bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization Tests for Mineral Fillers Related to Performance of Asphalt Paving Mixtures
Authors: Kandhal Prithvi S. , Lynn Cynthia Y. , Parker Frazier
Published: April 2007

Various studies have shown that the properties of mineral filler, especially the material passing through a 0.075-mm (No. 200) sieve (generally called P200 material), have a significant effect on the performance of asphalt paving mixtures in terms of permanent deformation, fatigue cracking, and moisture susceptibility. However, researchers have employed different characterization tests for evaluating the P200 materials. This study was undertaken to determine which P200 characterization tests are most related to the performance of asphalt paving mixtures. Six P200 materials representing a wide range of mineralogical composition and particle size were used. These P200 materials were characterized by six tests including Rigden voids, particle size analysis, and methylene blue test. Mixes were prepared with two fines to asphalt ratios (0.8 and 1.5) by weight. Mix validation tests included the Superpave shear test for evaluating permanent deformation and fatigue cracking, and the Hamburg wheel tracking test and AASHTO T283 for evaluating moisture susceptibility of the 12 mixtures containing different P200 materials and fines to asphalt ratios. The particle sizes in microns corresponding to 60 and 10 percent passing and the methylene blue test were determined to be related to the performance of asphalt paving mixtures.
Evaluation of Superpave Gyratory Compaction of Hot Mix Asphalt
Authors: Mallick Rajib B. , Buchanan Shane , Brown E. Ray , Huner Mike
Published: April 2007

The effect of restricted zone on volumetric properties of mixes consisting of all crushed, and all crushed and partially uncrushed, materials was evaluated. For a given aggregate blend, gradations below or above the restricted zone provided higher voids in mineral aggregate (VMA) than mixes through the restricted zone. Mixes with crushed aggregate provided higher VMA than mixes with partially crushed aggregate. It is recommended that further work be conducted to evaluate the effect of different types and shapes of aggregates on the volumetric properties of specimens compacted with the Superpave gyratory compactor. According to the current Superpave mix design system, the bulk specific gravity of a compacted specimen at any gyration is back calculated from the bulk specific gravity determined at Nmaximum and a correction factor determined at Nmaximum. This procedure assumes that the correction factor is constant at all gyrations. A part of this study was carried out to compare the correction factors obtained at different gyration levels during compaction of hot mix asphalt and to evaluate the change in correction factor with gyration levels. Specimens were compacted at different gyration levels, and the bulk specific gravity of each was determined at each gyration level. Bulk specific gravities at each of the gyration levels were also obtained by back calculation from bulk specific gravity at Nmaximum. The correction factor was found to decrease and become close to constant at higher gyration levels. At lower gyrations, densities were found to be greater than those obtained by back calculation. It is recommended that mixes be compacted to Ndesign for determination of design asphalt content.
Georgia’s Experience with Recycled Roofing Shingles in Asphaltic Concrete
Authors: Watson Donald E. , Johnson Andrew , Sharma Hem R.
Published: April 2007

Reuse of roofing shingle waste not only minimizes the environmental problems related to the disposal of waste in landfills, but also reduces the amount of virgin asphalt cement and fine aggregate required in hot mix asphaltic concrete (HMAC), thus creating the potential for cost savings. The Georgia Department of Transportation (GDOT) has experimented with the recycling of roofing shingles in HMAC by constructing two test sections in 1994 and 1995. The source of the roofing shingles used in both test sections was waste generated by a roofing manufacturer; this generally consisted of discolored or damaged shingles. One test section was constructed on Chatham Parkway in Chatham County and one on State Route 21 in Effingham County. GAF Building Materials, Inc., located in Savannah, provided the waste shingle material; APAC Georgia, Inc., also located in Savannah, produced and placed these experimental mixtures. To date, both test sections are performing well compared with the unmodified control sections. Based on the performance of these test sections, shingle manufacturing waste is allowed as a recycling material in HMAC, just as reclaimed asphalt pavement is, for GDOT projects. A specification allowing postconsumer roofing shingle waste to be used is also being proposed.
Effect of Tire Rubber Grinding Method on Asphalt-Rubber Binder Characteristics
Authors: West Randy C. , Page Gale C. , Veilleux John G. , Choubane Bouzid
Published: April 2007

The results of a study carried out to evaluate the effect of rubber grinding processes on the properties and characteristics of the resulting asphalt-rubber binder are presented. Several ambient and cryogenic ground tire rubber (GTR) materials were evaluated using measurements of surface areas and bulk densities. The rubber materials were then, respectively, mixed with an AC-30 asphalt; the resulting blends were tested to determine the corresponding viscosity, settlement during storage, and potential for binder draindown. The findings indicate that the asphalt-rubber binders produced with rubber from the different grinding processes have measurable differences in properties and storage characteristics that are critical to the performance of the binder in open-graded mixtures. The wet-ground rubber material had substantially lower bulk densities and larger surface areas than rubber resulting from other grinding methods. GTR materials with greater specific surface areas and more irregularly shaped particles produced asphalt-rubber binders with higher viscosities. Binders with the cryogenic ground rubber had the greatest amount of settlement and the least resistance to draindown.
Relating Laboratory and Field Moduli of Texas Base Materials
Authors: Nazarian S. , Rojas J. , Pezo R. , Yuan D. , Abdallah I. , Scullion T.
Published: April 2007

Resilient modulus of base is an important parameter in the AASHTO pavement design method. However, the manner to determine this parameter is not well defined. Recent efforts in combining the resilient moduli from laboratory testing with those obtained in the field using nondestructive testing devices are presented. Laboratory tests were carried out in two stages. In the first stage, virgin materials from the quarry compacted to optimum moisture content were tested. In the second stage, similar base materials were retrieved from in-service roads. Specimens were prepared and tested at the corresponding field densities and moisture contents. Nondestructive tests were performed with the Falling Weight Deflectometer and the Seismic Pavement Analyzer. Based on tests on 10 different base materials from different parts of Texas, it was concluded that it may be difficult to directly compare moduli from laboratory and field tests; however, they can be combined for effective pavement design.
Experimental Verification of Resilient Deformation for Granular Subgrades
Authors: Ping W. Virgil , Yang Zenghai
Published: April 2007

Results of an experimental program utilizing the repetitive rigid plate load test in a test-pit facility and the laboratory resilient modulus test are presented for five typical subgrades in Florida. The subgrade materials were tested in the test pit under three different moisture conditions, that is, (1) optimum, (2) drained and dried, and (3) soaked. Laboratory resilient modulus tests were conducted on reconstituted soil samples simulating the various moisture conditions. The resilient modulus was significantly affected by the moisture content of granular subgrades. A comparison between the deformations measured from the test-pit test and the deformation calculated from the laboratory test was made. It was experimentally verified that the resilient modulus resulting from the laboratory triaxial test could be used to predict the resilient deformation of pavement subgrade layers.
Prediction of Layer Moduli from Falling Weight Deflectometer and Surface Wave Measurements Using Artificial Neural Network
Authors: Kim Yongon , Kim Y. Richard
Published: April 2007

A new algorithm for predicting layer moduli using measurements from both falling weight deflectometer (FWD) and surface wave tests is presented. This algorithm employs numerical solutions of a multilayered half-space based on Hankel transforms as a forward model and an artificial neural network (ANN) for the inversion process. Phase velocities for frequencies ranging from 10 Hz to 10,000 Hz are calculated using the forward model for varying pavement structures with a range of layer moduli and thicknesses. These phase velocities, along with the layer moduli and thicknesses, are used to train an ANN to backcalculate layer moduli from dispersion curves (i.e., phase velocity versus frequency curves) constructed from the FWD and stress wave test data. To account for the effect of bedrock on the moduli prediction, another network is trained with layer thicknesses and phase velocities for predicting the depth to bedrock. Combining this network with the network for the moduli prediction results in a sequential dispersion analysis technique in which the depth to bedrock predicted from the first network becomes an input to the second network for predicting layer moduli. FWD and stress wave test measurements from an intact pavement and an asphalt overlay over cracked asphalt layer are processed using the sequential dispersion analysis technique and MODULUS 5.0 backcalculation program. Comparison of the results indicates that the dispersion analysis technique yields less variable subgrade moduli and is more sensitive to changes in the asphalt surface layer, because the high-frequency data from the stress wave test is incorporated.
Fatigue Behavior of Rubber-Modified Pavements
Authors: Raad Lutfi , Saboundjian Stephan
Published: April 2007

Over the last 18 years, a number of rubberized pavement projects have been built in Alaska. Initial laboratory and field investigations sponsored by the Alaska Department of Transportation and Public Facilities (AKDOT&PF) and conducted by Raad et al. indicated improved fatigue performance of the rubberized sections in comparison with conventional asphalt concrete pavements. The results of a follow-up investigation to develop design equations for rubberized pavements in Alaska are presented. Laboratory studies were conducted on field specimens using the flexural fatigue test in the controlled-displacement mode. Specifically, the rubberized mixes included asphalt-rubber concrete with AC-2.5 (wet-process) and PlusRide RUMAC with AC-5. Tests were performed for a range of temperatures varying between 22°C and –29°C. Fatigue relationships were developed in terms of repeated flexure strain, dynamic flexure stiffness of the mix, and repetitions to failure. Relationships for the dynamic flexure stiffness as a function of temperature were also developed. Dissipated energy associated with repeated flexure stress and strain was determined and used to assess the damage behavior of conventional and rubberized mixes. The proposed fatigue equations were used to compare the behavior of the rubberized mixes with conventional AC-5 mixes at 20°C and 0°C. Results of the analysis show that at 20°C, asphalt-rubber and AC-5 mixes exhibit essentially similar fatigue resistance, whereas PlusRide has the least fatigue life. However, at 0°C, the fatigue resistance of PlusRide and asphalt-rubber exceeds that of the conventional AC-5 mix. The fatigue equations were also used to compare the fatigue life of conventional and rubberized pavements for different surface layer temperatures and foundation support conditions.
Pavement Distress Under Accelerated Trafficking
Authors: Chen Dar-Hao
Published: April 2007

A test pad was closely monitored for a 6-month period, with 640,000 axle load repetitions applied to the test pavement. The load was applied by the Texas Mobile Load Simulator, a full-scale accelerated loading device. Pavement performance data, such as rutting and cracking, were collected at intervals of 0; 2,500; 5,000; 10,000; 20,000; 40,000; 80,000; 160,000; 320,000; and 640,000 axle repetitions. Falling weight deflectometer (FWD) tests were performed at these same data collection intervals to characterize the structural capacity of the pavement system. Although there is a trend indicating that locations with higher FWD deflection result in higher rutting, a unique relation to predict rutting accurately from the surface deflection alone was not found in the study. The back-calculated asphalt concrete pavement moduli were reduced by 50 percent of the original value at the end of 320,000 repetitions. However, the test was not terminated until 640,000 repetitions, when moduli were reduced to 40 percent of the original values. Both FWD deflection and percent of cracked area share the same trend; the left wheelpath had higher initial FWD deflections and later yielded a higher percentage of cracked area. Approximately 50 percent of the wheelpath area was cracked at the end of 80,000 repetitions, as measured by counting the number of cracked squares on a 100 mm by 100 mm grid. However, most of the cracks were hairline cracks. The percentage of cracked area is strongly related to the grid size used. A grid size of 100 mm by 100 mm has been recommended by other researchers and was adopted in this study. Eighty-five percent and 90 percent of the area in the wheelpaths was cracked at the end of 320,000 and 640,000 repetitions, respectively. These numbers are higher than those adopted by the Asphalt Institute, which defines failure as 45 percent cracking in the wheelpath.
Correction of Field Skid Measurements for Seasonal Variations in Texas
Authors: Jayawickrama P. W. , Thomas B.
Published: April 2007

Findings are presented from a research study conducted in Texas to determine the significance of seasonal variation in skid measurements. Six bituminous highway pavement sections, two each from three different climatic regions, were monitored over a period of more than 18 months. Monitoring included collection of wet pavement skid resistance data using a locked-wheel skid trailer that met the specifications of ASTM E-274. These measurements were made at biweekly intervals in two of the three climatic regions and at monthly intervals in the remaining climatic region. The necessary climatic data were obtained from nearby National Climatic Data Centers. The data obtained indicated that significant variation in skid numbers occurs from one day of measurement to another. The maximum variations observed were on the order of 10 to 12 skid numbers. Furthermore, there were strong indications that the variations occurred in response to changes in temperature and precipitation. Finally, three methods of normalizing the skid data to obtain the true mean skid number of the pavement were evaluated. The first of these was a linear regression model based on rainfall, temperature, and other variables. The second was a nonlinear regression model based on Julian calendar day only. The third approach examined the possibility of using multiple skid measurements to achieve a desired level of accuracy. The advantages and disadvantages of each method are discussed.
Friction and Surface Texture Characterization of 14 Pavement Test Sections in Greenville, North Carolina
Authors: Corley-Lay Judith B.
Published: April 2007

Three locked-wheel skid trailers, International Cybernetics Corporation (ICC) Model MOR 5041 and K. J. Law Models M 1270 and M 1290, were tested at three speeds on 14 test sections located in Greenville, North Carolina. The test sections included a heavy-duty surface course, polymer-modified heavy-duty surface course, rubber-modified heavy-duty surface course, heavy-duty surface course with carbon black, stone mastic with fibers, polymer-modified stone mastic, and large-stone surface course. Multivariate regression analysis of friction number versus speed for the three test vehicles was performed. Despite having been load cell calibrated 1 day before testing, the ICC MOR 5041 results were statistically different from those of the other skid trailers on all but one test section. The two K. J. Law skid trailers were statistically different from each other, either on intercept or slope, on more than half of the test sections. Each individual skid trailer provided repeatable results with a standard deviation of about 2 when testing was done at 64 km/h, with a higher standard deviation for testing at lower speed. The frictional resistance of the test sections was compared by ranking frictional number at 64 km/h and rate of decline of friction number with speed. The best frictional performance was provided by the heavy-duty surface course and the large-stone surface course, and stone mastic with fibers and stone mastic with polymer were ranked poorest. None of the test sections had an average friction number less than 40, even when tested at 80 km/h.
Road Traffic Violations and Seat Belt Use in Kuwait: Study of Driver Behavior in Motion
Authors: Koushki P. A. , Ali S. Y. , Al-Saleh O.
Published: April 2007

Despite heavy investments in the transportation infrastructure and the existence of a young vehicle fleet, road safety in the affluent State of Kuwait continues to decline. Poor driver behavior and lack of enforcement of traffic regulations are believed to be the main causes of the unsafe driving environment. The findings of a research project designed to examine the relationship between seat belt use and road traffic violations in Kuwait are reported. The traffic violation behavior of 821 randomly selected drivers was recorded while the drivers were followed to their destinations. Factors of nationality, age range, gender, roadway type, vehicle type, time of day, trip time, and trip distance were also monitored. The average sample nonuser of seat belts made more than twice as many violations both per kilometer of travel and per minute of trip time than did seat belt users. Seat belt nonusers and young drivers (especially Kuwaitis) were found to be overrepresented in the violating groups, and discriminant analysis successfully discriminated between the high and low violators of traffic rules.
Red-Light Running and Sensible Countermeasures: Summary of Research Findings
Authors: Retting Richard A. , Williams Allan F. , Greene Michael A.
Published: April 2007

Deliberate running of red lights is a common and serious violation that contributes substantially to the more than 1 million motor vehicle collisions that occur at traffic signals each year. Urban-based highway safety research has examined various aspects of the red-light running problem, including the contribution of red-light violations to motor vehicle crashes, the frequency of red-light running, characteristics of red-light runners, and the influence of signal timing on red-light running behavior. A brief summary of recent research efforts to examine the problem of red-light running is provided, and the use of countermeasures, including red-light cameras, to reduce the problem is discussed.
Evaluation of Speed Limits in Kentucky
Authors: Agent Kenneth R. , Pigman Jerry G. , Weber Joel M.
Published: April 2007

The objectives were to examine current criteria and procedures used for setting speed limits and to determine appropriate speed limits for various types of roads. The study involved a review of literature, collection and analysis of speed data, and collection and analysis of accident data. The speed data included moving speed data on various highway types and a comparison of speed data before and after speed limit changes. Accident data were collected at locations where speed limits were changed and also on sections of adjacent Interstates with different speed limits. The speed data indicate that a large percentage of vehicle speeds exceed posted speed limits, with the highest percentage being on urban Interstates and two-lane parkways. The speeds for trucks were slightly lower than for cars. A comparison of speed data at locations where speed limits were changed showed only slight differences. A comparison of accident rates at adjacent sections of Interstate where the speed limit was 88.6 km/hr (55 mph) and 104.7 km/hr (65 mph) did not find a substantial difference in the total, injury, or fatal accident rates. Except where legislatively mandated speed limits apply, the 85th-percentile speed should be used to establish speed limits. Maximum limits are given for various types of roadways. Different speed limits for cars and trucks are recommended for some roadways. An engineering study must be conducted before the speed limit should be changed for any specific section of roadway.
Survey of Truck Drivers’ Knowledge and Beliefs Regarding Driver Fatigue
Authors: Van Hemel Susan B. , Rogers William C.
Published: April 2007

A survey was distributed to about 25,000 truck drivers in the United States and Canada to determine their knowledge of several fatigue-related topics; 4,833 responses were received and tabulated. Analysis by topic area indicated that the following topics are not well understood by respondents and should be considered for special emphasis in fatigue outreach and education programs. Sleep disorders, especially sleep apnea, appear to be poorly understood by the respondents, and younger drivers are least informed on this topic. Many respondents are not aware that apnea is treatable. Napping is recognized as an effective short-term countermeasure to fatigue by fewer drivers than might be desired. Those who do use napping as a fatigue countermeasure believe it is very helpful. Sleep requirements may be underestimated by many drivers. About 25 percent of the respondents believe that 5 to 6 hr of sleep per night is enough to maintain alertness. Circadian rhythm effects are not fully understood by the respondents, especially effects on mood and performance efficiency. Caffeine and its effects on the body are misunderstood by many drivers. A fairly large proportion of respondents appear unaware of the limitations on caffeine’s stimulant effects and of possible side effects of caffeine overuse. Melatonin, a hormone, may be another substance the drivers need to know more about. Many drivers did not respond to the item on melatonin safety, and many others responded incorrectly.
Commercial Vehicle Driver Family Issues Assessment
Authors: Hill Melinda J. , Hudson Nancy W. , Lantz Brenda M. , Griffin Gene C.
Published: April 2007

The dissatisfaction of truck drivers associated with issues related to the family is examined. This dissatisfaction is seen as a major reason for high turnover rates in the trucking industry. The nature of commercial vehicle driver work and family environments is more clearly defined through mail survey questions asked of both the driver and their spouse/partner. Specific questions in the survey address work concerns, family concerns, decision making, informational needs, communication, and leisure time. Methods to apply this information to programs of intervention and support useful to commercial vehicle companies are identified. Results indicated that family-related information would help support drivers and their families. In addition, a literature review discusses job characteristics of drivers, describes stressors for the families, and identifies possible coping skills and intervention methods.
End User Perspectives of a Smart Card-Based Commercial Driver’s License
Authors: Marwah Sanjay , Gifford Jonathan L. , Maggio Mark , Stough Roger R.
Published: April 2007

The commercial vehicle operations (CVO) sector is considering adoption of several smart card technologies. Previous research on intelligent transportation systems (ITS) and technology usage in the trucking industry focused primarily on technology adoption issues from the perspective of state and federal regulatory agencies and motor carrier companies. To extend this research, interviews with truck drivers were conducted to determine direct end user perceptions and needs. Institutional issues remain the biggest barriers to adoption in the near future. Issues for truck drivers include privacy, operation and management of a smart commercial driver’s license (CDL) system, role of a smart CDL in ITS/CVO user service areas and links with other relevant information and trucking technologies, addition of other applications aside from licensing, and regulatory burden on carriers and drivers. Applications such as emergency contact and organ donor were strongly supported, but drivers were cautious about implementation of smart CDLs and their potential benefits. As with other computer and electronic technologies, use and experience will influence attitudes and views toward these technologies. Strategies and opportunities to address these concerns are outlined.
Results from Minnesota/Wisconsin Automatic Out-of-Service Verification Operational Test
Authors: Smith Robert L. , Huang Wen-Jing
Published: April 2007

A project was designed to enhance the ability of inspectors at fixed safety and weight stations (scales) to identify “out-of-service” (OOS) commercial vehicles and drivers by using advanced video-based license plate scanners linked to database software on a personal computer, the MOOSE system. In Wisconsin the results of safety inspections at the scales are stored in real time on a central computer database. This includes commercial vehicles and drivers placed OOS because of major safety violations. The primary goals were to increase the effectiveness of OOS enforcement efforts, establish a bistate enforcement program, and identify future applications. The technology was tested on a corridor involving three scales in Wisconsin and one in Minnesota on westbound I-90/I-94. The MOOSE system did identify a large number of OOS vehicles and drivers, but upon reinspection, almost no current OOS violations were found. The MOOSE system was successfully implemented at the Minnesota scale, but, as in Wisconsin, very few current OOS violations were identified. Because the Minnesota scale operates 24 hr/day, drivers coming from Wisconsin who are still OOS will probably use bypass routes. The greatest potential benefit from the MOOSE system is likely to be from linking the license plates to a new system that provides safety rating scores. Inspectors could then select vehicles for inspection that have a higher probability of being OOS or having other safety violations.
Evaluation of California Motorcyclist Safety Program
Authors: Billheimer John W.
Published: April 2007

The California Motorcyclist Safety Program (CMSP) is a legislatively mandated, statewide program that has trained more than 100,000 motorcyclists in the 10 years since its implementation in July 1987. The program is mandatory for riders under 21 seeking a California motorcycle license. The current evaluation traces motorcycle accident trends before and after the formation of the CMSP, compares accident trends in California with those in the remainder of the United States, and analyzes the riding records of matched pairs of 2,351 trained and untrained Southern California riders. Analyses of statewide accident trends indicate that fatal motorcycle accidents have dropped 69 percent since the introduction of the CMSP, falling from 840 fatal accidents per year in 1986 to 263 in 1995. If accident trends in California had paralleled those in the rest of the United States over this period, the state would have experienced an additional 124 fatalities per year. In the case of novice riders with less than 805 km (500 mi) of prior experience, a matched-pair analysis indicates that trained riders experience fewer than half the accident rates of their untrained counterparts for at least 6 months after training. Beyond 6 months, riding experience begins to have a leveling effect on the differences between the two groups. In the case of riders with more than 805 km (500 mi) of experience prior to training or interviewing, no significant differences in accident rates were detected between the two groups, either before or after riders took the basic training course. There was no evidence that riders electing to enter a safety course voluntarily rode any more safely than their untrained counterparts before taking training.
Real-Time Measurement of Lead in Ambient Air During Bridge Paint Removal
Authors: Zamurs John , Bass Jonathan , Williams Bradley , Fritsch Ruth , Sackett Donald , Heman Robert
Published: April 2007

Air quality monitoring involving traditional high-volume air sampling for particulate and lead in association with removal of lead-based paint by abrasive blasting from bridges has consistently been associated with high cost and significant lag time between the time of sample collection and the availability of useful results to project personnel. On the basis of the results of two analytical studies conducted in association with air quality monitoring performed on New York State Department of Transportation bridge painting projects involving abrasive blasting, X-ray fluorescence (XRF) technology can provide useful lead concentration results on a realtime basis. Feasibility and field studies conducted comparing results of traditional laboratory filter analysis for lead and filter measurement by XRF indicate reliable and practical application of this technology for evaluating the effectiveness of abrasive blasting containment.
Reducing Particulate Matter and Oxides of Nitrogen Emissions from Heavy-Duty Vehicles: The Urban Bus Case
Authors: Schimek Paul
Published: April 2007

The 1990 Clean Air Act Amendments mandated stricter emissions standards for heavy-duty vehicles. One category of heavy-duty vehicles, urban transit buses, constitutes a highly visible source of pollutant emissions and must meet even more stringent standards. In response, engine manufacturers have produced diesel engines that produce virtually no black smoke and emit several times less particulate matter (PM) than older engines. The tighter PM emissions standards that apply to urban transit buses only were found to be cost-effective ($4,600 to $6,300 per Mg of PM reduced) compared with other control strategies. The Urban Bus Retrofit/Rebuild Program was found to be somewhat less cost-effective ($6,900 to $42,000 per Mg). Both of these programs could be extended to other heavy-duty vehicles. However, the use of compressed natural gas (CNG) in transit buses was found to have a costeffectiveness of $0.9 million to $1.8 million per Mg of PM. Replacing older diesel engines with low-emission diesels is the most cost-effective way to reduce transit bus emissions. By purchasing more clean diesels instead of fewer cleaner CNG buses, transit agencies can produce greater reductions in fleetwide emissions. In fact, the transit agency in this study with the most alternative-fuel buses has the highest fleetwide PM emissions rate. It is premature to expand the alternative-fuel transit bus fleet beyond the experimental level. Regulatory policy should be reassessed as the understanding of the link between diesel emissions and health effects improves.
Modeling Enleanment Emissions for Light-Duty Vehicles
Authors: An Feng , Barth Matthew , Scora George , Ross Marc
Published: April 2007

A comprehensive modal emissions model for light-duty cars and trucks is being developed under the sponsorship of NCHRP Project 25-11. Model development has been described previously for vehicles operating under stoichiometric and enrichment conditions. A modal emissions model is presented for vehicles operated under enleanment conditions. Enleanment typically occurs with sharp deceleration or load reduction events, and sometimes during long deceleration. Under enleanment conditions, the air/fuel ratio is lean and incomplete combustion or misfire occurs. Preliminary research indicates that enleanment emissions (particularly for hydrocarbons) contribute significantly to a vehicle’s overall emissions. An enleanment emissions module has been developed on the basis of second-by-second emission measurements generated at the College of Engineering—Center for Environmental Research and Technology’s vehicle testing facility using the Federal Test Procedure, US06, and a specially designed modal emission cycle (MEC01). On the basis of more than 200 vehicles tested and modeled, lean-burn hydrocarbon emissions (HClean) account for 10 to 20 percent of the overall HC emissions under the various test cycles. HClean emission contributions vary greatly from vehicle to vehicle, ranging from near 0 to more than 30 percent of total HC emissions of individual vehicles. After detailed analysis of the second-by-second emission data over the modal emission cycle MECO1, it was found that enleanment hydrocarbons emissions are mostly associated with rapid load reduction events and long deceleration events. The former is most likely to cause extremely high levels of HC as short spikes, and the latter is mostly associated with longer-lasting HC puffs. A methodology has been developed to characterize and model enleanment hydrocarbons emissions associated with these two events. The model estimates are compared with measurements, with encouraging results.
High-Emitting Vehicle Characterization Using Regression Tree Analysis
Authors: Wolf Jean , Guensler Randall , Washington Simon , Bachman William
Published: April 2007

A small fraction of motor vehicles on the roadway emit a disproportionate fraction of pollutant emissions, especially for carbon monoxide and hydrocarbons. Generally, these “high emitters” or “super emitters” exhibit higher emissions rates under all operating conditions than do “normal emitters.” Since the instantaneous emissions response between normal- and high-emitting vehicles can differ by one or more orders of magnitude, so do their average emissions over a “typical” trip. Identifying the proportion of normal- and high-emitting vehicles in an urban area and quantifying their emissions is vital for accurate emission inventory accounting. A methodology by which high and normal emitters can be classified is presented. Unlike previous emitter classification approaches, the approach is data driven and relies entirely on hot-stabilized emissions results. A statistical classification scheme, better known as hierarchical tree based regression, is used to separate vehicles into homogenous emitter categories. The approach is shown to have a number of advantages. First, it is flexible with respect to both the number of classes and types of variables used to identify classes. Second, it considers the influence of a large number of vehicle and technology attributes on emitter status. Third, it ensures that the highest emitters can be isolated from the normal emitters, so that separate emission rate models can be developed for these vehicles. Finally, the approach does not combine the effects of starts and hot-stabilized operations within the definition of high emitter, leading to a classification scheme whereby vehicles with poor start emissions characteristics will not be incorrectly classified as vehicles with poor hot-stabilized emission characteristics.
Time Period and Vehicle Class Highway Assignment for Air Quality Conformity Evaluation
Authors: Eash Ronald
Published: April 2007

Regions that have not attained the National Ambient Air Quality Standard for ozone must demonstrate that their transportation plans and programs conform to a state implementation plan to meet national air quality standards. Vehicle emissions are estimated by metropolitan planning organizations for these conformity evaluations, and the state of the practice is to calculate vehicle emissions from the vehicle distances traveled at different speeds. A highway assignment procedure for air quality conformity has been developed at the Chicago Area Transportation Study (CATS) to provide more detailed estimates of how vehicle distances and speeds vary by time of day and by type of vehicle. The assignment procedure prepares tables of vehicle distances traveled by speed for six classes of vehicles and eight time periods during a typical workday. The eight time period assignments more correctly depict network congestion than the peak—off-peak or average daily highway assignments previously carried out by CATS. The separate vehicle class link volumes reflect the geographic and time period distribution of trips by light- and heavy-duty vehicles. The conformity assignment procedure and the problems encountered in adapting existing highway assignment practices to allow for additional time periods and vehicle classes are outlined. Some conformity assignment results are compared with a daily average assignment to illustrate how the time period assignment procedure affects vehicle emission estimates.
Project Level Carbon Monoxide Hot-Spot Analysis for Level of Service D Intersections
Authors: Meng Yu , Niemeier Debbie A.
Published: April 2007

Hot-spot [localized carbon monoxide (CO) and particulate matter (PM10) violations] analysis is often required by the Environmental Protection Agency (EPA) to determine project level air quality conformity of transportation projects in accordance with state implementation plans. EPA uses intersection level of service (LOS) as one of its major criteria for identifying potential CO hot spots. EPA’s 1992 Guideline for Modeling CO from Roadway Intersections states that hot-spot analysis is not required for those intersections operating at LOS A, B, or C (i.e., these intersections are automatically eliminated as potential CO hot spots), whereas intersections operating at LOS D or worse must undergo detailed CO concentration analysis. Of all possible LOS D intersections, clearly only a few will actually require detailed modeling of CO concentrations. A new screening methodology that introduces the concept of meteorological situation-orientated reference charts is presented. Variations on the basic reference charts can incorporate such effects as signal type (e.g., pretimed versus actuated) and future fleet characteristics. Once the desired reference charts have been developed, to use them the analyst needs only to identify the applicable reference chart on the basis of the location of the project at hand and an approximate background concentration. The proposed screening methodology should save both effort and money often wasted on the redesign of intersections that are predicted to be hot spots at the time of air quality conformity analysis and when detailed air quality analysis of LOS D intersections is undertaken for intersections that are unlikely to be CO hot spots.
Emissions Reduction Potential of the Congestion Mitigation and Air Quality Improvement Program: A Preliminary Assessment
Authors: Adler Ken , Grant Michael , Schroeer William
Published: April 2007

The Congestion Mitigation and Air Quality (CMAQ) program provides funds to states for projects designed to help attain the national ambient air quality standards. However, to date there has been no attempt to quantify the national emissions effects of the CMAQ program or its potential. States are requested to provide estimates of emissions reductions associated with projects funded by the CMAQ program to FHWA. These reports provide a rich source of data for analysis of the CMAQ program, although the data have various limitations. A methodology to estimate potential effects of the CMAQ program on emissions of volatile organic compounds, oxides of nitrogen, and carbon monoxide using data provided by the states to FHWA is presented. Using this methodology, a preliminary assessment of the emissions effect of the CMAQ program from its inception in 1992 through 2005 is presented. It is suggested that the CMAQ program is playing a significant role in reducing emissions nationwide. Emissions estimates are sensitive to assumptions about project cost-effectiveness and years of effect. In addition, various limitations in the national database of CMAQ projects are noted. The use of consistent methodologies for estimating the effects of programs nationwide is recommended to improve the accuracy of national emission reduction estimates.
Air Quality Effects of Travel Changes
Authors: Zavattero David A. , Ward Janice A. , Strong Christopher K.
Published: April 2007

Travel behavior in northeastern Illinois was examined for the 20-year period between 1970 and 1990 by conducting a comparative analysis of data from the Chicago Area Transportation Study 1970 Home Interview and the 1990 Household Travel Surveys. This study identified regional travel conditions and needs and provided an overview of the changes that have occurred because of population and employment growth and behavioral shifts. By understanding travel behavior and patterns in the region and resulting congestion and air quality effects, travel reduction strategies could be developed to promote mobility and meet environmental objectives. The analysis offers insight into travel purpose, mode, location, and length while identifying characteristics of the population making those trips. Changes in travel during the 1970 to 1990 period include increased total daily trips, person miles, and private automobile use, primarily single-occupant vehicle trips; substantial growth in suburban travel; increased work trips, transit and automobile trip lengths, and trip-chaining; reduced passenger trips and automobile occupancy rates; and increased suburban transit ridership. These travel changes have increased traffic congestion and affected air quality. Advances in technology have increased vehicle efficiency. The relative contributions to emissions changes that can be attributed to technology and to underlying behavioral changes are examined. Transportation management strategies can be applied to increase the efficiency of transportation facilities and further improve regional air quality.
Analysis of the Cost-Effectiveness of Motor Vehicle Inspection Programs for Reducing Air Pollution
Authors: Lachance Laura C. , Mierzejewski Edward
Published: April 2007

Motor vehicle inspection programs (MVIPs) are used extensively by many communities in the United States as a means to reduce mobile source emissions. In 1992, Florida initiated a motor vehicle inspection program for six counties that were identified as nonattainment areas for ozone pursuant to the Clean Air Act Amendments of 1990. The costeffectiveness of Florida’s motor vehicle inspection program in reducing emissions is evaluated, and the results are compared with the costeffectiveness of other MVIP technologies that are available as alternatives to Florida’s current program. Five combinations of current MVIP technologies were chosen as the alternatives for analysis that represent the range of options available for a motor vehicle inspection program. The results of the cost-effectiveness analysis indicate that the program including the technology of Accelerated Simulation Mode is the most cost-effective of all of the alternatives presented. This program is much more cost-effective in reducing pollutants than the current inspection program in Florida, an annual idle test. In addition, this program is estimated to eliminate more absolute megagrams (tons) of volatile organic compounds and nitrogen oxides. The legislature of Florida has continually examined the issue of continuing or changing the motor vehicle inspection program in Florida. However, no changes have been made to the program since its inception in 1992. The cost-effectiveness comparisons of MVIPs could be useful to other communities searching for costeffective methods of reducing mobile source emissions.
Assessment of Capital Requirements for Alternative Fuels Infrastructure Under the Partnership for a New Generation of Vehicles Program
Authors: Stork Kevin , Singh Margaret , Wang Michael , Vyas Anant
Published: April 2007

An assessment of the capital requirements associated with six different fuels in light-duty vehicles being developed by the Partnership for a New Generation of Vehicles to achieve tripled fuel economy is presented. The six fuels include two petroleum-based fuels (reformulated gasoline and low-sulfur diesel) and four alternative fuels (methanol, ethanol, dimethyl ether, and hydrogen). Estimates of the cumulative capital needs for establishing fuel production and distribution infrastructure to accommodate the fuel needs of tripled fuel economy (3X) vehicles are developed. Two levels of fuel volume—11 000 m3 (70,000 barrels) per day and 254 000 m3 (1.6 million barrels) per day—were established for meeting 3X-vehicle fuel demand. As expected, infrastructure capital needs for the high fuel demand level are much higher than for the low fuel demand level. Between fuel production infrastructure and distribution infrastructure, capital needs for the former far exceed those for the latter. Among the four alternative fuels, hydrogen bears the largest capital needs for production and distribution infrastructure.
Determinants of Alternative Fuel Vehicle Choice in the Continental United States
Authors: Tompkins Melanie , Bunch David , Santini Danilo , Bradley Mark , Vyas Anant , Poyer David
Published: April 2007

The ongoing investigation into the determinants of alternative fuel vehicle choice is described. A stated preference vehicle choice survey was conducted for the 47 continental U.S. states, excluding California. The national survey is based on, and is an extension of, previous studies on alternative fuel vehicle choice for the state of California conducted by the University of California’s Institute of Transportation Studies. Several vehicle choice models are being developed on the basis of the survey information. Preliminary model estimates using the national survey alone plus estimates for a "pooled" model using both California and national survey information are presented.
Sensitivity of Network-Level BMS MR&R Policies to Variations in Cost, Transition Probability, and Discount Factor
Authors: Adams Teresa M. , Robert Sianipar P.
Published: April 2007

A sensitivity analysis of the recommendations obtained from the maintenance, repair, and rehabilitation (MR&R) optimization model of the Pontis bridge management system (BMS) to changes in Wisconsin’s estimates of MR&R costs, transition probabilities, and discount factor is presented. The scope includes the MR&R actions for 25 bridge elements in Wisconsin. The analysis is based on scenarios of cost and transition probabilities that represent a range of low- to high-cost projects and slow to fast element deterioration. The potential cost savings per element from adopting special policies on extreme high- and low-cost projects were estimated. The analysis identified the MR&R actions that are sensitive to changes in cost or transition probability, the MR&R actions that are never recommended, and the cost and transition scenarios for which the optimal policy is to do nothing until failure. The optimal policies recommended by the BMS and the current practice at Wisconsin District 1 were compared. Recommendations for improving Wisconsin’s MR&R cost database are presented.