately following, construction of the test cells.
Local Road Tax Options: Is Minnesota Really That Different?
Full Report: 2006-17 (PDF, 177 KB, 33 pages)
Local governments in the U.S. use a variety of tax mechanisms to fund local roads. Twelve options are examined in this report related to property access, vehicle use or local economic activity. The most frequent local levies are property taxes, special assessments, vehicle registration taxes, motor fuel taxes and local sales taxes. The overall mix of local road funding also varies widely by state and region. Nebraska, Wisconsin and Kansas have local road revenues most like Minnesota, while local roads funding in New Hampshire, Florida and Nevada is the least similar. The benefits of any individual road tax must be judged in the context of the larger state and local tax system.
Access to Destinations: Development of Accessibility Measures
Full Report: 2006-16 (PDF, 7.8 MB, 125 pages)
Transportation systems are designed to help people participate in activities distributed over space and time. Accessibility indicates the collective performance of land use and transportation systems and determines how well that complex system serves its residents. This research project comprises three main tasks. The first task reviews the literature on accessibility and its performance measures with an emphasis on measures that planners and decision makers can understand and replicate. The second task identifies the appropriate measures of accessibility, where accessibility measures are evaluated in terms of ease of understanding, accuracy and complexity, while the third task illustrates these accessibility measures. During this process a new accessibility measure named Place Rank is introduced as an accurate measure of accessibility. In addition, several previously-defined accessibility measures are reviewed and demonstrated in this report including Cumulative opportunity and gravity-based measures. The gravity-based measure is widely used in the literature yet cumulative opportunity tends to be easier to understand and interpret by the public, planners, and administrators. A major contribution of this research is the comparison of accessibility measures over time and among various modes. Effects of accessibility on home sales are also tested. Homebuyers pay a premium to live near jobs and away from competing workers. Accessibility promises to be a useful tool for monitoring the land use and transportation system, and assessing and valuing the benefits of proposed changes to either land use or networks.
Investigation of the Low-Temperature Fracture Properties of Three MnROAD Asphalt Mixtures
Full Report: 2006-15 (PDF, 822 KB, 74 pages)
In this research effort, field cores were taken from cells 33, 34 and 35 at the MnROAD facility to determine the fracture properties of the field mixtures, to compare them with the laboratory-prepared mixtures analyzed in a previous study, and to evaluate the effect of aging at different depths in the asphalt layer. In addition, the properties of the recovered binders from the field cores as well as the properties of the original binders aged in laboratory conditions were investigated. The test results and the analyses performed indicate that the fracture tests performed on asphalt binders and asphalt mixtures have the potential to predict the field performance of asphalt pavements with respect to thermal cracking. The binder results confirm the predictions of the current performance grading system; however, it appears that the fracture resistance of the PG-34 asphalt mixture is better than the fracture resistance of the PG-40 mixtures, which is the opposite of what the PG system predicts.
Streamlining of the Traffic Modeling Process for Implementation in the Twin Cities Freeway Network - Phase II
Full Report: 2006-14 (PDF, 1.4 MB, 66 pages)
Comprehensive methodologies are proposed for improving the quality of both freeway and arterial intersections traffic volumes for the purpose of enabling and improving traffic simulations. Specifically, established and enhanced procedures for checking and correcting freeway temporal errors are integrated with an optimization-based algorithm for reconciling spatial inconsistencies in freeway traffic counts. In addition to this, an empirical methodology is further integrated to balance arterial intersection traffic counts. The proposed methodologies have been successfully automated and implemented as two computer programs, i.e., TradaX for processing freeway volume and ArtBaT for arterial intersection traffic counts. Initial evaluations of these tools suggest that they have the potential of reducing total modeling time by 25% ~ 30%, while resulting in improved calibration of simulation models, more reliable analysis, and better use of staff resources for meeting project deadlines.
Intelligent Compaction and In-Situ Testing at Mn/DOT TH53
Full Report: 2006-13 (PDF, 2 MB, 50 pages)
This report describes an intelligent compaction demonstration project on Mn/DOT TH 53 in Duluth, MN, and the associated field and laboratory testing. The project was conducted during September 2005, using a Caterpillar Model CS-563E vibratory soil compactor, equipped with Intelligent Compaction (both Compaction Meter Value (CMV) and energy or power) and global positioning system (GPS) technology. A Prima light-weight deflectometer (LWD), dynamic cone penetrometer (DCP) and Humboldt GeoGauge were used to collect in situ companion test data at 42 locations. Mn/DOT conducted gradation, moisture content and Procter tests. Location and Compaction Meter Value (CMV) were downloaded for comparison with the in situ testing. CMV data was compared to the in situ data on a point-by-point basis and on the basis of the overall distribution. In general, poor correlations were obtained on a point-by-point basis, likely due to the depth and stress dependency of soil modulus, and the heterogeneity of the soils. Good correlations were obtained between CMV values and DCP measurements for depths between 8-inches and 16-inches deep. The Caterpillar Compaction Viewer software, although still in development at the time of testing, is functional and is well integrated with GPS. It is easy to extract data and do more sophisticated analyses. Surface-covering documentation adds value by identifying potential problem areas where compaction is limited by material, moisture or subgrade deficiencies. LWD testing protocol must be followed to obtain useful results, since measurements vary significantly between successive tests. Relatively good correlations were obtained between LWD and GeoGauge. The GPS technology used for the demonstration is not adequate to distinguish between lifts.
Duration of Spring-Thaw Recovery for Aggregate-Surfaced Roads
Full Report: 2006-12 (PDF, 2 MB, 289 pages)
Low-volume roads constructed in regions susceptible to freezing and thawing periods are often at risk of load-related damage during the spring-thaw period. The reduced support capacity during the thawing period is a result of excess melt water that becomes trapped above the underlying frozen layers. Many agencies place spring load restrictions (SLR) during the thaw period to reduce unnecessary damage to the roadways. The period of SLR set forth by the Minnesota Department of Transportation is effective for all flexible pavements; however, experience suggests that many aggregate-surfaced roads require additional time relative to flexible pavements to recover strength sufficient to carry unrestricted loads. An investigation was performed to improve local agencies' ability to evaluate the duration of SLR on aggregate-surfaced roadways. This was accomplished through seasonal measurements of in-situ shear strengths, measured using the dynamic cone penetrometer (DCP), on various Minnesota county routes. In-situ strength tests were conducted on selected county gravel roads over the course of three years. Strength levels recorded during the spring-thaw weakened period were compared to fully recovered periods that typically occur in late spring/summer. The results indicate that aggregate-surfaced roads generally require 1 to 3 additional weeks, over that of flexible pavements, to reach recovered bearing capacity. Additionally, a strong correlation was found between duration required to attain given strength recovery values and climatic and grading inputs.
Development of a Trash Harvester for Mn/DOT - Phase 1
Full Report: 2006-11 (PDF, 78 MB, 57 pages)
The purpose of this project is to mechanize the trash collection process. There are machines available to remove trash on smooth surfaces such as concrete, but none of them are able to pick-up litter on grassy areas. The objective of this study is to design and build a machine to collect trash and litter (such as papers, plastic bags, bottles, aluminum cans, etc) lying on grassy areas alongside a road. A "Trash Harvester" would make the process easier, safer, faster, and more economical.
Review of Wisconsin's Rural Intersection Crashes: Application of Methodology for Indentifying Intersections for Intersection Decision Support (IDS)
Full Report: 2006-10 (PDF, 1.8 MB, 59 pages)
The Intersection Decision Support (IDS) research project is sponsored by a consortium of states (Minnesota, California, and Virginia) and the Federal Highway Administration (FHWA) whose objective is to improve intersection safety. The Minnesota team's focus is to develop a better understanding of the causes of crashes at rural unsignalized intersections and then develop a technology solution to address the cause(s). In the original study, a review of Minnesota's rural crash records and of past research identified poor driver gap selection as a major contributing cause of rural intersection crashes. Consequently, the design of the rural IDS technology has focused on enhancing the driver's ability to successfully negotiate rural intersections by communicating information about the available gaps in the traffic stream to the driver. In order to develop an IDS technology that has the potential to be nationally deployed, the regional differences at rural intersections must first be understood. Only then can a universal solution be designed and evaluated. To achieve this goal of national consensus and deployment, the University of Minnesota and the Minnesota Department of Transportation initiated a State Pooled Fund study, in which nine states are cooperating in intersection-crash research. This report documents the crash analysis phase of the pooled fund study for the State of Wisconsin.
Performance Effectiveness of Design-Build, Lane Rental, and A + B Contracting Techniques
Full Report: 2006-09 (PDF, 346 KB, 95 pages)
Experimentation with innovative contracting methods over the last several years has produced several techniques recently formally approved for use by the Federal Highway Administration. While the FHWA has recognized and defined many standard practices for innovative contracting, the need has arisen to compare the effectiveness of different innovative contracting methods to each other. Performance and cost and value implications of A+B contracts, design-build contracts, lane rental contracts, and traditional contracts were investigated. Specific performance and cost measures considered are Administration Costs, Project Costs, Management Complexity, Disruption to Third Parties, RUC, Innovation, Product/Process Quality, and Funding Flexibility. Performance parameters are compared on nine different project types; the methodology utilized a survey of national experts who rated each innovative contracting method for each performance factor on each of the project types. This study resulted in fifteen recommendations for improving management practices in the use of innovative contracting for transportation projects. These recommendations are also intended to assist the Minnesota Department of Transportation in determining which contract method is likely to be most effective given certain project criteria and construction options and to determine directions for future research, particularly on emerging methods such as design-sequencing and A + B + C contracting.
North/West Passage Transportation Pooled Fund Program - Phase I
Full Report: 2006-08
The North/West Passage Transportation Pooled Fund (TPF) Program is a multi-state cooperative program for the coordination, development, and deployment of Intelligent Transportation Systems projects along I-90 and I-94 from the states of Wisconsin to Washington. Individual states along the corridor have developed different systems for collecting, processing and integrating traveler and road maintenance information, and for delivering this information to users. As a result traveler information along the corridor has not been seamless or readily integrated and shared across borders. The objective of this TPF Study Phase I was to influence ongoing standards development; and utilize effective methods for coordinating, integrating, and sharing of traveler information across borders. The Minnesota Department of Transportation (DOT) was the lead agency for this study with North Dakota DOT and Wisconsin DOT also contributing funding for Phase I. A Steering Committee, consisting of members from the eight corridor states (Washington, Idaho, Wyoming, Montana, North Dakota, South Dakota, Minnesota, and Wisconsin), met monthly to coordinate efforts. The Federal Highway Administration served as a monitoring body, providing strategic and technical input. The committee successfully completed eight Phase I corridor projects and approved a Phase II Work Plan focusing on a corridor strategic plan.
Fatigue-Resistant Design for Overhead Signs, Mast-Arm Signal Poles, and Lighting Standards
Full Report: 2006-07 (PDF, 3.3 MB, 190 pages)
Traffic signs and signals are often supported by flexible cantilevered structures that are susceptible to wind-induced vibration and fatigue. The latest version of the design specifications published by the American Association of State Transportation Officials (AASHTO) now considers fatigue as a limit state. However, most of the fatigue classifications for welded details were not based on full-scale testing, and are thought to be overly conservative. This research will address the fatigue resistance of two common mast arm-to-pole connections used in the state of Minnesota. The resistance attained experimentally aligned with current predictions using AASHTO procedures, except for in-plane loading of box connection details. As a consequence of specimen design, a variety of tube-to-transverse plate connections were also tested using multi-sided tube cross-sections with different tube diameters, tube thicknesses, as well as base plate thicknesses. The standard tube-to-transverse plate connection exhibited Category K2 resistance, two categories lower than the E specified by AASHTO. This resistance was enhanced to Category E through impact treatment or Category E by doubling the base plate thickness. Gusset plates could not prevent cracking of the tube at the base plate, but the tips of the gusset plate exhibited Category E resistance.
Blind Deconvolution of Vehicle Inductance Signatures for Travel-Time Estimation
Full Report: 2006-06 (PDF, 1.3 MB, 64 pages)
Travel-time data provides vital information for traffic monitoring, management, and planning. The objective of this research was to develop a new computational approach to accurately measure travel time from two sets of spatially separated loop detectors using re-identification of vehicle inductance signatures generated by the loops. In order to restore lost details from the raw inductance waveforms, the author modeled the output of the loop detectors as a convolution of the original vehicle signature and the loop system function. To solve this blind problem, two basic blind deconvolution approaches were used. The first estimates the loop system function using a speed estimate obtained from the inductance waveform. The second approach is an adaptive iterative method referred to as the Godard blind deconvolution. Experimental results showed that both methods performed well and significantly exposed the original signature information with unique vehicle characteristics.
A Nonlinear State Space Approach to Arterial Travel Time Prediction
Full Report: 2006-05 (PDF, 1.7 MB, 73 pages)
The study uses time series and the Kalman prediction techniques along with modern technology such as the Global Positioning System (GPS) for accurate data collection and analysis. A greater understanding of travel time will help facilitate traffic system performance monitoring, control, planning, and informed route decisions for motorists accessing information from changeable message sings (CMS). The models used for estimations include the autoregressive integrated moving average (ARIMA) and the autoregressive moving average (ARMA). The study collects travel data for the peak hours of travel (3:30-5:00 p.m.) over an eight-month period on the busiest section of Highway 194 in Duluth, Minnesota. The predictions were conducted over two weeks during the summer of 2005. Observed and predicted travel times are charted carefully and report evaluations determine the success of the study.
Use of Adhesives to Retrofit Out-of-Plane Distortion Induced Fatigue Cracks
Full Report: 2006-04
A field test and large-scale test were conducted. Coupon tests revealed reasonable durability when exposed to room temperature, immersion in water at 65 degrees and 111 degrees, air at -4 degrees, repeated freezing and thawing, outdoor elements, and fire. Thorough investigation of the adhesive after application and then again 3 1/2 years after application provides valuable information on how well the adhesive performed in an outdoor environment with intermittent stresses. The report includes organized data showing durability of the product from every application and use throughout the study period, 3 1/2 years. Detailed instructions on field application were developed and are included in this report.
Statistical Modeling for Intersection Decision Support
Full Report: 2006-03 (PDF, 857 KB, 39 pages)
This project was a component of the Intersection Decision Support (IDS) effort conducted at the University of Minnesota. In this project, statistical modeling was applied to crash data from 198 two-way, stop-controlled, intersections on Minnesota rural expressways, in order to: (1) identify intersections that were plausible candidates for future IDS deployment; (2) develop a method for estimating the crash-reduction effect of IDS deployment; (3) develop a method for predicting the crash-reduction potential of IDS deployment, and (4) test the hypothesis that older drivers were over-represented in intersection crashes along US Trunk Highway 52. All these objectives were accomplished using hierarchical model structures similar to that employed in the Interactive Highway Safety Design Model. Five rural expressway intersections were identified as having crash frequencies that were atypically high, and this group included the intersection of US Trunk Highway 52 and Goodhue County highway 9, the site chosen for the prototype IDS deployment. It was then determined that a 3-year count of crashes after deployment would probably be sufficient to detect any crash reduction effect due to the IDS, although a reliable estimate of the magnitude of this effect would require a longer test period. Assuming that the effect of an IDS deployment would be to make the crash frequencies at treated intersections similar to that experienced by typical intersections, it was estimated that deployment of the IDS at the five high-crash intersections would, over a 15-year period, result in a reduction of about 308 crashes. Finally, using an induced-exposure approach, twelve intersections were identified as showing over-representation of older drivers, five of these being on US Trunk Highway 52.
Bicycle and Pedestrian Toolbox
Full Report: 2006-02 (PDF, 20.8 MB, 38 pages)
This Bicycle and Pedestrian Toolbox provides transportation planners and engineers with information on how to plan and design a bicycle and pedestrian network for a community. This toolbox summarizes each stage involved in the process of designing an active transportation network with a focus on how land use effects transportation planning. The planning is a cyclical six-stage process where first, community values are determined; second, existing features are evaluated; third, desire lines are identified; fourth, phasing of development is defined; fifth, selecting design treatments; and finally, sixth, evaluation of the network based on performance criteria.
Investigation of Deterioration of Stainless Steel Dowel Tubes Under Repeated Loading
Full Report: 2006-01
The Minnesota Department of Transportation (Mn/DOT) has selected a 316L stainless steel schedule 40 pipe as a new dowel bar to be used as a bid alternative for its high performance Portland Cement Concrete (PCC) pavements. Although this dowel bar should provide sufficient shear transfer capacity and low concrete bearing stresses, there was a concern that lack of a solid core may not provide sufficient resistance of the cross-section to distortion under a heavy axle loading. In this study, long-term performance of the 316L stainless steel schedule 40 pipe was investigated by subjecting a doweled joint to accelerated repeated loads through the use of the Minnesota Accelerated Loading Facility (Minne-ALF-2). Assessment of the new dowel bar performance was performed based on comparison with the standard 1.5 inch diameter epoxy -coated round steel dowel. The following tasks were accomplished: redesign, assembly and calibration of new version of Minne-ALF, development of experimental design matrix, conduct of accelerated full-scale testing, and post-testing evaluation. The results from the MinneALF-2 tests illustrated that while the LTE for the stainless steel dowel tubes was lower than the LTE for the epoxy-coated dowels, the stainless steel tubes are capable of providing over 70% LTE in the long-term when installed in concrete pavement joints. The ability to withstand deformation and corrosion while providing sufficient long-term performance suggests that the stainless steel tube dowel is an attractive alternative to the solid epoxy-coated dowel for use in long-life pavements.