Search Content

This report summarizes an evaluation of the first year of the Cambridge Telework Center, where Minnesota Department of Transportation employee volunteers work one or two days a week instead of commuting to Twin Cities sites. Researchers surveyed participants and their supervisors at the beginning of their involvement, six months later, and a final survey a year later. The surveys asked questions about commuting time and distance, expectations about and experiences with telework, job satisfaction and other work attitudes, job performance, day-to-day operations at Cambridge, and other issues. The Telework Center reduces commuting time and distance by a per day average of 32 miles and 74 minutes. In the first survey, participants and supervisors expected to see improvements in a wide variety of areas, including quality and quantity of work, job satisfaction, and reduced stress. One year later, the two groups reported that most of these expectations were met, and they rated their telework experience as positive. However, according to direct measurements, teleworker job satisfaction and commitment to the organization remained unchanged from the program's start to one year later. The same proved true with job performance.

This report highlights an investigation into concrete pavement performance problems caused by transverse joint misalignment on a segment of westbound Interstate 94 near Fergus Falls, Minnesota. In 1986, heavy rain during construction resulted in transverse joint locations based on estimated sawing guide marks. The results of dowel bar alignment, faulting, and load transfer efficiency measurements all demonstrate that misaligned transverse joints in relationship to the dowel bar assemblies contributed to early faulting that a minimum dowel bar embedment length of 64 mm (2.5 in.) is needed to prevent significant faulting and maintain reasonable load transfer efficiency across a joint. However, construction alignment tolerances and long-term concrete stress reduction near the dowels warrant the use of embedment lengths longer than 64 mm (2.5 in.). Since several of the joints investigated can be considered undoweled, accelerated faulting of these joints can be expected.

Sleep deprivation and sleep disorder continues to cause problems on the road. Reducing the number of accidents related to driver fatigue would save the society a significant amount of money and personal suffering. Monitoring the driver's symptoms can help determine driver fatigue early enough to prevent accidents due to lack of awareness. This report describes advances towards a non-intrusive approach for real-time detection of driver fatigue. It uses a video camera that points directly toward the driver's face and monitors the driver's eye to detect micro-sleeps, or short periods of sleep of about three-to-four seconds.

This report focuses on the first extensive forensic excavation of a paved test cell at the Minnesota Road Research Project (Mn/ROAD). A trench was dug in Cell 28 of the Low Volume Loop at Mn/ROAD to investigate a localized failure of the roadway. This report documents the trenching process and serves as a historical record of the in situ conditions of Cell 28 in the early summer of 1997. Data collected during this forensic excavation has contributed to the conclusion that mechanistic pavement design methods should include a maximum allowable stress criteria for aggregate base and subgrade. In addition, minimum hot-mix asphalt pavement thicknesses are required to prevent failures of aggregate base and subgrade. The tests performed during the investigation, as well as the analysis of available data, are discussed. The conclusions of the forensic research team as to the historical performance and subsequent deterioration of Cell 28 also are included.

In this project, researchers examined the current practices that local agencies use and evaluated the thickness design procedures by comparing predicted lives for the current designs with those obtained from the mechanistic-empirical design procedure ROADENT. Researchers determined current practices by sending a questionnaire to all cities and counties and visiting two counties and one city. In general, the questionnaire responses show that cities and counties use a variety of practices for the design, construction, and management of low volume pavements in Minnesota. Relative to the current designs, ROADENT predictions of fatigue behavior require a thicker design for medium and high-traffic roads than the Soil Factor design, and a thicker design for high-traffic roads than the R-Value procedure. The required thicknesses based on development of rut depth are not consistent with the current designs. To develop consistent procedures for the design, construction, and management of low volume roads in Minnesota, the report recommends converting the differences in performance predictions to thicknesses through the use of existing procedures and the mechanistic-empirical procedure; developing a best practices manual; and implementing the design procedure and manual.

Digital phone service, also known as Personal Communication Systems (PCS), is becoming the preferred choice in wireless phone systems. PCS requires a communications transmittal network, which involves the placement of antennae about one mile apart. This report provides information about community reaction in other states to placing a wireless infrastructure in the right-of-way. It provides a general summary of the industry, a general summary of community reaction to wireless infrastructure placed in rights-of-way, and a summary of issues and topics related to community reaction to wireless infrastructure. The report includes a three-part bibliography that includes essential reading on the topic, items specific to the economic aspects, collocation, and aesthetics of wireless infrastructure, and other selected items that provide background information.

The Minnesota Department of Transportation (Mn/DOT) has concluded that at certain high speed locations, providing additional information to the motorist describing the operation of the traffic signal can assist the driver in making safer and more efficient driving decisions. The additional information includes a visual indication to get the driver's attention and a specific notice that the driver must prepare to stop. The Advance Warning Flasher (AWF) is a device which Mn/DOT uses to convey this information to the driver. The Mn/DOT A WF system consists of a flasher and a sign located on main street approaches to a high speed signalized intersection. The AWF is connected to the traffic signal in such a way that when the main street green is about to change to yellow, the flasher is turned on to warn the approaching drivers of the impending change. Basically, the purpose of an optimally designed combination of traffic signal and AWF system is twofold: 1) to inform the driver in advance of a required driver decision (prepare to stop) and 2) to minimize the number of drivers that will be required to make that decision. Over time, questions have arisen regarding the use and application of AWF devices. The purpose of this study was to examine the effectiveness of the current AWF operation and, where possible, to make recommendations to improve it. The study concluded that the use of AWF devices can be effective at reducing right angle and rear end accidents under certain situations but that the device does not automatically increase the safety of all intersections. Accordingly the device should be considered as a traffic engineering tool to be used to correct situations of special need. Further, this study developed a scheme to optimize AWF operation. The proposed approach will theoretically produce an optimized A WF location/operations scheme but must be field validated as part of a suitable test study.

The life of the various types of cutting edges for use on Motor Graders and Snowplows varies with the type of steel and its treatment by the manufacturer. This is an evaluation of the wear characteristics of five types of cutting edges, both Motor Patrol and Snowplow, used in the maintenance of gravel roads. Comparing the two sets of data (gravel and snow) excluding the Carbide edges, the Carbon is best on snowplows and second best but only slightly lower in durability than flame hardened on gravel blading. Gravel blading is about three times more severe than snowplowing on cutting edges other than Carbide Insert.

This report presents results of a series of nondestructive tests to estimate the strength of concrete in a twenty-year-old prestressed bridge girder removed from an interstate overpass. Nondestructive test results were compared with compressive strength tests of cores. In addition, chloride ion concentration of the concrete was analyzed to determine whether corrosion of the bridge reinforcing steel may have occurred. Nondestructive tests included rebound hammer, pulse velocity, Windsor probe, and break-off tests. Included is a review of commonly encountered strength correlations for each of the tests. Of the nondestructive tests, the rebound hammer and pulse velocity tests predicted concrete strength reasonably well with existing correlations. With one major exception, results from chloride ion tests indicated that sections of the bridge with greater exposure to deicing salts had a greater amount of chloride penetration. The exception was a facia girder exposed to incoming traffic. Rain may have had a beneficial effect by washing salt residue from the facia girder. Chloride ion penetration at the leveI of the reinforcing steel for the bridge girders tested was not found to be great enough to expect corrosion.

Prestressed concrete has been used as a bridge construction method in the United States since 1949. Presently, there are thousands of pretensioned prestressed concrete bridges in service in North America. Each year, approximately 200 girders are damaged as a result of impact damage (primarily overheight vehicles striking a bridge from below). This report describes the results of a four girder test series used to evaluate impact damage and effectiveness of repairs. The girders used for the study were fabricated in 1967 and placed into service. The girders were removed from service in 1984 as a result of a road realignment project. The objectives of the research project were to: 1) determine the effective prestress in the strands after 20 years; 2) determine the influence of impact damage on girder performance; 3) evaluate the performance of two impact damage repair schemes under static, fatigue and ultimate loadings; and 4) develop a model to estimate the strand stress ranges in damaged girders.