bluuebunny/crossref_metadata_2025 huggingface dataset:
Feature Selection for Intrusion Detection with Neural Networks and Support Vector Machines
Authors: Mukkamala Srinivas , Sung Andrew H.
Published: April 2007

Computational intelligence (CI) methods are increasingly being used for problem solving, and CI-type learning machines are being used for intrusion detection. Intrusion detection is a problem of general interest to transportation infrastructure protection, since one of its necessary tasks is to protect the computers responsible for the infrastructure’s operational control, and an effective intrusion detection system (IDS) is essential for ensuring network security. Two classes of learning machines for IDSs are studied: artificial neural networks (ANNs) and support vector machines (SVMs). SVMs are shown to be superior to ANNs in three critical respects of IDSs: SVMs train and run an order of magnitude faster; they scale much better; and they give higher classification accuracy. A related issue is ranking the importance of input features, which is itself a problem of great interest. Since elimination of the insignificant (or useless) inputs leads to a simplified problem and possibly faster and more accurate detection, feature selection is very important in intrusion detection. Two methods for feature ranking are presented: the first one is independent of the modeling tool, while the second method is specific to SVMs. The two methods were applied to identify the important features in the 1999 Defense Advanced Research Projects Agency intrusion data set. It was shown that the two methods produce results that are largely consistent. Experimental results indicated that SVM-based IDSs with a reduced number of features can deliver enhanced or comparable performance. An SVM-based IDS for class-specific detection is proposed.
Measures of Effectiveness for Passenger-Baggage Security Screening
Authors: Leone Kelly , Liu Rongfang (Rachel)
Published: April 2007

One of the most challenging tasks of the Aviation and Transportation Security Act of 2001 is to meet the goal of performing explosive detection system (EDS) screening on 100% of checked baggage by the end of calendar year 2002. Accomplishing this goal within the imposed deadline and within the typically tight space constraints of airport terminals will require significant changes in the way airlines and airports manage passengers and their baggage. One of the up-front keys to integrating 100% checked-baggage screening into airports is to identify realistic throughput rates of various EDS machines available to Transportation Security Administration (TSA) planners. Some of the issues associated with the implementation of EDS equipment are discussed, and an analysis is performed on the throughput of the equipment, using modeling and discrete event-simulation tools. One conclusion of the analysis is that a significant difference exists between the scan rate and the effective throughput rate for the InVision CTX5500, one of the tested EDS machines. This finding is extremely important for TSA planners, who are determining the number of EDS machines to buy and deploy at all 429 U.S. commercial airports. The deployments are based on passenger demand at peak hours of the day. Matching this relatively high-volume operation against the slow processing rate of a standalone EDS will generate large passenger queues unless multiple machines are installed to provide an acceptable level of customer (passenger) service. As a result, the effective throughput rate, not the machine scan rate, should be used in determining the number of EDS machines to install at a particular airport.
Whitetopping and Hot-Mix Asphalt Overlay Treatments for Flexible Pavement: Minnesota Case History
Authors: Burnham Tom , Rettner David
Published: April 2007

In 1993, two hot-mix asphalt and four whitetopping overlay test sections were constructed on low-volume road TH 30 in southern Minnesota. A study was undertaken to examine the performance and costs associated with the test sections after 9 years of service. The field testing and evaluation are described, and the costs incurred through 2001 are tabulated. The hot-mix asphalt overlay test sections are performing up to their design expectations. Routine preventive maintenance has been applied to both hot-mix asphalt test sections, adding to their long-term cost of operation and ownership. The whitetopping test sections are performing very well at the midpoint of their design lives of 20 years. Most distresses to date are related to poor construction and materials rather than inherent design features. Some random longitudinal cracking has occurred in areas of the whitetopping control section. The doweled test section has numerous distressed transverse joints caused by dowels near the surface of the slabs. There is virtually no faulting of the transverse joints, and the ride quality has stabilized. No maintenance has been performed on the whitetopping sections through 2001. As of 2002, the most economical overlay design in this study is a 6-in.-thick bonded whitetopping. On the basis of recent observations, it appears that whitetopping performs well and is an economical option for rehabilitation of low-volume roads in Minnesota.
Precast Prestressed Concrete Pavement Pilot Project near Georgetown, Texas
Authors: Merritt David K. , McCullough B. Frank , Burns Ned H.
Published: April 2007

The use of precast concrete is rapidly becoming a viable method for repair and rehabilitation of portland cement concrete pavements, with several projects under construction or in development throughout the United States. Construction with precast concrete offers numerous benefits over conventional cast-in-place pavement construction. Most notable is how quickly a precast pavement can be opened to traffic. Precast panels can be placed during overnight or weekend operations and opened to traffic almost immediately. In addition, because precast panels are cast in a controlled environment, the durability of a precast pavement is also improved. In March 2002, the Texas Department of Transportation completed construction of a precast pavement pilot project aimed at testing and further developing a precast pavement concept developed by the Center for Transportation Research at The University of Texas at Austin. This project was constructed on a section of frontage road along Interstate 35 near Georgetown, Texas. The project incorporated the use of posttensioned precast concrete panels. The panels were posttensioned in place not only to tie all the panels together but also to reduce the pavement thickness required and improve durability. The finished pavement demonstrated not only the viability of precast pavement construction but also the benefits of incorporation of posttensioning. Although the project was constructed without the time constraints and complexities that will eventually need to be considered for precast pavement construction, it ultimately helped to develop viable construction procedures for future precast prestressed concrete pavements.
Evaluation of Applicability of Ultrathin Whitetopping in Florida
Authors: Kumara Wasantha , Tia Mang , Wu Chung-Lung , Choubane Bouzid
Published: April 2007

A three-dimensional (3-D) finite element model for stress analysis of pavements with ultrathin whitetopping (UTW) under critical loading conditions was developed. The 3-D model developed was used to analyze the UTW test pavement sections at the Ellaville Weigh Station in Florida, which had less than satisfactory performance. The poorly performing UTW sections at the Ellaville Weigh Station were found to have relatively higher maximum computed stresses under critical loading conditions, which appeared to explain their poor performance and high percentages of cracked slabs. The 3-D model developed was also used to perform a parametric analysis to determine the effects of asphalt thickness, asphalt modulus, concrete thickness, concrete modulus, base stiffness, subgrade stiffness, slab dimension, temperature differential in the concrete, and applied load on the maximum stresses in UTW pavements under typical Florida conditions.
Precast Concrete Slabs as Full-Depth Repairs: Michigan Experience
Authors: Buch Neeraj , Barnhart Vernon , Kowli Rahul
Published: April 2007

Continued efforts are being made to expedite the construction of durable concrete repairs. In the recent past considerable attention has been given to the use of precast concrete as an alternative to conventional full-depth repair. The use of precast portland cement concrete panels eliminates the time required for curing and offers numerous other benefits, such as an excellent quality of concrete (strength and durability), minimal variability in slab thickness, and minimal negative impacts from built-in curl. In October 2001 and summer 2002, Michigan State University, in cooperation with the Michigan Department of Transportation, installed 21 precast full-depth patches along I-94 BL in Benton Harbor, Michigan, and I-196 in South Haven, Michigan. The construction and performance monitoring protocols for the precast panels placed along I-94 BL are documented. The results from this pilot study will facilitate effective technology transfer to other state agencies contemplating the use of this technology.
Performance of Flexible Pavement Rehabilitation Treatments in the Long-Term Pavement Performance SPS-5 Experiment
Authors: Hall Kathleen T. , Correa Carlos E. , Simpson Amy L.
Published: April 2007

The results of a study conducted to assess the relative performance of different flexible pavement rehabilitation treatments, including the influence of pretreatment condition and other factors, are presented. The data used in the study were drawn from the Long-Term Pavement Performance Studies' Specific Pavement Study (SPS) SPS-5 and General Pavement Study (GPS) GPS-6B experiments. The rehabilitation treatments used in the SPS-5 experiment are 2- and 5-in. overlays with virgin or recycled asphalt concrete mixes with or without preoverlay milling. Overlay thickness and preoverlay roughness levels were the two factors that most influenced the performance of the asphalt overlays of asphalt pavements in the SPS-5 experiment with respect to roughness, rutting, and fatigue cracking. Over the long term, the 5-in. overlays outperformed the 2-in. overlays with respect to roughness, rutting, and fatigue cracking. Overlay mix type (virgin versus recycled) and preoverlay preparation (with or without milling) had slight and inconsistent effects. The average initial postoverlay international roughness index of an asphalt overlay of an asphalt pavement was found to be 0.98 m/km. The data show a slight but statistically significant tendency for asphalt pavements overlaid when they were rougher to have more initial roughness after overlay than asphalt pavements overlaid when they were smoother. The data show that, on average, about 6 mm of rutting develops in the first year or so after placement of an asphalt overlay of an asphalt pavement. This is presumably due to compaction of the mix by traffic and appears to be independent of the overlay thickness, mix type, preoverlay preparation, and preoverlay rutting level.
Laboratory Performance Testing for National Center for Asphalt Technology Pavement Test Track
Authors: Powell R. Buzz
Published: April 2007

An experimental facility has been constructed near the campus of Auburn University in Alabama for the purpose of conducting research to extend the lives of flexible pavements. Experimental sections on the 2.8-km Pavement Test Track are cooperatively funded by external sponsors, most commonly, state departments of transportation, with operation and research managed by the National Center for Asphalt Technology (NCAT). Forty-six different flexible pavements were installed at the facility, each at a length of 61 m. Materials and methods unique to the section sponsors were imported during construction to maximize the applicability of the results. A design lifetime of truck traffic is now being applied over a 2-year period, with field performance documented weekly. Sponsors typically compare the performance of two or more sections constructed with different materials or by different methods to obtain information that can be used to build future pavements with the greatest amount of rut resistance. In addition to assessing alternatives for sponsors, NCAT is responsible for guiding the overall effort in a direction that will address policy issues for the highway industry as a whole. Specifically, laboratory methods that have the potential to predict rutting when they are used before and during construction are being compared with field performance for every experimental mix so that the most suitable method(s) can be recommended. Results from loaded wheel testing are presented to encompass the empirical approach, while results from shear and creep testing facilitate mechanistic analyses. The success of each method will ultimately be measured by comparing the performance in the laboratory with the performance on the experimental roadway.
Performance of Dowel Bar Retrofitted Concrete Pavement Under Heavy Vehicle Simulator Loading
Authors: Harvey John T. , Popescu Lorina , Ali Abdikarim , Bush David
Published: April 2007

The California Department of Transportation uses dowel bar retrofit (DBR) as a rehabilitation strategy for concrete pavements. Two test sections were retrofitted with dowel bars and a third section was designated as a control on US-101 near Ukiah, California. All three sections were subjected to accelerated pavement testing by using the Heavy Vehicle Simulator (HVS). The results obtained with the HVS demonstrated a large improvement in load transfer efficiency (LTE) and decreases in maximum vertical deflections and vertical deflection differences from DBR. LTE was not damaged by trafficking on the sections with DBR and was less sensitive to temperature changes than the control section. Falling weight deflectometer testing showed damage to the interlock at the joint on the control section and no damage on the sections with DBR. Joint and crack deflections and deflection differences increased with trafficking. A total equivalent loading of approximately 11,000,000 equivalent single-axle loads was applied to each of the sections with DBR without failure occurring.
Spacing of Law Enforcement Pullout Areas in Highway Work Zones
Authors: Schrock Steven D. , Ullman Gerald
Published: April 2007

Law enforcement presence in work zones has long been recognized as one of the most effective speed-reduction methods available to transportation officials. Unfortunately, the design of many work zones makes effective enforcement difficult. Work zones that have no emergency shoulders on either side of the roadway are especially problematic. Incorporating enforcement pullout areas into construction phasing plans has been suggested as a way to improve enforcement activities. However, no guidance had been available on how frequently such enforcement areas should be incorporated. Research was conducted to determine law enforcement and contractor opinions on acceptable spacing criteria for pullout areas in a highway work zone. Two sets of surveys were made by using the Delphi method to solicit the opinions of law enforcement officers and roadway contractors regarding the relative difficulty or effectiveness of pullout areas located at various spacings through a long work zone. The Delphi method was used to quickly bring these groups to consensus. Construction contractors generally were against placing pullout areas closer than 2 mi apart. By contrast, law enforcement officers indicated that at spacing greater than 3 mi, the pullout area would not be useful for traffic enforcement. The results indicate that enforcement pullout areas in work zones should be spaced approximately every 2 to 3 mi or, as an alternative, work zones that eliminate emergency shoulders that are adequate for enforcement purposes should be no longer than 3 mi.
Evaluating Speed-Reduction Strategies for Highway Work Zones
Authors: Wang Chunyan , Dixon Karen K. , Jared David
Published: April 2007

Research was conducted to identify the potential of fluorescent orange sheeting, innovative message signs, and changeable message signs with radar for reducing speeds in highway work zones. The study investigated the effect of each strategy immediately after implementation (immediate effect) as well as several weeks after implementation (novelty effect). In addition to the overall effect of each strategy on all vehicles, the study included the effect on specific vehicle types during various lighting conditions. The researchers collected traffic data before, immediately after, and 2 or 3 weeks after implementation of each strategy (3 consecutive weeks for the changeable message sign). They collected data upstream of the temporary traffic-control zone, in the advancewarning area, and adjacent to the active work area. The researchers used various statistical tests to evaluate the significance of speed changes from phase to phase and adjusted vehicle speeds with the upstream speed changes over time. The study indicated that fluorescent orange sheeting and innovative message signs help reduce speeds at highway work zones (with diminished influence over time). Moreover, both strategies influence vehicle speeds more during the day than at night. Drivers of passenger vehicles tended to decrease their speeds more than did truck drivers. Changeable message signs with radar significantly reduced the vehicle speeds in the immediate vicinity of the sign and did not demonstrate a novelty effect.
Relationship Between Winter Road-Surface Conditions and Vehicular Motion: Measurements by Probe Vehicles Equipped with Global Positioning System
Authors: Nakatsuji Takashi , Kawamura Akira
Published: April 2007

A major concern of drivers in winter is the current road condition. Taxis, which move ceaselessly around a wide area, have great potential as sensors for detecting road-surface conditions in a given area. To establish a method with which to estimate road conditions based on the vehicular motion of taxis, field experiments were conducted by using probe vehicles fitted with vehicular-motion sensors and a Global Positioning System device, before implementation in taxis. Preliminary analyses were performed by using data measured on a test track, urban streets, and an expressway. The slip ratio, defined as the relative difference in speed between vehicle and tire wheel, was effective in indicating how slippery the road surfaces were. Taxi vehicular-motion data were collected for more than 1 month, although unlike with probe vehicles, the wheel speed was not measured. Some features of vehicular motion specific to slippery roads were identified, and the discriminability of road conditions, whether icy or dry, without the use of wheel-speed data, was examined.
Nighttime Visibility and Retroreflectance of Pavement Markings in Dry, Wet, and Rainy Conditions
Authors: Schnell Thomas , Aktan Fuat , Lee Yi-Ching
Published: April 2007

Research was conducted to determine the nighttime visibility of flat pavement-marking tape, patterned pavement-marking tape, and wetweather pavement-marking tape in dry, wet (just after rainfall), and simulated rain conditions (ongoing 1-in./h rainfall). The measures of effectiveness were the detection distances, the eye-fixation distributions, and the pavement-marking retroreflectance. The research was sponsored by FHWA. The experiment was conducted on a test track in Cottage Grove, Minnesota. This test track had a section at which 1-in./h rainfall could be simulated. Eleven women and seven men, ranging in age from 55 to 74 (average age 62.5), participated in this study. The participants drove the experiment vehicles along the pavement-marking treatments. The participants were to state the earliest point at which they could see the end of the pavement markings. The retroreflectance of each pavement-marking material was measured with three handheld retroreflectometers under the three weather conditions according to ASTM E-1710 (dry), ASTM E-2177 (wet recovery), and ASTM E-2176 (continuous wetting). The retroreflectance values were correlated to the detection distances to determine the ability of each ASTM test method to predict visibility performance under the corresponding weather condition. The wet-weather tape performed best for detection distance, followed by the patterned tape and the flat tape. The detection distances were longest in the dry condition, shorter in the wet condition, and shortest in the simulated rain condition.
Evaluation of Rail Passenger Equipment Crashworthiness Strategies
Authors: Tyrell David , Perlman A. Benjamin
Published: April 2007

Comparisons are made of the effectiveness of competing crashworthiness strategies—crash energy management (CEM) and conventional passenger train design. CEM is a strategy for providing rail equipment crashworthiness that uses crush zones at the ends of cars. These zones are designed to collapse in a controlled way during a collision, distributing the crush among the train cars. This technique preserves the occupied spaces in the train and limits the decelerations of the occupant volumes. Two scenarios are used to evaluate the effectiveness of the crashworthiness strategies—( a) a train-to-train collision of a cab-car–led passenger train with a standing locomotive–led passenger train and ( b) a grade-crossing collision of a cab-car-led passenger train with a standing highway vehicle. The maximum speed for which all the occupants are expected to survive and the predicted increase in fatalities and injuries with increasing collision speed are determined for both train designs. Crash energy management is shown to significantly increase the maximum speed at which all the occupants could survive for both grade crossing and train-to-train collisions for cab-car–led trains, at the expense of modestly increasing the speeds at which occupants impact the interior in train-to-train collisions.
Experience with the Precast Span Method on the Korean High-Speed Rail Project
Authors: Dong Kang Kee , Suh Sunduck D.
Published: April 2007

The Korean High-Speed Rail Project, Korean Train Express, has 109 km (67 mi) of bridges that comprise about 27% of the entire alignment. The successful construction of these bridges significantly affects overall project progress. To meet tight schedule and quality control standards, in addition to cost savings, contractors proposed the precast span method (PSM) versus the original girder designs on some segments of the line. This first application of PSM to high-speed rail in Korea has posed some challenges: design requirements for high-speed railway bridges are stricter than those for road bridges because of stringent deformation requirements. The adoption of PSM girders has improved the construction quality and schedule. PSM requires no falsework and is not limited by ground and weather conditions, thus being well suited for the construction of long viaducts under stringent budget and construction schedule requirements. With PSM, one full span of a precast-concrete box girder is manufactured in a casting yard, lifted by hydraulic jacks, transported with a special carrier, and placed by the launching girder into the final position. The PSM units are then tied into two or three 25-m (82-ft) or continuous spans using cast-in-place concrete in place of concrete and posttensioning. The contractors manufactured the PSM girders in a temporary manufacturing facility and reduced the installation cycle time for one 25-m (82-ft) long box girder to 11/2 days. The design, fabrication, transportation, and installation of the box girders for the Korean high-speed railway viaducts with PSM are discussed. Project and economic implications of PSM are compared with the movable scaffolding system method.
Heavy Axle Load Effects on Fatigue Life of Steel Bridges
Authors: Unsworth John F.
Published: April 2007

Heavy axle railway loads (freight equipment with more than a 100-ton capacity and gross vehicle weights exceeding 263,000 lb) have been introduced extensively on North American Class I freight railroads in the past decade. An overview is presented of the effects of heavy axle loads on the fatigue life of steel bridges in the North American freight railroad infrastructure. Also outlined are life extension and rehabilitation techniques typically used to maintain the safety and reliability of existing steel railway bridges.
Multivariate Statistical Model for Predicting Occurrence and Location of Broken Rails
Authors: Dick C. Tyler , Barkan Christopher P. L. , Chapman Edward R. , Stehly Mark P.
Published: April 2007

Broken rails are the leading cause of major accidents on U.S. railroads and frequently cause delays. A multivariate statistical model was developed to improve the prediction of broken-rail incidences (i.e., service failures). Improving the prediction of conditions that cause broken rails can assist railroads in allocating inspection, detection, and preventive resources more efficiently, to enhance safety, reduce the risk of hazardous materials transportation, improve service quality, and maximize rail assets. The service failure prediction model (SFPM) uses a combination of engineering and traffic data commonly recorded by major railroads. A Burlington Northern Santa Fe Railway database was developed in which the locations of approximately 1,800 service failures over 2 years were recorded. The data on each location were supplemented with information on other engineering and traffic volume parameters. A complementary database with the same parameters was developed for a randomly selected set of locations at which service failures had not occurred. The combined databases were analyzed using multivariate statistical methods to identify the variables and their combinations most strongly correlated with service failures. SFPM accuracy in predicting service failures at specific locations exceeded 85%. Although further validation is necessary, SFPM is promising in the quantitative prediction of broken rails, thereby improving a railroad’s ability to manage its assets and risks.
Vehicle Reidentification as Method for Deriving Travel Time and Travel Time Distributions: Investigation
Authors: Sun Carlos , Arr Glenn , Ramachandran Ravi P.
Published: April 2007

Vehicle reidentification was investigated as a method for deriving travel time and travel time distributions with loop and video detectors. Vehicle reidentification is the process of tracking vehicles anonymously from site to site to produce individual vehicle travel times and overall travel time distribution. Travel time and travel time distribution are measures of the performance and reliability of the transportation system and are useful in many transportation applications such as planning, operations, and control. Findings from the investigation included ( a) results from a platoon reidentification algorithm that improved upon a previous indvidual vehicle reidentification algorithm, ( b) sensitivity analysis on the effect of time windows in deriving travel times, and ( c) derivation and goodness of fit of travel time distributions using vehicle reidentification. Arterial data from Southern California were used in testing the algorithm’s performance. Test results showed that the algorithm can reidentify vehicles with an accuracy of greater than 95.9% with 92.4% of total vehicles; can calculate individual travel times with approximately 1% mean error with the most effective time window; and can derive travel time distributions that fit actual distributions at a 99% confidence level.
Ultrasonic C-Scan Imaging: Preliminary Evaluation for Corrosion and Void Detection in Posttensioned Tendons
Authors: Iyer Shivprakash , Schokker Andrea J. , Sinha Sunil K.
Published: April 2007

Corrosion of the nation’s transportation infrastructure is a widespread and costly problem. The most prevalent durability issue in reinforced concrete structures is chloride-induced corrosion of the reinforcing steel. A reliable method of determining grout voids and corrosion levels in posttensioned bridge structures is needed. Traditional techniques of corrosion monitoring (e.g., half-cell potential and corrosion rate measurement) are problematic when used in this type of structure, as are standard nondestructive evaluation (NDE) methods, such as impact echo. C-scan imaging, an ultrasonic technique used primarily in the composites industry for detecting delamination, is examined as a method of evaluating grouted posttensioned tendons. This method exhibits many promising qualities: it can be used for internal or external tendons and on metal or plastic ducts; access to only one side of a specimen is required; strong imaging allows easy interpretation of results; the technique poses no risk to users or the environment; and the method has strong potential for development as a handheld field tool. The C-scan technique may be valuable for the investigation of not only posttensioning applications but other types of reinforced concrete structures as well. Results of preliminary investigations on lab specimens indicate that the C-scan technique holds promise. The ultimate goal of the research is to provide a user-friendly, robust system for the NDE of posttensioned tendons for voids, corrosion, and wire breaks. Recommendations for optimal acquisition and processing techniques as well as for the future development of the equipment as a field tool are proposed.
Evaluation of Pedestrian Data Needs and Collection Efforts
Authors: Cottrell Wayne D. , Pal Dharminder
Published: April 2007

Research was done to evaluate the extent to which the pedestrian data collection efforts of transportation agencies in the United States are addressing pedestrian safety factors. There was also consideration of how pedestrian data collection can be improved to facilitate the monitoring of these factors. Fifteen pedestrian safety issues are identified based on a literature review and examination of pedestrian–vehicle crashes in Utah. A 2001 survey of U.S. transportation agencies indicated that 45 (75%) of the 60 respondents were counting pedestrians at various locations. Hand counting, the recording of push-button use, and video cameras were methods used to collect data. Automated systems, such as position sensors and image processing, were not used to count pedestrians. The use of advanced data collection technologies is not critical to the resolution of pedestrian safety concerns, although permanent counting installations might increase data collection efficiency. Only 4 of the 15 pedestrian safety issues were specifically being addressed by the agencies’ data collection efforts. Their existing methods could, however, be used to target seven additional safety factors. The development of a pedestrian data monitoring guide is recommended; an outline is proposed. Several agencies admitted that pedestrian volumes did not affect their pedestrian treatments. Evidently, some transportation agencies could benefit from direction on how to relate pedestrian demand and behavior data to safety improvements.
Experimental Research of Pedestrian Walking Behavior
Authors: Daamen Winnie , Hoogendoorn Serge P.
Published: April 2007

To assess the design of walking infrastructure—such as transfer stations, shopping malls, sport stadiums, and others, as well as to support planning of timetables for public transit—tools to aid the designer are needed. To this end, microscopic and macroscopic pedestrian flow models can be and have been applied. To calibrate and validate such models, as well as to gain more insight into the characteristics of pedestrian flows under a variety of circumstances, detailed pedestrian flow data are required. Delft University of Technology has recently carried out experimental research of pedestrian flow. Described is the experimental design (such as determination of process variables and measurement), the resulting microscopic pedestrian data, and some initial results for the narrow bottleneck experiment. Both microscopic and macroscopic characteristics of the pedestrian flows are presented. Interesting first results pertain to the way in which the narrow bottleneck is used under saturated flow conditions, and the use of the space (or, rather, width) upstream of the bottleneck in case of congestion.
Pedestrian Safety Through a Raised Median and Redesigned Intersections
Authors: King Michael R. , Carnegie Jon A. , Ewing Reid
Published: April 2007

Documentation was done on the effect of a raised median, signalized and redesigned intersections, curbs, and sidewalks on vehicle speed, pedestrian exposure risk, driver predictability, and vehicle volume along a four-lane suburban roadway in central New Jersey. The analysis used both quantitative tools (speed and volume counts, timing runs) and qualitative methods (pedestrian tracking, video, before-and-after photography). The results are that the 85th-percentile vehicle speed fell by 2 mi/h and pedestrian exposure risk decreased by 28%. Also, the median allows pedestrians to cross one direction of traffic at a time and signals, curbs, median, redesigned intersections, and striping patterns work together to manage driver behavior. In regard to vehicles, it was found that vehicle volumes were not affected and that vehicle speeds acted independently of vehicle volumes. A collision analysis projected a savings of $1.7 million over the next 3 years in direct and indirect costs. The goal of the report was to produce a simple and straightforward analysis tool for similar projects in the area. Some of the benefits of roadway projects such as these can be quantified numerically, whereas others rely on qualitative analyses. For example, before-and-after speeds are easily gathered and compared, whereas before-and-after pedestrian behavior at the raised median requires a more in-depth approach made easier by digital cameras. Together, before-and-after data and before-and-after imaging present a more holistic picture of the benefits and limitations of a project.
Methodology for Evaluating the Safety of Midblock Pedestrian Crossings
Authors: Cui Zhenzhong , Nambisan Shashi S.
Published: April 2007

Spatial and temporal characteristics of midblock pedestrian crashes (MBPCs) were evaluated toward a better understanding of where and when the MBPCs occur. Existing databases related to traffic crashes were used. Other data used include traffic and geometric characteristics of the roadways under consideration as well as analyses of pedestrian and driver behaviors. General statistical analysis methods were used to evaluate various hypotheses. The statistical Z-test was used to evaluate the age and gender distribution, light condition, fatalities, and alcohol- or drug-use–related characteristics involved in MBPCs. The results correlated these factors with the potential for the occurrence of MBPCs. The Wilcoxon Signed Rank test was used as a nonparametric test to compare the safety of midblock crossings with the safety of crossings at intersections. The methodology was tested and validated using midblock locations in the Las Vegas metropolitan area. The results indicate that there is a significantly lower potential for conflict if pedestrians cross at an intersection instead of crossing at a midblock location. Although this methodology was applied to data from the Las Vegas metropolitan area, it is applicable to evaluating the safety of MBPC anywhere else, provided that appropriate data are available.
Effect of Styrene Butadiene Styrene Modifier on Cracking Resistance of Asphalt Mixture
Authors: Kim Booil , Roque Reynaldo , Birgisson Bjorn
Published: April 2007

A laboratory investigation was conducted to evaluate the effects of styrene butadiene styrene (SBS) modification on the cracking resistance and healing characteristics of coarse-graded Superpave® mixtures. Four types of asphalt mixtures with 6.1% and 7.2% design asphalt contents using unmodified and SBS-modified asphalt cement were produced in the laboratory. Tests performed with the Superpave indirect tensile (IDT) test included repeated-load fracture and healing test, strength tests at two loading rates, and longer-term creep tests to failure. The test results showed that the benefit of SBS modifiers to mixture cracking resistance appeared to be primarily derived from a reduced rate of micro-damage accumulation. The reduced rate of damage accumulation was reflected in a lower m value without a reduction in fracture limit or healing rates. It was shown that the benefits of the SBS modifier were clearly identified by using the hot-mix asphalt fracture model, which accounts for the combined effects of m value and fracture energy limit on cracking resistance. It was also determined that the residual dissipated energy as determined from Superpave IDT strength tests appears to be uniquely associated with the presence and benefit of SBS modification and may provide a quick way to make relative comparisons of cracking performance. Longer-term creep test showed that time to crack initiation appeared to provide another parameter uniquely related to the effects of SBS modification. The key to characterizing the effects of SBS modifier on the cracking resistance of asphalt mixture is in the evaluation of the combined effects of creep and failure limits.
Analytical Formulas for Film Thickness in Compacted Asphalt Mixture
Authors: Radovskiy Boris
Published: April 2007

Recently, several researchers have proposed asphalt film thickness as a criterion for ensuring the durability of asphalt mixtures. However, they suggested that the standard film thickness equation, which dates back to the 1940s, needs to be examined by modern technology and improved. A presumable background on which the Asphalt Institute surface area factors are based was recovered and analyzed in detail. A fundamentally sound model for film thickness calculation was developed using a model of asphalt concrete in which the aggregates are spherical but have an arbitrary size distribution. A recent result from statistical geometry is applied to determine the film thickness for any volume fraction of aggregates and any volume fraction of effective asphalt. The analytical formulas are presented, the details of the calculation are summarized, and examples are provided.
Click It or Ticket: Boosting Seat Belt Use in Hawaii
Authors: Kim Karl , Yamashita Eric
Published: April 2007

In compliance with its mandatory seat belt law, Hawaii is a high-use state. Seat belt use from 1998 to 2001 has averaged 81%, compared with 70% nationally. Efforts to increase belt use beyond 90% have not been successful, at least until the most recent effort, which entailed a combined enforcement and public information campaign. Described are patterns of belt use over time and the effects of the "Click It or Ticket" campaign that was launched this year. In January 2002, before the program was started, there was an overall belt use rate of 83.5%. After increased enforcement and publicity, Hawaii experienced an immediate increase in belt use by 6.9%. Belt use increased dramatically in each of the state’s four counties: in Honolulu, a 7.5% increase; Maui, 10.1% increase; and Kauai, 5% increase. The county of Hawaii, however, increased its rate by only 2.7%. Additional surveys in the months following the campaign indicated that in the days and weeks immediately after the Click It or Ticket campaign, there was a significant drop-off in belt use; but 144 days after, belt use in Honolulu County has stabilized at above 90%. This is surprising because the actual observed current rate is higher than the rate projected on the basis of observations conducted during the weeks immediately after the campaign was initiated. While more surveys and analysis are planned, the campaign was successful in Hawaii. Comments are provided about increasing belt use in a high-use state and implications are described for other traffic safety programs and initiatives.
Effects of Speed Limit Enforcement Cameras on Accident Rates
Authors: Hess Stephane , Polak John
Published: April 2007

Speed limit enforcement cameras (SLECs) have been in operation in Great Britain since 1991. However, there is still considerable dispute regarding their effectiveness in reducing accident rates. The aim of this research was to analyze the effects of SLECs on accident rates in Cambridgeshire, United Kingdom, using time series data collected over an 11-year period. A time series analysis of the accident data revealed the presence of both trend and seasonality components. A method was developed to remove the influence of these two components from the data and compare mean accident levels before and after installation of the camera. The method was also constructed in such a way that it would be able to distinguish between the actual effects of the camera installation and the effects of regression to the mean. The initial investigation into the effects of SLECs showed an average decrease over sites in the monthly accident frequency by around 18%; a more detailed analysis suggested that the best approximation of the effect of the introduction of a SLEC is a decrease in injury accidents by 31.26%, thus giving clear evidence that SLECs do indeed contribute to a significant decrease in accident numbers.
Evaluation of Speed Camera Enforcement in the District of Columbia
Authors: Retting Richard A. , Farmer Charles M.
Published: April 2007

Washington, D.C., implemented a speed camera enforcement program in 2001. Vehicle speeds were measured before and after the program. Seven sites in Washington were selected randomly from a total of 60 targeted enforcement zones. Speed data were collected 1 year before enforcement and approximately 6 months after enforcement began. Results indicated that mean traffic speeds and the proportion of drivers traveling more than 10 mph above the speed limit—fast enough to warrant a speeding ticket—were reduced at each of the Washington study sites. At eight comparison sites in nearby Baltimore, Maryland, where speed camera enforcement was not in place, no decline in traffic speeds was observed. Overall, mean speeds at Washington sites declined by a statistically significant 14% compared with Baltimore sites, and the proportion of vehicles exceeding the speed limit by more than 10 mph declined 82%. These findings indicate that speed camera enforcement reduced speeding on surface streets throughout Washington. On the basis of prior research, such speed reductions can be expected to reduce the frequency and severity of motor vehicle crashes.
Legislative Issues Related to Automated Enforcement of Red-Light Running
Authors: Kraus Edgar , Quiroga Cesar
Published: April 2007

Red-light running is one of the leading causes of crashes in urban areas in the United States. A number of strategies are available to address this problem, including engineering countermeasures, educational campaigns, and improved law enforcement. Law enforcement agencies are increasingly relying on automated systems using photographic devices to enforce red-light-running laws. While automated enforcement systems appear to have wide public support, there is considerable confusion among drivers, engineers, planners, and decision makers as to the legality and constitutionality of those systems. The debate is particularly acute when it comes to issues such as privacy, use of information, and constitutional rights. These issues are analyzed and legal strategies are compared in states that have passed or attempted to pass legislation to regulate automated enforcement. The analysis highlights differences among states depending on their statutory laws and whether red-light violations are treated as civil or criminal offenses. The analysis reveals major differences in the way states legislate program details, which, in turn, affect program implementation. Also included is a review of current European red-light-running legislation, where automated enforcement systems have a longer history than in the United States.
Continuous Time Representation and Modeling Framework for Analysis of Nonworker Activity-Travel Patterns: Tour and Episode Attributes
Authors: Misra Rajul , Bhat Chandra R. , Srinivasan Sivaramakrishnan
Published: April 2007

A set of four econometric models is presented to examine the tour and episode-related attributes (specifically, mode choice, activity duration, travel times, and location choice) of the activity-travel patterns of non-workers, as a sequel to an earlier work by Bhat and Misra (2001), which presented a comprehensive continuous-time framework for representation and analysis of the activity-travel choices of nonworkers. Detailed descriptions of the first two components of the modeling framework related to the number and sequence of activity episodes are also presented. The proposed models using activity-travel data from the 1990 San Francisco Bay Area travel diary survey are estimated.
Combined Modal Split and Stochastic Assignment Model for Congested Networks with Motorized and Nonmotorized Transport Modes
Authors: Wu Z. X. , Lam William H. K.
Published: April 2007

A network equilibrium model is proposed for the simultaneous prediction of mode choice and route choice in congested networks with motorized and nonmotorized transport modes. In Hong Kong, motorized and nonmotorized modes are competing travel alternatives, as the average trip length is relatively short because of high-density development in urban areas. In addition, nonmotorized modes such as walking usually serve as complements to motorized trips. For example, transit passengers have to walk to gain access to and egress from transit stops. Here, the transit and walking modes are representatives of motorized and nonmotorized transport modes, respectively. The fundamental congestion effects of each mode and intermodal interactions are taken into account in the simultaneous mode and route choice problem. An equivalent variational inequality (VI) problem is formulated to capture all the components of the proposed model in an integrated framework. A solution algorithm is presented for solving the VI problem. A numerical example is used to illustrate the application of the proposed model and solution algorithm. More refined estimates of travel times and network flows can be obtained with the proposed model.
Measuring Sprawl and Its Transportation Impacts
Authors: Ewing Reid , Pendall Rolf , Chen Don
Published: April 2007

Across the United States, urban sprawl, its impacts, and appropriate containment policies have become the most hotly debated issues in urban planning. Today’s debates have no anchoring definition of sprawl, which has contributed to their unfocused, dogmatic quality. Efforts to measure sprawl and test for relationships between sprawl and transportation outcomes are described. This is the first use of the newly minted Rutgers–Cornell sprawl indicators. Sprawl is operationalized by combining many variables into a few factors representing density, land use mix, degree of centering, and street accessibility. This consolidation of variables is accomplished with principal component analysis. These factors are then related to vehicle ownership, commute mode choice, commute time, vehicle miles traveled per capita, traffic delay per capita, traffic fatalities per capita, and 8-h ozone level. These associations are made with multiple regression analysis. For most travel and transportation outcomes, sprawling regions perform less well than compact ones. The exceptions are average commute time and annual traffic delay per capita, which do not clearly favor compactness over sprawl. The main limitation of this study has to do with the data it uses. By necessity, the study uses highly aggregate data from a variety of sources that are not always consistent as to the area under study and time period. They are simply the best data available from national sources with sufficient breadth to provide a panoramic view of sprawl in the United States. Results will have to be validated through follow-up work of a more focused nature.