2007 Reports and Technical Summaries
Improving Minneapolis/St. Paul's Ramp Metering System for Smoother Traffic Flow
To streamline traffic flow and reduce backups on Twin Cities highways, MnDOT engineers researched ways to improve the algorithm they use to estimate queue size on entrance ramps and calculate minimum rates for releasing cars from ramps to highways. More than 20 parameters were tested through computer simulations. The new optimized algorithm and ramp-monitoring system increases average speed and reduces travel time and energy consumption.
Mileage-Based User Fee Public Opinion Study: Summary Report Phase One (Qualitative)
Full Report: 2007-50
A panel of select key experts expressed their opinion that the fuel tax is viewed as an accepted, efficient option for funding transportation, and that it will continue to be for the next 15 to 20 years. Mileage-based fees are a solution that will likely not be necessary nor feasible for at least 10 years according to the experts. It is imperative that transportation authorities clearly identify the objectives of the mileage-based user fee as a first step for determining structure/design of the concept and how to communicate it. These experts proposed that a mileage-based user fee should be used to supplement, rather than replace, the current motor fuel tax. Focus group participants (n = 10 groups) did not fully grasp the amount of tax dollars they spend per year on the transportation system, nor do they easily recognize the sources through which these monies come. After discussing the current and projected funding shortfalls from the motor fuel tax and hearing a brief description of a usage tax based on mileage, participants were generally comfortable with the idea of paying their fair share based on how much they use the roads. Varying a mileage-based fee based on size and/or weight of the vehicle was seen as logical, and not do so would unfairly penalize those who have chosen to drive fuel-efficient or hybrid vehicles. The congestion pricing model was seen as less fair because it would negatively impacts those drivers who need to travel for work during standard rush hours. These participants were skeptical of the claim that the information would not be tracked, and being watched by Big Brother was mentioned frequently. Many believed that mileage-based user fee technology would be expensive to implement and maintain, and suggested that, if additional funds were needed, simply increase the existing fuel tax or registration fees. As qualitative research, these findings are not projectable to either of the segments researched.
Developing a Computer Program to Select Peak Dynamic Sensor Responses from Pavement Testing
In order to better analyze the vast amounts of pavement response data that Mn/DOT collects, investigators updated and enhanced MnDOT's Peak-Pick software program. The updated version is more robust and efficient, and provides multiple ways to analyze the data.
Driving Performance During 511 Information Retrieval: Cell Phone 2
Full Report: 2007- 48
As a logical and necessary extension of previous research (Rakauskas, et al., 2005), this study aims to assess the risk of cell phone use for traveler information applications; namely while using Minnesota's 511 interactive voice response (IVR) menu. First, detailed usage, utility, and usability evaluations of the MN511 were conducted. The goal of this design was to help harmonize the transfer of knowledge between access methods while also easing implementation concerns for the MN511 developers. Next, a simulated driving experiment was conducted with the goal of seeing if using an IVR menu leads to more risky driving behavior compared to driving while not accessing a menu. It also allowed us to see if changing the MN511 menu might affect driver performance. While using both phone menus, drivers seemed to compensate for the additional mental workload by delaying their reactions until they felt comfortable taking action. There were no differences between the two menu types for the majority of driving performance measures. This study addresses issues with the 511 IVR menus that were identified during this study and presents recommendations for future development.
Shear Capacity of Prestressed Concrete Bridge Girders
Design specifications of shear reinforcement requirements in prestressed concrete bridges have changed significantly. Researchers load-tested to failure a girder that was built to older design codes and evaluated its shear capacity. They also examined how to judge the shear capacity of other bridges designed to older specifications.
Performance Assessment of Underground Stormwater Treatment Devices
Researchers developed a universal method for evaluating the performance of underground stormwater treatment devices in retaining sediment for removal after a storm event. The method was the first of its kind and was endorsed by ASTM.
Development of a PC-Based Eight-Channel Weigh-in-Motion System
Researchers developed technology for a WIM system that can be easily built, can record vehicle weight across four lanes of traffic and does not need to use actual vehicles to calibrate. The system is much less expensive and easier to modify than a proprietary system.
Using Intelligent Transportation Systems Data to Improve Transit Performance and Management
Researchers analyzed the data collected by automatic vehicle location and automatic passenger counter systems on a Metro Transit bus route to understand and address its service reliability issues, developing a study methodology that can be applied to improve additional routes.
Investigation of Low-Temperature Cracking in Asphalt Pavements
In the cold climates of the northern United States, asphalt pavements are susceptible to low-temperature cracking. This study identified simple laboratory tests for predicting the fracture resistance of asphalt mixtures, procedures that were found to correspond to field performance.
Surveying Noxious Weeds in Roadway Rights-of-Way
Mn/DOT District 4 staff used a new sampling procedure to locate and measure infestations of noxious weeds and concluded that examining a greater number of much smaller areas, selected with regard to ecozone, was more accurate and would allow for better targeting of weed control resources.
Rural and Urban Safety Cultures: Human-Centered Interventions Toward Zero Deaths in Rural Minnesota
To help Mn/DOT shape safety interventions, rural and urban respondents answered survey questions about driving risks and behaviors. A small group then underwent driver testing in simulated urban and rural environments. Rural drivers were found to have lower perceptions of driving risk, and the rural environment appears to encourage unsafe speed choices and intersection crossing behavior, particularly among teen drivers.
Freeway Network Traffic Detection and Monitoring Incidents
Full Report: 2007-40
We propose methods to distinguish between moving cast shadows and moving foreground objects in video sequences. Shadow detection is an important part of any surveillance system as it makes object shape recovery possible, as well as improves accuracy of other statistics collection systems. As most such systems assume video frames without shadows, shadows must be dealt with beforehand. We propose a multi-level shadow identification scheme that is generally applicable without restrictions on the number of light sources, illumination conditions, surface orientations, and object sizes. In the first level, we use a background segmentation technique to identify foreground regions that include moving shadows. In the second step, pixel-based decisions are made by comparing the current frame with the background model to distinguish between shadows and actual foreground. In the third step, this result is improved using blob-level reasoning that works on geometric constraints of identified shadow and foreground blobs. Results on various sequences under different illumination conditions show the success of the proposed approach. Second, we propose methods for physical placement of cameras in a site so as to make the most of the number of cameras available.
Minnesota's Transportation Research Site Database
During a five-year project, researchers created and populated a database of the many roadway test sections created for research projects across Minnesota over the last several decades. This maximizes test section investments by putting original test data as well as more recent observations of test sites within the reach of city, county and state engineers.
Biological Control of Canada Thistle
Researchers investigated the effectiveness of the recently discovered biological control agent PST for the control of Canada thistle in roadside rights-of-way and prairie wetland restoration systems, and found that an integrated management system based on PST has a significant impact on the management of this weed.
Using Real-Time Road Condition Measurements for Automated Winter Road Maintenance
Researchers developed and tested a first-of-its-kind measurement system that, when mounted on snowplows, produces real-time measurements of the tire-road friction coefficient. These measurements are used to automatically adjust the application of deicing chemicals, which allows deicing materials to be used more efficiently and reduces environmental damage from chemical runoff.
Can Cone Penetration Testing Measure the Resilient Modulus of Soils?
Researchers evaluated the feasibility of using Cone Penetration Testing data to estimate resilient modulus in the field and to identify organic soils. Results show that while the statistical analysis model used by researchers was not sufficient to evaluate resilient modulus or organic soil content, this study provides groundwork for enhancing this model to further the use of CPT in the field.
Access to Destinations: Travel Time Estimation on Arterials
Full Report: 2007-35
The primary objective of this project was to identify and evaluate parametric models for making default estimates of travel times on arterial links. A review of the literature revealed several candidate models, including the Bureau of Public Roads (BPR) function, Spiess's conical volume delay function, the Singapore model, the Skabardonis-Dowling model, and the Highway Capacity Manual's model. A license plate method was applied to a sample of 50 arterial links located in the Twin Cities seven county metropolitan area, to obtain measurements of average travel time. Also obtained were the lengths of each link, measurements of traffic volume, and signal timing information. Default values for model parameters were obtained from the Twin Cities planning model's database. Using network default parameters, we found that the BPR and conical volume-delay models produced mean average percent errors (MAPE) of about 25%, while the Singapore and Skabardonis-Dowling models, using maximal site-specific information, produced MAPE values of around 6.5%. As site-specific information was replaced by default information the performance of the latter two models deteriorated, but even under conditions of minimal information the models produced MAPE values of around 20%. A cross-validation study of the Skabardonis-Dowling model showed essentially similar performance when predicting travel times on links not used to estimate default parameter values.
Implementation of Ground Penetrating Radar
Full Report: 2007-34
The objective of this project was to demonstrate the capabilities and limitations of ground penetrating radar (GPR) for use in local road applications. The effectiveness of a GPR survey is a function of site conditions, the equipment used, and experience of personnel interpreting the results. In addition, not all site conditions are appropriate for GPR applications. GPR is a nondestructive field test that can provide a continuous profile of existing road conditions. GPR utilizes high-speed data collection at speeds up to 50 mph, thus requiring less traffic control and resulting in greater safety. GPR has the potential to be used for a variety of pavement applications, including measuring the thickness of asphalt pavement, base and sub-grade; assisting in the analysis of rutting mechanisms; calculating and verifying material properties; locating subsurface objects; detecting stripping and/or layer separation; detecting subsurface moisture; and determining depth to near-surface bedrock and peat deposits. These applications are discussed in reference to 22 projects completed throughout the State of Minnesota. Three reports were produced. 1. A technical summary report provides an overview of the project. 2. A comprehensive review of GPR applications for use on local roads is also available. 3. The final report describes the results of the GPR surveys.
Intersection Decision Support: An Overview
Full Report: 2007-33
Minnesota joined with California, Virginia, and the FHWA in a pooled fund consortium (the Infrastructure Consortium) dedicated to improving intersection safety. The Minnesota team's objective is to develop effective strategies to mitigate high crash rates at rural intersections. Rural Intersection Decision Support (IDS) focuses on enhancing the driver's ability to successfully negotiate rural intersections. The system uses sensing and communication technology to identify safe gaps in traffic on a high-speed rural expressway and communicate this information to drivers waiting to enter the intersection from a minor intersecting road. The goal of this system is to improve safety without introducing traffic signals, which on high-speed rural roads often lead to an increase in rear-end crashes. The Rural IDS research program achieved four main research results: an analysis of rural expressway intersections, including development of a technique to identify those with higher-than-expected crash rates; development of a statistical model that can be used to estimate the benefits of deploying IDS at a specific rural intersection; design and implementation of a rural intersection surveillance and data acquisition system capable of quantifying the behavior of drivers; and a task analysis, design study, and simulator-based evaluation of Driver Infrastructure Interface (DII) concepts for communicating relevant information to stopped drivers.
Benefit-Cost Analysis for Intersection Decision Support
Full Report: 2007-32
The Intersection Decision Support (IDS) system is designed to assist drivers on stop-controlled low-volume rural roads choosing gaps when confronted with busy multiple lane divided-highways, without affecting traffic on the high-volume road. The hope is, that by providing better gap guidance, fewer crashes (and fatalities) will occur. This research develops a framework for analyzing such a new, and presently under-specified technology, and illustrates that framework by comparing that with more conventional engineering approaches, as well as a do-nothing base case. The results show that the IDS System may be an effective tool to reduce crash rates at various intersections. More research is needed to address reliability and stability issues, and in determining how cost-effective of a solution the IDS System is compared to other traditional alternatives.
A Simulator-based Evaluation of Smart Infrastructure Concepts for Intersection Decision Support at Rural Thru-STOP Intersections
Full Report: 2007-31
This report describes the human factors basis for an intersection decision support (IDS) system intended to improve the safety of rural intersections in Minnesota's Interregional Corridors (IRCs). The purpose of the human factors effort is to understand the task of rural intersection negotiation, identify high-risk user groups, describe the human factors that contribute to intersection accidents, and determine what conceptual types of information to present in the IDS display to improve driver performance and safety. Consistent with the original infrastructure consortium proposal, this report emphasizes gaps, older drivers, and rural thru-STOP intersections (Donath & Shankwitz, 2001). This is because older drivers have a high accident risk at rural thru-STOP intersections and problems with gap detection, perception, and acceptance are contributing factors. A task analysis of rural thru-STOP negotiation was used to define the informational requirements for an IDS system for assisting with gap detection, perception and judgment. An abstraction hierarchy defined the operator (driver) constraints relevant to an infrastructure-based IDS system. Four design concepts were constructed and tested in a driving simulator with older (55+) and younger (20-40) drivers in day and night driving conditions. Two designs resulted in the largest mean gap acceptance across groups when compared to baseline. The two design concepts also were most favored by the majority of participants.
Intersection Decision Support Surveillance System: Design, Performance and Initial Driver Behavior Quantization
Full Report: 2007-30
In rural Minnesota, approximately one-third of all crashes occur at intersections. Analysis of crash statistics and reports of crashes at rural expressway through-stop intersections shows that, for drivers who stop before entering the intersection, the majority of crashes involve an error in selecting a safe gap in traffic. The Intersection Decision Support system, developed at the University of Minnesota, is intended to reduce the number of driver errors by providing better information about oncoming traffic to drivers stopped at intersections. This report deals primarily with the surveillance technology which serves as the foundation upon which the IDS system will be built. Three components of the surveillance system are described in detail in the body of the report: 1) a Mainline Sensor subsystem; 2) a Minor Road Sensor subsystem; 3) a Median Sensor subsystem. These subsystems include radar units, laser-scanning sensors, and infrared cameras, integrated with a vehicle tracking and classification unit that estimates the states of all vehicles approaching the intersection. The design, installation, performance, and reliability of each of these three subsystems are documented in the report.
Evaluation of Minnesota's Operation NightCAP
Full Report: 2007-29
This project evaluated Minnesota Department of Public Safety's (Mn/DPS) Operation NightCAP (Concentrated Alcohol Patrol) Program. This overtime enforcement program uses saturation patrols to identify impaired drivers. The project consisted of 3 tasks: a crash data analysis, a driver survey and an officer survey. The crash analysis indicated that saturation patrols have a marginally statistically significant effect on the decrease in fatal and severe-injury alcohol-related crashes rates in Minnesota. The effect of a single saturation is small (~0.1%), indicating that many patrols would be needed to see significant decreases in alcohol-related crash rates. A survey of 5000 Minnesota drivers in 6 counties resulted in 838 completed surveys. Approximately 19% of Minnesota drivers are aware of the Program. Drivers' beliefs about impaired driving influenced their perception of alcohol-enforcement programs and their choices to drive after drinking. Fourteen Program Coordinators and 86 law enforcement officers from the Program also responded to a survey and shared their perceptions about the Program's effectiveness. Main conclusions drawn from the surveys were that saturation patrols are not highly visible to the public and the current Program advertising is not very effective in communities where it is active. Main recommendations are to improve patrol visibility and associated advertising.
Review of Georgia's Rural Intersection Crashes: Application of Methodology for Identifying Intersections for Intersection Decision Support (IDS)
Full Report: 2007-28
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 Georgia.
Review of Iowa's Rural Intersection Crashes: Application of Methodology for Identifying Intersections for Intersection Decision Support (IDS)
Full Report: 2007-27
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 Iowa.
Local Road Funding History in Minnesota
Full Report: 2007-26
Between 1993 and 2003 per capita city and county spending for streets and roads in Minnesota increased by about 0.9 percent per year after adjusting for inflation. Local expenditures for the construction of new roads and the expansion of existing road increased by 17 percent during that period. But, local operating spending on roads, which includes expenditures for road maintenance, fell by 3 percent. Per capita county and city receipts from state highway aid declined 5 percent during that 10-year period on an inflation adjusted basis. Although the ratio of local government spending to personal income fell by 0.5 percentage points between 1993 and 2004, the proportion of Minnesota personal income going for local streets and roads fell by less than 0.1 percentage points.
Measuring the Material Properties of Aggregate Base Containing Recycled Materials
Researchers performed both field and laboratory measurements of resilient modulus for three reconstructed roads that used recycled asphalt paving material in the pavement base, and also performed modulus, shear strength and deformation tests on reclaimed aggregate base and recycled asphalt mixed at various ratios. This established procedures and generated necessary inputs for Mn/DOT's pavement design manual.
Access to Destinations: Refining Methods for Calculating Non-Auto Travel Times
Full Report: 2007-24
The functioning of the system of land use and travel networks in a region can be encapsulated into measures of the ease of reaching destinations from various locations, often referred to as accessibility measures. Regardless of the form used to specify accessibility, all measures require as inputs travel times between the zones of a region. For most transportation planning purposes, these travel time calculations are limited to motorized modes (auto and public transit), since these modes carry the bulk of all urban travel. In this research study, attention is focused on developing methods for calculating travel times by non-auto modes, including walking, bicycling and public transit. Unique networks for each mode are developed, accounting for the presence of special facilities such as pedestrian or bicycle trails and on-street bike lanes. A statistical model is estimated to identify the influence of special bicycle facilities on travel speeds, using GPS data collected from bicyclists in a real-world setting. These methods are demonstrated with an application to a section of the Twin Cities metropolitan region encompassing parts of the cities of Minneapolis, St. Paul and Bloomington. The output of the application of these methods are a set of maps depicting travel sheds from various locations within the study area. The data are displayed for three points in time: 1995, 2000 and 2005. Changes to these travel sheds over time are demonstrated with maps that show the difference in travel time between each set of origins and destinations for each pair of years. The research concludes with some suggestions about the uses of the travel time data, such as the calculation of multimodal, multipurpose measures of accessibility.
Adaptation of the 2002 Guide for the Design of Minnestoa Low-Volume Portland Cement Concrete Pavements
Full Report: 2007-23
A new Mechanistic-Empirical Pavement Design Guide (MEPDG), also known as the 2002 Design Guide, was recently proposed in the United States. The development of such a procedure was conducted by the National Cooperative Highway Research Program (NCHRP) under sponsorship by the AASHTO. The Design Guide is a significant innovation in the way pavement design is performed. A comprehensive evaluation of the MEPDG performance predictions was conducted. It was found that the faulting model produced acceptable predictions, while the cracking model had to be adjusted. The cracking model was re-calibrated using the design and performance data for 65 pavement sections located in Minnesota, Iowa, Wisconsin, and Illinois. A prototype of the catalog of recommended design features for Minnesota low volume PCC pavements was developed using the MEPDG version 0.910. The catalog offers a variety of feasible design alternatives (PCC and base thickness, joint spacing and PCC slab width, edge support type, and dowel diameter) for a given combination of site conditions (traffic, location, and subgrade type). It is recognized, however, that version 0.910 is not the final version of the MEPDG. Therefore, the catalog should be updated after the MEPDG software is finalized.
Putting Research into Practice: Implementing a Fatigue Detail Classification Scheme for MnDOT's Steel Bridges
This project implements research that classifies steel bridges based on the frequency and severity of fracture and fatigue-sensitive details that are present in each bridge. The gross ranking of bridges with high, medium or low need for preventive maintenance or special inspection will be stored in Pontis, MnDOT's bridge management database, for use by bridge inspectors and those responsible for managing Minnesota's bridges.
Evaluating the Effectiveness of the Minnesota Speed Management Project
Final Report: 2007-21
The Minnesota Speed Management Program (MSMP), a cooperative project between the Minnesota Department of Transportation and the Minnesota Department of Public Safety, was developed within the framework of the Minnesota Comprehensive Highway Safety Plan. The overall goal was to reduce the number of fatal and life-changing crashes on Minnesota highways. The MSMP involved a speed limit adjustment-on 850 miles of Minnesota's 55 mph highways the speed limit was increased to 60 mph. It involved increased speed enforcement-by State Patrol, county sheriffs, and local law enforcement-on selected highways. There were four waves of Enhanced Enforcement (one of six weeks, three of eight weeks) each followed by four weeks of Regular Enforcement. The MSMP involved extensive public education, organized by the Office of Traffic Safety, with approximately 10,000 public service messages presented on the radio. Two evaluation efforts were conducted. The University of Minnesota compared travel speed data and crash data obtained during the MSMP with historical data. Throughout the MSMP, there were decreases in the number of drivers traveling at least 10 mph above the speed limits-decreases of -28.7% on 2-Lane/2-Way Highways; -28.7% on 4-Lane Divided Highways; -42.9% on Rural Freeways; and -11.2% mph on Urban Freeways. The University's evaluation also showed there were reductions in the numbers of fatal and life-changing crashes during the MSMP. MarketLine Research conducted the second evaluation, using telephone surveys, and found nine in ten drivers support the speed limit increase from 55 mph to 60 mph in both Metro and Greater Minnesota. The MSMP, in concert with other efforts that are part of the Minnesota Comprehensive Highway Safety Plan, resulted in reductions in the number of speeders on Minnesota Highways and reductions in the number of fatal and life-changing crashes-making Minnesota's roads safer.
North/West Passage ITS Integrated Corridor Strategic Plan
Final Report: 2007-20
The vision of the North/West Passage Corridor is to immediately influence ongoing standards development and utilize effective methods for sharing, coordinating, and integrating traveler information across state borders. While travel information reflects the initial destiny, maintenance and operations and planning and programming are long-term visions. The vision provides a framework to guide the states' future projects in the corridor. Conversely, a set of near-term goals and objectives are also identified in the plan and are based on the issues and needs currently faced in the corridor. Building upon the high-level architecture and assessment, a series of projects were then identified in the strategic plan. Projects were selected based on their ability to achieve the traveler information and maintenance operations goals identified earlier in the strategic plan. The projects are presented in a recommended sequence and contain details on approach, potential benefits, affected stakeholders, and estimated costs. With this strategic plan, the North/West Passage states have developed a set of recommended projects geared toward achieving their near-term goals. These projects may be folded into annual work plans or used to secure future funding for the corridor. The plan also establishes a process for future project development that will enhance deployment efforts in the corridor. Ultimately, this plan will help the North/West Passage achieve their vision to influence ongoing standards development and utilize effective methods for sharing, coordinating, and integrating traveler information across state borders.
Precast Concrete Pavement Panels on Minnesota Trunk Highway 62 - First Year Performance Report
Final Report: 2007-19
In June 2005, precast concrete pavement panels were installed during a trunk highway pavement rehabilitation project in Minneapolis, Minnesota. The panels were installed to evaluate the use of precast panels toward reducing construction time. Since it was the first precast concrete pavement panel project to be installed in Minnesota, it was deemed important to monitor the early and long-term performance of the system. This report describes the general condition of the precast pavement system after 1.5 years of service. The report also presents results from non-destructive testing conducted both immediately following construction and after one year of service. Finally, the report describes the condition of typical concrete pavement rehabilitation repairs conducted adjacent to the installed panels. A visual distress survey after 1.5 years of service revealed virtually no distress for both the precast panel sections and nearby conventional concrete pavement rehabilitation repairs. The ride quality of both the precast and conventional repair sections at 10 months of service was very smooth, with an International Roughness Index (IRI) value of approximately 50 inches per mile. The load transfer efficiencies of the precast panel joints were found to be over 90 percent after 1 year of service.
Performance of Ultra-Thin Bounded Wearing Course (UTBWC) Surface Treatment on US-169 Princeton, Minnesota
Final Report: 2007-18
The purpose of this report is to evaluate the performance of 1999 and 2000 ultra-thin bounded wearing course (UTBWC) surface treatment on US-169 in Princeton, Minnesota. The UTBWC consisted of gap graded course aggregate hot mix asphalt over a heavy asphalt emulsion layer and it was placed at an average thickness of inches. For comparison purposes, a control section was established to assess the performance of the overlay. This section continues to be maintained using standard sealing and patching techniques. The surface roughness and condition of these sections have been monitored on yearly basis. The overall performance of the UTBWC sections has been very good, while the control section is currently in need of major rehabilitation. The UTBWC appears to provide an economical choice for pavements in need of minor rehabilitation. In addition, UTBWC may prove beneficial as a preventive maintenance option. It should be considered for all sections with minor cracking and roughness distresses that do not stem from subgrade problems. Nationwide research has shown that UTBWC reduces deterioration caused by weathering, oxidation, traffic and provides good skid resistance, reduced rolling noise, reduction of hydroplaning, and back spray from roadway. UTBWC does not increase the structural capacity of the pavement, however, the use of UTBWC on new pavements as a wearing course could be considered.
MnROAD Cell 64 Pervious Concrete - First Year Performance Report
Final Report: 2007-17
This report evaluates the first year performance of the Pervious Concrete test cell #64 located in the parking lot on the south side of the MnROAD pole barn. Performance measures utilized for this report include examination of stress-strain response through loading from the 80 kip MnROAD truck and Falling Weight Deflectometer (FWD). The FWD deflection basins were compared to those obtained for normal concrete of similar thickness design. The second performance measure was the vibrating wire strain gauge sensor response. Elastic modulus values were computed from the sensor data. In addition, petrographic analyses of cores taken from the test pad and pavements were performed to determine the macroscopic and microscopic characteristics of pervious concrete pavement after the first year. Furthermore, a surface rating of the pavement was performed to corroborate petrographic and freeze-thaw data in order to ascertain the cause of any structural anomalies within the pervious concrete structure. Overall, the pervious concrete cell #64 is performing well after its first year. Normal sanding and salting operations do not appear to have impacted the pore structure within the pervious concrete to date. However, a more quantitative method of measuring flow through the cell and base materials is needed before a final conclusion can be made about the enduring ability of pervious concrete to pass water. Such a quantitative flow measurement method is currently under development. The structure of the pervious concrete cell #64 remains strong after a year of FWD/MnROAD truck loading and normal usage by vehicular movement over the driveway. Microcracking observed from petrographics does not appear to be worsening. Spalling and raveling conditions appear to have stabilized and are surficial in nature. This report concludes that pervious concrete is performing well in cell 64, and with continuous monitoring there will be greater confidence in more low volume applications.
A Synthesis of Research and Resources on Local Road and Bridge Funding for Local Public Works Officials
Final Report: 2007-16
Each year, literally thousands of books, articles, reports, policy studies, databases and analytical tools are published or prepared by practitioners, analysts, and academics all over the world on the subject of local road finance. The author/editor has reviewed hundreds of documents and other resources in an effort to identify those that have the most potential to directly assist local officials through better understanding of current and alternative funding policies, better awareness of existing analytical tools and other resources, and greater familiarity with available funding sources and procedures. Each resource identified contains the author or organization who prepared the resource document, along with a citation or other useful information to assist the user in gaining access to the information.
Commuter Bicyclist Behavior and Facility Disruption
Researchers tracked bicycle commuters' behavior using small Global Positioning System receivers enhanced by a wide-area augmentation system to better understand how infrastructure improvements and disruptions impact cyclists. Small GPS units offer an accurate and affordable method for tracking commuter behavior and will provide transportation planners with data to help prioritize infrastructure improvements.
Employment of the Traffic Management Lab for the Evaluation and Improvement of Stratified Metering Algorithm - Phase III
Full Report: 2007-13
The evaluation results (done in Phase II) demonstrated that the SZM strategy was generally beneficial. However, they also revealed that freeway performance degraded by reducing the ramp delays. Therefore, it is desired to improve the effectiveness of the current SZM control. There are two objectives in this study. One objective is to improve the control logic of current SZM strategy. This is accomplished through an estimation algorithm for the refined minimum release rate. The simulation results indicate that the improved SZM strategy is very effective in postponing and decreasing freeway congestion while resulting in smoother freeway traffic flow compared to the SZM strategy. The second objective of this project is to improve the current queue size estimation. Depending on the counting error of queue and passage detectors, freeway ramps are classified into three different categories, and different methods are applied respectively for improved queue size estimation. The surveillance video data were recorded and used to verify the improvement of the proposed methods. The results indicate that the proposed methods can greatly improve the accuracy of queue size estimation compared with the current methodology. Also, the proposed method was evaluated by the micro-simulation. The simulation results indicate the performance of freeway mainline is significantly improved. And the total system performance is better than the original SZM control.
Repair or Replace Concrete Bridge Decks?
Methods to Select the Lowest Cost Alternative Researchers performed an economic analysis to identify the most cost-effective maintenance strategies for a large group of aging concrete bridge decks. Based on current prices, researchers determined that repair is preferable to redecking if repair can elevate a deteriorated deck to an acceptable condition. Researchers also developed least-cost repair/replacement strategies for all of the decks in the group.
Demonstration of Ash Utilization in Low Volume Roads
Coal fly ash was used to stabilize reclaimed pavement materials in two Minnesota construction projects to demonstrate the viability of this practice. The ash-treated materials displayed improved stiffness, and analysis of leached moisture did not reveal unsafe trace element levels.
Pavement Design Using Unsaturated Soil Technology
A new method of using the principles of unsaturated soil mechanics during pavement design was developed. This will allow pavement engineers to better take into account field conditions and seasonal variations in moisture content. The new models developed in this study allow pavement designers to estimate the stiffness and strength of any soil encountered in the field.
Field Validation of Intelligent Compaction
Researchers evaluated intelligent compaction monitoring technology used in earthwork construction for quality control and assurance. They found that while IC technology is a feasible alternative for quality control and potentially quality acceptance, some challenges remain in validating IC rollers to accurately interpret their measurements.
Implementing the International Roughness Index for Concrete Pavement Evaluation
Mn/DOT was trying to improve its method for awarding bonuses to contractors for especially smooth concrete pavement. Investigators compared the old method for measuring smoothness to the new International Roughness Index standard, looking at how each pavement analysis method depicts various surface imperfections and evaluating the different options for implementing IRI incentives.
Improving the Strength and Stability of Prestressed Concrete Through-Girder Pedestrian Bridges
Because of a growing concern about the overall safety of pedestrian bridges, investigators used laboratory studies and computer simulation to gauge their ductility, strength and stability as compared with AASHTO specifications. Results showed that several modifications to AASHTO bridge specifications will make future pedestrian bridges stronger and more resistant to collapse.
Increasing the Recycling of Manufactured Shingle Scrap in Minnesota: A Market Development Project
Final Report: 2007-07
This Mn/DOT Shingles Recycling Project was initiated to help accelerate the implementation of the use of manufacturers' shingle scrap into hot mix asphalt (HMA) in Minnesota. The intent was to help increase demand for manufacturers' recycled asphalt shingles in Minnesota through targeted outreach and technology transfer tools by addressing the information needs of private contractors and local agencies. Therefore, A Guide to the Use of Roofing Shingles in Road Construction was produced as part of a larger outreach and education campaign. Through interviews with HMA producers and other private companies, it was concluded that there was already very good acceptance of shingle recycling technology and that lack of adequate demand was not the key barrier to further market development. Rather, the lack of readily available supply of manufacturers' shingle scrap was determined to be the key barrier to further growth in recycling of this material. Most of the manufacturers' shingle scrap was already committed to a few recyclers and therefore did not allow new business entries into the marketplace. Recommendations for continued Mn/DOT market development support activities include additional research and specification development. The future promise of recycling tear-off shingle scrap may help address the limited supply of manufacturers' scrap.
MnROAD Lessons Learned
Final Report: 2007-06
The Minnesota Department of Transportation (MnDOT) began construction on the Minnesota Road Research Project (MnROAD) in 1991 and opened the full-scale pavement research facility to live traffic in 1994. Since the time of its construction, MnROAD, the first major test track since the AASHO Road Test of the 1950s and 1960s, has learned a number of lessons on behalf of the greater pavement community. As part of completing the first phase of MnROAD (its first ten years of operation), researchers at the University of Minnesota reviewed the many products of MnROAD's first phase. The Lessons Learned project involved over fifty interviews, three hundred published and unpublished reports, papers, and briefs, and an online survey of pavement professionals. This report presents an overview of MnROAD products of interest at the local, state, and national levels. Furthermore, the report provides extensive references for these products in hopes of increasing awareness of MnROAD's under-publicized contributions to pavement engineering.
Resilient Modulus and Strength of Base Course With Recycled Bituminus Material
Final Report: 2007-05
The objective of the research was to determine the strength and deformation characteristics of base material produced from recycled asphalt pavement (RAP) and aggregate. Various samples with different ratios of RAP and aggregate base were mixed (% RAP/aggregate): 0/100, 25/75, 50/50, 75/25. Laboratory compaction testing and field monitoring indicated that gyratory compacted specimens were closer to the densities measured in the field. Resilient modulus (MR) tests were generally conducted following the National Cooperative Highway Research Program 1-28A test protocol. MR increased with increase of confining pressure, but MR showed little change with deviator stress. The specimens with 65% optimum moisture contents were stiffer than the specimens with 100% optimum moisture contents at all confining pressures. Cyclic triaxial tests were conducted at two deviator stresses, 35% and 50% of the estimated peak stress, to evaluate recoverable and permanent deformation behavior from initial loading to 5000 cycles. The specimens with RAP exhibited at least two times greater permanent deformation than the 100% aggregate material. As %RAP increased, more permanent deformation occurred. In summary, the base material produced with various %RAP content performed at a similar level to 100% aggregate in terms of MR and strength when properly compacted.
The Safety of Pedestrian and Bicycle Travel in Minnesota: Inventory, Analysis and Prospectus
Researchers scanned the available sources of accident data involving bicycles and pedestrians for trends such as correlations between accidents and neighborhood attributes. They examined current accident data collection and made recommendations to increase the quantity, quality and use of bicycle and pedestrian crash data.
Measuring the Safety Effects of Signal Installation and Left-Turn Phasing Schemes
Researchers analyzed before-and-after crash data, and used statistical analysis and computer modeling to measure the safety effectiveness of Mn/DOT's practices for signal installations and left-turn signal phasing schemes at highway intersections. The research findings were roughly consistent with Mn/DOT's guidance and practice in these areas; analysis should be repeated in several years when more after-treatment data are available.
Factors Affecting Commute Times in the 1990s
The average length of time it took Minnesota workers to commute to work increased about 2.5 minutes during the 1990s, a larger-than-normal increase. Unidentified factors other than urban sprawl and traffic congestion were thought to be creating a significant shift in commuter behavior. A detailed statistical analysis showed little correlation between economic factors and commute times, and that some of the increase was due to a change in methodology in the 2000 census.
Use of Ground Penetrating Radar to Evaluate Minnesota Roads
Final Report: 2008-01
The Minnesota Local Road Research Board (LRRB) funded a project to evaluate the usefulness of ground-penetrating radar (GPR) in evaluating Minnesota roads. A literature search was first performed to review the applications of ground-penetrating radar (GPR) to highway applications. These applications include calculating layer thickness, estimating asphalt density, determining aggregate base moisture content, identifying stripping within asphalt layers, detecting air voids and vertical cracks, identifying subsurface anomalies, and analyzing rutting mechanisms. The relative accuracy of using GPR as opposed to traditional field tests was assessed. A simple laboratory calibration was performed to estimate the thickness of a concrete slab to within 10%. Finally, a sensitivity study was performed to determine the dependence of various output parameters (minimum layer thickness, maximum depth of penetration, horizontal resolution, reflection coefficients, layer thickness, and air void thickness) on input parameters (antenna frequency and dielectric constant). GPR was successful in identifying total asphalt thickness on CSAH 61 in Pine County, and moderately successful in determining base thickness and identifying the underlying, original concrete roadway in select locations. The surveys were not successful in differentiating asphalt course thicknesses. The surveys also identified potential regions of stripping. GPR was not successful in locating near-surface bedrock or peat deposits on CSAH 48 in St. Louis County, because of the presence of a geo-textile membrane.