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This study examined the physical characteristics of combustion aerosols found on Minnesota highways. It emphasized the characterization of nanoparticles (less than 50 nm) with the goal of providing real-world data for the development of engine laboratory test methods. On-road particulate matter emissions ranged between 10[to the 4th] to 10[to the 6th] particles/cm[to the 3rd] with the majority of the particles by number being less than 50 nm in diameter. High-speed traffic produced high nanoparticle number concentrations and diesel traffic further increased number concentrations. At high vehicular speeds, particulate matter emissions increase because of higher engine load and fuel consumption. Measurements made at speeds less than 20 mph showed lower number but higher volume concentrations and larger particles. Measurements made 10-30 m from the highway in residential areas approached on-road concentrations with similar size distributions and high concentrations of nanoparticles. Lower concentrations and larger particles were observed in residential areas 500 to 700 m from the highway. Fuel specific and particle/mi. emission rates were estimated from data collected on two different days. The particle/mi. emissions were about an order of magnitude greater than published figures but mass emission rates compared well with published values. However, colder temperatures, different dilution and sampling conditions and different instrumentation could explain the authors' increased estimates.

This project introduced the use of micro surfacing as a pavement preventive maintenance surface treatment and tested different methods of using micro surfacing to correct or prevent defects in existing pavements. Micro surfacing mixtures include polymer-modified emulsified asphalt cement, a well-graded 100% crushed mineral aggregate, and mineral filler, such as portland cement or hydrated lime, with water and control additives added to control the speed of breaking and workability. Micro surfacing remains semi-liquid during mixing and placing phases and then cures chemically for a very durable asphalt surface treatment. Application and testing revealed that the fast-moving micro surfacing process minimizes the amount of down time for traffic; does an excellent job of reestablishing cross sections; fills ruts; improves ride quality; increases friction numbers; and provides an excellent background for pavement markings. It does not seal reflective cracks, has generated some concerns about increased traffic noise, and does not work favorably for smoothing humps in pavement. Overall, project selection played a key factor in the overall success of micro surfacing. A very thin surface treatment, microsurfacing cannot be expected to fix structural problems in existing pavements. One should avoid using micro surfacing on roadways that are still rutting and repair potholes before placement of micro surfacing.

This research project resulted in a new, accurate way to assess fatigue cracking on Bridge 9340 on I-35, which crosses the Mississippi River near downtown Minneapolis. The research involved installation on both the main trusses and the floor truss to measure the live-load stress ranges. Researchers monitored the strain gages while trucks with known axle weights crossed the bridge under normal traffic. Researchers then developed two- and three-dimensional finite-element models of the bridge, and used the models to calculate the stress ranges throughout the deck truss. The bridge's deck truss has not experienced fatigue cracking, but it has many poor fatigue details on the main truss and floor truss system. The research helped determine that the fatigue cracking of the deck truss is not likely, which means that the bridge should not have any problems with fatigue cracking in the foreseeable future. As a result, the Minnesota Department of Transportation (Mn/DOT) does not need to prematurely replace this bridge because of fatigue cracking, avoiding the high costs associated with such a large project. The research also has implications for other bridges. The project verified that the use of strain gages at key locations combined with detailed analysis help predict the bridge's behavior. In addition, the instrumentation plan can be used in other similar bridges.

A section of Trunk Highway 23 near Mora, Minnesota, underwent concrete rehabilitation in 1998, which included the installation of retrofit dowel bars over a portion of the project. The Minnesota Department of Transportation (Mn/DOT) established several different test sections to evaluate the performance of different dowel bar configurations, group materials, and dowel bar lengths. During dowel bar installation, researchers monitored and evaluated construction procedures. They also conducted pavement testing before and after installation of the retrofit dowel bars to determine any immediate improvements to the joint performance. As expected, early age testing has shown improvements in joint load transfer efficiency after installation of the retrofit dowels. Testing also revealed that the rapid-setting mortar performed better than Mn/DOT's standard 3U18 patching mix. After only two years, there has been no noticeable differences in ride quality or faulting at the joints between retrofit and nonretrofit joints. Testing of pavements and joint performance will continue on a yearly basis to determine the long-term performance of the retrofit dowels.

This report describes a Bayesian method for estimating accident rates at individual sites, which takes into account the fact that the total traffic count usually used to measure exposure is generally not known with certainty. The first step involves deriving an approximation for the probability of distribution of total traffic conditioned on a short count sample. This approximation is then used to derive a Bayes estimator of a site's accident rate, conditioned on an accident count, a short count sample, and the total traffic approximation. The method then uses Gibbs sampling to compute accident rate estimates. Tests based on actual accident and traffic data revealed that accident rate estimates based on a two-week traffic sample area are almost as accurate as estimates based on full traffic counting, but that uncertainty in the estimated accident rates increase by 20 to 50% when using a two-day count sample.

This report presents the results of a research project to investigate the design and performance of thin and ultra-thin whitetopping. To learn more about whitetopping, the Minnesota Department of Transportation (Mn/DOT) constructed a whitetopping project consisting of six test sections on I-94 at a research facility and three test sections at intersections on US-169 at Elk River. This report includes a brief description of Mn/DOT history with whitetopping and a detailed description of the construction of the heavily instrumented whitetopping test sections on I-94 and US-169. All concrete mixes contained either polypropylene or polyolefin fibers. The compressive strength, flexural strength, Poisson's ratio, and elastic modulus were measured for these mixes, and the results are provided.

The Minnesota Department of Transportation's (Mn/DOT's) recent implementation of a 0.40 maximum water-to-cementitious ratio specification for concrete pavements has raised some concerns regarding the availability of bleed water at the pavement surface and the moisture retained in the concrete for strength development with current curing practices. A study was initiated in the spring of 1998 to evaluate Mn/DOT's concrete pavement curing requirements. First, an assessment of the effectiveness of various compounds frequently used on state funded projects was performed and the test methods used to evaluate these compounds were examined. Changes were made to Mn/DOT's curing specifications based on the finding of the first portion of this study and implemented during the 1999 construction season. Methods used by contractors to apply curing compounds were also reviewed to insure that a uniform coat of acceptable thickness is applied and recommendations were made for improving these methods. This paper summarizes the findings of this study and the resulting changes that were made to Mn/DOT concrete pavement curing specifications. Recommendations for further improvements are also provided.

This field manual provides guidelines for preventive asphalt pavement maintenance techniques for a variety of distresses and conditions. It covers: 1. crack treatments (clean and seal, rout and seal, full-depth crack repair); 2. surface treatments (fog seal, seal coat, thin hot-mix overlays); and 3. pothole patching and repair (cold-mix asphalt, spray injection patching, hot-mix asphalt, slurry or microsurfacing material).

For the Aesthetic Initiative Measurement System (AIMS) project, researchers developed and tested the instruments and protocols that the Minnesota Department of Transportation uses to understand and document how travelers perceive the attractiveness of Minnesota's transportation corridors. In summer 1999, researchers collected quantitative and qualitative data for three cities: Rochester, Twin Cities, and Duluth, Minnesota. Four key topics produced highly noticeable aesthetic effects to the travelers: maintenance, planting design, structural design, and vistas from the highway. The consistency of AIMS results with previous studies of other landscaped settings suggested that AIMS results are valid and could be replicated in other urban highway routes and with rural highways.

This report summarizes the results from the technical support and testing of the freeway traffic simulation software developed at the University of Minnesota. The University's Civil Engineering Department developed and implemented an experimental course that addressed fundamental theories in traffic flow modeling and simulation. They also incorporated a set of an online help manual into simulation software. Software testing was conducted through two sets of case studies involving the high-occupancy vehicle (HOV) lane and ramp metering simulation modules. The HOV lane case study used a 10-mile section of the westbound I-94 freeway with an additional lane and evaluated the performance of alternative HOV lane strategies with different sets of demand and HOV proportions. For the same amount of total demand without assuming induced trips, the higher the HOV proportion, the smaller the mainline delay. The ramp metering case study compared the performance of the current Minnesota Department of Transportation metering policy with that of a no-metering option for a 16-mile section of the northbound 169 freeway with 20% higher demand than the current level. The metering case study showed that the total system delay, including both mainline ramps, was significantly reduced when the ramps were controlled compared to a no-metering case for a given set of demand. The case studies indicate that the simulation software can be applicable in evaluating alternative design and operational strategies for a given set of demands.