Research Reports

Many cities in the United States are installing roundabouts instead of traditional intersections, due to evidence that roundabouts dramatically reduce fatal and severe injury crashes compared to traditional signalized intersections. However, the impact on pedestrian safety is not clear. This project was developed to investigate pedestrian accessibility in Minnesota urban roundabouts, addressing complaints from pedestrians regarding difficulties in crossing and safety. The methodology followed in this ongoing research is typical of other observational studies. A sufficiently large number of observations on the interactions between pedestrians or bicycles (peds/bikes) and vehicles at two modern urban roundabouts in the Twin Cities of Minneapolis and St. Paul in Minnesota were collected and reduced. These observations have supported a two phased analysis. Phase 1 involved the extraction of general information describing the crossing event, such as who yielded, the location of the crossing, or the number of subjects involved. Phase 2 looked deeper into these factors by considering the conditions inside the roundabout before the vehicle proceeds to the crossing and meets with the ped/bike. The results presented, although containing no surprises, do highlight and categorize the existence of friction between pedestrians and drivers at roundabout crossings. Also the identification of factors affecting driver yield behavior and pedestrian wait time do offer good background for modeling such interactions.

Culvert pipe material selection has traditionally been a relatively simple task involving metal or concrete pipe. In recent years, the addition of coated metal and plastic pipe has led the federal government to implement a rule requiring the consideration of alternative pipe materials. The current MnDOT Drainage Manual provides limited guidance on the selection of pipe material. The manual is lacking detailed information on the influence of environmental conditions on pipe durability in Minnesota. It is necessary to provide updated, accurate information on pipe material and durability for factors directly related to Minnesota. To reach this goal, the availability and suitability of existing data, as well as the practices associated with predicting pipe life spans must be evaluated. This report is the result of the initial feasibility study for a larger project(s) to update the MnDOT Drainage Manual. The goal for this report is to identify knowledge gaps, produce a research plan that will guide future research, and draw any pipe materials conclusions possible using the data available.

Objective was to develop a work zone alert system to inform speeding drivers of the upcoming work zone. Furthe development is needed to ensure that the final product is crash proff and that it cna be produced efficiently.

The construction manager-at-risk (CMR) project delivery method, also termed construction manager/general contractor (CM/GC) project delivery in several states' enabling legislation, is an integrated team approach to the planning, design, and construction of a project to control schedule and budget and assure quality for the project owner. The team consists of the owner, the designer, which might be an in-house engineer, and the at-risk construction manager. Working toward a process to use the CM/GC project delivery method, the Minnesota Department of Transportation (MnDOT) identified industry stakeholders to engage and address concerns and work through ideas about CM/GC. The researchers reviewed the related literature, analyzed the content of 30 Request for Proposal/Request for Qualifications (RFP/RFQ) solicitation documents, and collected/compiled responses to a questionnaire (structured to answer MnDOT questions) that was sent to agencies in states that have used CM/GC. Survey questions and responses, as well as the targeted literature review and RFP/RFQ content analysis, are covered in the standalone white papers that were developed and included in this report to present the results of this investigation. The first five topics identified, presented to the stakeholder group, and, then, developed into white papers were as follows: CM/GC Project Selection, CM/GC Selection Process, CM/GC Selection Requirements, Subcontractors, and Cost Negotiations. Five additional topics were identified, developed into standalone white papers, and also included at the end of this report as follows: Including Cost in the CM/GC Selection Process, Design Contract Modifications, Owner Process to Validate Cost, Role of Independent Cost Estimator (ICE), and Contractor Bid Process.

The new I-35W Bridge was instrumented incorporating "smart bridge technology" by Figg Engineering Group in conjunction with Flatiron-Manson. The purpose of the instrumentation was to monitor the structure during service, and to use this information to investigate the design and performance of the bridge. Instrumentation included static sensors (vibrating wire strain gages, resistive strain gages and thermistors in the foundation, bridge piers, and superstructure, as well as fiber optic sensors and string potentiometers in the superstructure) and dynamic sensors (accelerometers in the superstructure). Finite element models were constructed, taking into account measured material properties, to further explore the behavior of the bridge. The bridge was tested using static and dynamic truck load tests, which were used, along with continually collected ambient data under changing environmental conditions, to validate the finite element models. These models were applied to gain a better understanding of the structural behavior, and to evaluate the design assumptions presented in the Load Rating Manual for the structure. This report documents the bridge instrumentation scheme, the material testing, finite element model construction methodology, the methodology and results of the truck tests, validation of the models with respect to gravity loads and thermal effects, measured and modeled dynamic modal characteristics of the structure, and documentation of the investigated assumptions from the Load Rating Manual. It was found that the models accurately recreated the response from the instrumented bridge, and that the bridge had behaved as expected during the monitoring period.

The work detailed in this report represents a continuation of the research performed in phase one of this national pooled fund study. A number of significant contributions were made in phase two of this comprehensive research effort. Two fracture testing methods are proposed and specifications are developed for selecting mixtures based on fracture energy criteria. A draft SCB specification, that received approval by the ETG and has been taken to AASHTO committee of materials, is included in the report. In addition, alternative methods are proposed to obtain mixture creep compliance needed to calculate thermal stresses. Dilatometric measurements performed on asphalt mixtures are used to more accurately predict thermal stresses, and physical hardening effects are evaluated and an improved model is proposed to take these effects into account. In addition, two methods for obtaining asphalt binder fracture properties are summarized and discussed. A new thermal cracking model, called "ILLI-TC," is developed and validated. This model represents a significant step forward in accurately quantifying the cracking mechanism in pavements, compared to the existing TCMODEL. A comprehensive evaluation of the cyclic behavior of asphalt mixtures is presented, that may hold the key to developing cracking resistant mixtures under multiple cycles of temperature.

A fully interactive PC-based STISIM driving simulator was used to test the effectiveness of Intelligent Lane Control Signals (ILCS). These ILCSs presented (1) 45-mph speed limit messages; (2) 35-mph speed limit messages; (3) a yellow lane closure warning; (4) one of three merge messages that used a diagonal arrow, or words, or dynamic chevrons to indicate that drivers should move from the center lane; (5) a red lane closure warning. Analysis of lane position data showed that the diagonal arrow merge sign was the most effective. Analysis of driving speed data indicated that the speed limit signs were effective.

This report presents an evaluation of wastewaters derived from concrete placement and maintenance and the preparation of best management practices (BMPs). Investigation and documentation of existing practices was done to ensure application to real situations and enhancement of constructability for all BMPs. Laboratory analysis of test specimens was done to provide characterization of factors that are likely to positively or negatively influence concrete wastewater composition. Evaluation of sedimentation and filtration through and absorption by sand and geotextile materials provides a simulation of the known control techniques. Development of a constituent occurrence and control model with a strong statistical base achieved through experimental replication supports development of BMPs that are both environmentally protective and constructible.

This research evaluated the ice melt capacity and field performance factors of deicers and deicer blends and then developed a temperature-based cost model for comparing the relative field performance of the evaluated deicers and deicer blends. Both solid and liquid deicers were evaluated for both deicing and anti-icing methods.

Highway funding in the United States has traditionally been done through user fees, most notably motor vehicle fuel taxes. However, there are growing concerns among some policymakers that fuel taxes are no longer adequate, sustainable, efficient, or equitable. Entities in the United States and abroad have conducted pilot projects or implemented mileage-based fees, including several specifically designed for heavy trucks. There are two major concerns related to truck travel: (1) heavy trucks consume a great deal of roadway capacity due to their size, operating characteristics, and annual miles traveled; and (2) roadway wear and tear caused by the combination of truck mileage and heavy loads is significant and disproportionate to the number of trucks on the road. The concept of mileage-based user fees has seen increasing support from a number of groups in recent years; however, it faces opposition from many in the general public and from the trucking industry. This paper is part of a larger effort exploring the benefits to the freight industry of mileage-based user fees, while highlighting industry concerns over its implementation.