bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability Analysis of Cracking and Faulting Prediction in the New Mechanistic–Empirical Pavement Design Procedure
Authors: Darter Michael , Khazanovich Lev , Yu Tom , Mallela Jag
Published: May 2018

Reliability analysis is an important part of the mechanistic–empirical pavement design guide (M-E PDG). Even though mechanistic concepts provide a more accurate and realistic methodology for pavement design, a practical method to consider the uncertainties and variations in design and construction is needed so that a new or rehabilitated pavement can be designed for a desired level of reliability (performance as designed). Several methods, ranging from closed-form approaches to simulation-based methods, can be adopted to perform reliability-based design. However, some methods may be more suitable than others, given the complexities of the design procedure. A formal definition of reliability within the context of the M-E PDG, as well as two reliability analysis approaches considered for incorporation into the design procedure for evaluating the reliability of the rigid pavement design for cracking and faulting, was evaluated. A Monte Carlo–based simulation was combined with the damage accumulation procedure for rigid pavement distress prediction. This approach is recommended for future improvements of the procedure. The development of the reliability analysis procedure implemented into the M-E PDG also was documented. It was demonstrated that although the adopted approach is not as sophisticated as a Monte Carlo–based one, it still represents a step forward compared with AASHTO-93 reliability analysis.
Improving Effectiveness and Reliability in Geotechnical Investigations with a Personal Digital Assistant
Authors: Feng Zhengyi , Wang Tian-yu , Lin Der-guey , Chern Jin-ching
Published: May 2018

Personal digital assistant (PDA) applications to improve the effectiveness and reliability in geotechnical investigations have been developed. Because of PDA's legerity and mobility, it is an excellent choice for use with a simple global position system (GPS) in geotechnical field work, such as site reconnaissance, subsurface investigation, surface investigation, safety evaluation, testing, and instrumentation. Using PDAs in geotechnical engineering can save traditional field paper forms, avoid repeated record input, reduce the risk of wrong data interpretation, and shorten the time and space “barrier” between the office and the field. After the field data are collected on the PDA, they can be transferred to a desktop personal computer (PC) for further processing and reporting. The desktop PC is designated to handle more complicated analyses and visual presentations. Specialized functions of applications to operate PDA and GPS, as well as for the desktop PC, were developed according to the characteristics of the geotechnical tasks. The concept and framework were applied for three geotechnical assistant systems: drilling investigation assistant system, surface geologic investigation assistant system, and slope safety evaluation assistant system. In addition, an example illustrates the application of GPS, PDA, and geographic information systems for debris flow reconnaissance. Using PDAs improves the effectiveness and reliability of geotechnical investigations and is promising for further development.
Real-Time Compaction Monitoring in Cohesive Soils from Machine Response
Authors: White David J. , Jaselskis Edward J. , Schaefer Vernon R. , Cackler E. Thomas
Published: May 2018

Recent developments for measurement and analysis of machine power response caused by changes in physical soil properties have the potential to change completely the future of earthwork construction. A technique in which a self-propelled sheepsfoot roller was used to compact cohesive soils was developed; field pilot studies were then conducted. Results from field tests using conventional testing techniques (nuclear moisture–density gauge, dynamic cone penetrometer, drive core, and Clegg impact hammer) showed strong correlations to machine power ( r2 > 0.9) when data were averaged over a 20-m test strip. These developments related to measurement and analysis of machine energy as a function of changes in physical soil properties and provide the benefit of 100% coverage combined with a differential Global Positioning System and ruggidized touchscreen computer monitor showing spatial information on cumulative number of passes and machine power output. Results can be transmitted in real time to an on-site computer for review via a wireless Internet system.
Design of Ribbed Concrete Approach Slab Based on Interaction with the Embankment
Authors: Shi X. M. , Cai C. S. , Voyiadjis George , Zhang Zhongjie
Published: May 2018

To alleviate the “bump” problem at bridge ends, a ribbed concrete approach slab (similar to slab-on-beam bridge decks) was proposed in place of the pile–column-supported approach span or flat slab system. The effect of given embankment settlement on the structural performance of a ribbed concrete approach slab with a span length of 60 ft and a width of 40 ft was investigated. The approach slab was modeled as a ribbed slab with a beam spacing of 32, 16, and 12 ft. A three-dimensional finite element analysis was conducted to model the interaction between the approach slab and the embankment soil. Finite element modeling techniques that simulate the separation of the slab and soil provide information on the effect of the embankment settlement on structural performance and beam design. The predicted internal forces provide design engineers with a scientific basis to design the approach slab properly, considering different levels of embankment settlements. Current AASHTO code specifications do not provide guidelines to design approach slabs considering the embankment settlement.
Development and Application of a Rut Prediction Model for Flexible Pavement
Authors: Tarefder Rafiqul Alam , White Luther , Zaman Musharraf
Published: May 2018

A four-layer neural network (NN) was constructed and applied to determine mapping associating factors in the design and testing of asphalt samples with their performance in repetitive rutting tests. A total of 1,586 samples (two samples per data point) were tested to determine rutting with the use of an asphalt pavement analyzer. Test results and mix volumetric properties were used to train the NN model. Preprocessing and principal component analysis were used, and the network was trained with the Levenberg–Marquardt algorithm. With randomly generated weighting factors to initialize the training algorithm, histograms were compiled, and outputs were estimated. Excellent agreement was observed between simulations and test data. The developed NN was used to estimate the optimum asphalt content of a Superpave® mix, and the results were satisfactory. The developed NN model will be a useful tool in the study of asphalt construction and wear.
Performance of an Induced Trench Installation
Authors: McAffee Rodney P. , Valsangkar Arun J.
Published: May 2018

An induced trench installation was instrumented to measure earth pressures both within the embankment and on the pipe. Deformations of the pipe and settlements within the embankment also were monitored. At the full height of the embankment, the average vertical and horizontal stress on the culvert remained relatively constant at 0.32 and 0.48 times the overburden stress, respectively. The pressures measured directly on the pipe compare favorably with other case histories presented within the literature and are in good agreement with the observed vertical elongation of the culvert. Pressure cells positioned within the embankment measured stresses roughly equal to the overburden stresses and indicate no significant redistribution of stresses other than those observed immediately around the pipe. The relative settlements within the embankment, above the induced trench installation, correspond with the design assumption that the fill within the prism of soil over the pipe settles downward relative to the adjacent fill. However, the recommended settlement ratio parameter used in the analysis, on the basis of geometry alone, may be questionable. That higher-than-expected lateral stresses on the pipe need to be considered in design was confirmed. Marston's formula and lower-bound input parameters appear to give a conservative estimate of the vertical loads on buried pipes.
Potential Crash Involvement of Young Novice Drivers with Previous Crash and Citation Records
Authors: Chandraratna Susantha , Stamatiadis Nikiforos , Stromberg Arnold
Published: May 2018

A goal for any licensing agency is the ability to identify crash-prone drivers. Thus, the objective of this study is the development of a crash prediction model that can be used to estimate the likelihood of a young novice driver's involvement in a crash occurrence. Multiple logistic regression techniques were employed with available Kentucky data. This study considers as crash predictors the driver's total number of previous crashes, citations accumulated, and demographic factors. The driver's total number of previous crashes was further disaggregated into the driver's total number of previous at-fault and not-at-fault crashes. Sensitivity analysis was used to select an optimal cut-point for the model. The overall efficiency of the model is 77.82%, and it can be used to classify correctly more than one-third of potential crash-prone drivers if a cut-point of 0.247 is selected. The total number of previous at-fault and not-at-fault crash involvements and the accumulation of speeding citations are strongly associated with a driver's being at risk. In addition, a driver's risk is increased by being young and being male. Although the statistical nature of driver crash involvements makes them difficult to predict accurately, the model presented here enables agencies to identify correctly 49.4% of crash-involved drivers from the top 500 high-risk drivers. Moreover, the model can be used for driver control programs aimed at road crash prevention that may range from issuance of warning letters to license suspension.
Classifying Passing Maneuvers
Authors: Jenkins J. M. , Rilett L. R.
Published: May 2018

Passing an impeding vehicle on a two-way two-lane roadway is a complex maneuver because of the variety of passing conditions and driver behavior. In this study, the supposition that passing maneuvers can be classified on the basis of a quantitative description of passing behavior was examined by analyzing data collected during a passing experiment conducted in a driving simulator. Evidence was found to support the following hypotheses: ( a) the speed increase of the passing vehicle during the passing maneuver is smaller when the speed difference between the passing and impeding vehicles at the moment of initial acceleration is greater and ( b) the speed reduction of the passing vehicle during the latter portion of the passing maneuver is greater when the time to collision with the oncoming vehicle at the moment when the passing vehicle returns to the right lane is greater. Therefore, it was concluded that the start of a pass can be classified by acceleration behavior, and the end of the pass can be classified by deceleration behavior. This behavioral approach is an improvement to classifying passing maneuvers on the basis of a qualitative assessment of the passing conditions, as in establishing the AASHTO passing sight distance design criteria and the minimum passing sight distances in the Manual on Uniform Traffic Control Devices for Streets and Highways. A particular passing behavior, described by a specific acceleration and deceleration behavior, could be used to modify or update these criteria, thereby improving the guidance given to passing drivers and potentially the safety of passing areas.
Visual Sampling of In-Vehicle Text Messages
Authors: Hoffman Joshua D. , Lee John D. , McGehee Daniel V. , Macias Mashala , Gellatly Andrew W.
Published: May 2018

Emerging in-vehicle technology associated with radio data systems, satellite radio, navigation aids, and infotainment systems will expose drivers to an increasing amount of textual information. The visual demands of driving make it critically important to understand how characteristics of such information affect visual sampling of the roadway. This study used a medium-fidelity driving simulator to evaluate the effect of scroll control (manual or automatic), the number of lines displayed (one, two, or four), and scrolling strategy (line by line or page by page) on drivers’ visual sampling behavior of text messages. Fifteen men and 15 women aged 25 to 51 (mean 35.7, s.d. 7.5) participated. Consistent with previous models of sampling behavior, text message characteristics affected the number of glances much more strongly than the duration of glances, and drivers were able to protect driving performance even with a demanding secondary visual task. However, the number of lines of text displayed increased the mean glance duration, the variability of glance duration, and the number of glances greater than 2 s. Scrolling text line by line increased visual demand relative to scrolling page by page, particularly when scrolling is manually controlled by the driver. Manual control of scrolling by using a touch screen button led to greater visual demand compared with automatically scrolled text.
Eye Glance Behavior of van and Passenger Car Drivers during Lane Change Decision Phase
Authors: Tijerina Louis , Garrott W. Riley , Stoltzfus Duane , Parmer Edwin
Published: May 2018

Data are presented on the eye glance behavior of passenger car and van drivers before the start of discretionary lane changes. Thirty-nine volunteers ranging from 20 to 60 years of age served as either van drivers (N = 19) or passenger car drivers (N = 20) in the study. Each driver used an instrumented vehicle and was accompanied by a ride-along observer in daylight and dry pavement conditions. The test route included driving on both public highways at 55 mph or more and city roads at 25 to 35 mph. A total of 549 lane changes (290 for vans, 259 for passenger cars) were analyzed in terms of driver eye glance behavior 10 s before the lane change start. Results indicated that for left-to-right lane changes, the probability of a glance to the center mirror was substantially higher than the probability of a glance to the right side mirror. For right-to-left lane changes, the probability of a glance to the center mirror was substantially less than that for rightward lane changes, and the probability of a glance to the left side mirror was appreciably higher than that for right side mirror use in rightward lane changes. These results held for both van and passenger car drivers. Except for a slightly higher probability of over-the-shoulder glances on city roads, these results hold for both highway and city street driving. These data should be factored into the design of lane change warning system displays and mirror systems.
Eye Glance Behavior during Lane Changes and Straight-Ahead Driving
Authors: Olsen Erik C. B. , Lee Suzanne E. , Wierwille Walter W.
Published: May 2018

Understanding drivers’ eye behavior before lane changing is an important aspect of designing usable, safe lane-change collision-avoidance systems (LCAS) that will fit well with drivers’ expectations. This understanding could lead to improvements for LCAS as well as for a variety of other collision avoidance systems. Findings regarding driver eye glance behaviors are presented in a comparison of lane change maneuvers with straight-ahead (baseline) driving events. Specific eye glance patterns before lane change initiation were observed. When preparing to make a lane change to the left as compared with driving straight ahead, drivers doubled the number of glances toward the rearview mirror and were much more likely to look at other locations associated with moving to the left, including the left mirror and blind spot. On the basis of the eye glance patterns observed and previous results, the following recommendations are made: ( a) visual presence detection indicator displays should be used to provide information about vehicles in the rear adjacent lane any time a vehicle is detected, ( b) a presence indicator should be presented in a visual format, and ( c) the left mirror and rearview mirror locations should be considered for providing lane change information to the driver. The process of acquiring and analyzing eye glance movements is well worth the investment in resources. However, prototype systems must be tested before implementation, and the exact location and format of warning systems warrant a separate research and development effort to ensure safety and reliability.
Methodology for Capturing Driver Eye Glance Behavior during In-Vehicle Secondary Tasks
Authors: Smith David L. , Chang James , Glassco Richard , Foley James , Cohen Daniel
Published: May 2018

Driving is a visual task; any driver behavior that takes the driver's visual attention from the driving environment is likely to increase the risk of a crash. Many new intelligent transportation systems telematics applications are now being installed in cars, and some of these may result in substantial degradation of visual attention. Accurately capturing driver eye glance behavior during the evaluation of these devices is critical to assessing the safety impact of engaging in secondary tasks while driving. The development of a methodology is reported; it reliably determines on-road and off-road eye glance duration by using video data collected during highway driving evaluation trials while drivers were engaged with secondary tasks. Human raters determined glance location and duration by detailed coding of the driver's eye movements on the videos. The raters agreed most of the time, but sufficient disagreement suggested that using the consensus of multiple raters significantly improved the reliability of the resulting eye glance data.
Assessing Multifunction Interfaces in Vehicles
Authors: Burns Peter C. , Trbovich Patricia L. , Harbluk Joanne L. , McCurdie Tara
Published: May 2018

The goal of this research was to determine whether system usability is requisite for system safety. To this end, the usability and safety of two multifunction in-vehicle interfaces were assessed to verify the hypothesis that the system scoring highest on usability testing would also score highest on safety testing. Two multifunctional systems were subjected to ( a) heuristic evaluations to assess usability and ( b) occlusion tests to assess safety. There were more heuristic violations, indicative of more usability problems, in System B relative to System A. Similarly, with regard to safety, results of occlusion testing showed that greater demands on time and visual resources were required to perform tasks when System B was used versus System A. Thus, the usability problems identified through heuristic evaluations represent possible precursors to the safety problems identified by occlusion tests. Given the latter and the fact that heuristic evaluations can be applied quickly and easily whereas occlusion testing can be costly and time-consuming, the results of the current research suggest that developers would benefit from correcting the usability limitations of a system before its safety performance is evaluated.
Use of Fuzzy Sets to Evaluate Driver Perception of Variable Message Signs
Authors: Lee Dongmin , Pietrucha Martin T. , Sinha Sunil K.
Published: May 2018

Current methods for evaluating the quality of service provided by a variable message sign (VMS) may not yield results that represent the satisfaction drivers experience because these techniques cannot represent the variability and complexity of human perception with great fidelity. To solve those problems, a new method that applies fuzzy set theory was developed. Results of a preexisting survey of VMS service quality were reanalyzed with this method. For this application, two membership functions were constructed with two different experimental methods: interval estimation and pairwise comparison. Specifically, construction of the second membership function used Saaty's eigenvector method. These two membership functions employ five linguistic statements to represent the degree of satisfaction and relative importance of six performance criteria. Quality of VMS service perceived by an individual driver was evaluated with the concept of the fuzzy weighted average. A set of 322 quality measures was computed, and they were aggregated and transformed into a single percentage value with the use of an arithmetic fuzzy mean. The defuzzified final value indicates the degree of satisfaction with VMS service perceived by a group of participating drivers, taking into consideration the variance of human perception and the degree of importance of the six criteria. By employing the proposed method, the quality of VMS service as subjectively perceived by humans and influenced by various exogenous factors can be evaluated while still considering the subjective and complicated manner of human thinking.
Normal Deceleration Behavior of Passenger Vehicles at Stop Sign–Controlled Intersections Evaluated with In-Vehicle Global Positioning System Data
Authors: Wang Jun , Dixon Karen K. , Li Hainan , Ogle Jennifer
Published: May 2018

Deceleration characteristics of passenger cars are often used in traffic simulation, vehicle fuel consumption and emissions models, and intersection and deceleration-lane design. Most previous studies collected spot speed data with detectors or radar guns. Because of the limitations of the data collection methods, these studies could not determine when and where drivers began to decelerate. Therefore, the studies may not provide an accurate estimation of deceleration time and distance. Furthermore, most previous studies are based on outdated and limited data, and their conclusions may not be applicable to the current vehicle fleet and drivers. The normal deceleration behavior of current passenger vehicles is evaluated at stop sign–controlled intersections on urban streets on the basis of in-vehicle Global Positioning System data. This study determined that drivers with higher approach speeds decelerated over a longer time and distance. Higher initial deceleration rates were also associated with higher approach speeds. However, the collected data in this study did not indicate a clear relationship between the average and maximum deceleration rates and approach speeds. With second-by-second deceleration profile data, the authors found that most drivers reached their maximum deceleration rates about 5 s or less than 5 s before stopping, and the maximum deceleration rate (3.4 m/s2) recommended by AASHTO was applicable to most of the study drivers. This review verified several previous deceleration models with the current observations and found that the polynomial model developed by Akcelik and Biggs provides the best fit for the data set in this study. Finally, this study developed a new deceleration model based on the approach speeds and deceleration time.
Design for Simulator Performance Evaluations of Driving with Vision Impairments and Visual Aids
Authors: Peli E. , Bowers A. R. , Mandel A. J. , Higgins K. , Goldstein R. B. , Bobrow L.
Published: May 2018

Driving simulator technology provides a safe method for evaluating the impact of vision loss on different components of the driving task and the potential efficacy of visual aids intended to compensate for a particular type of vision loss. Most previous investigations have used general driving scenarios. It is proposed here that scenarios with different task requirements be designed specifically to address the condition under investigation. As an example, the design of driving scenarios and tasks that are specific for the evaluation of one type of visual field loss, homonymous hemianopia, is described. Results of pilot studies show that even with a small sample size, the design is sufficiently sensitive to differentiate individuals with hemianopic visual field loss from control drivers. These results suggest that careful design of test situations, measurements, and analyses provides a strong basis for investigations of driving performance of individuals with specific types of vision impairment and could be used to evaluate the efficacy of low-vision driving aids.
Four-Dimensional Interactive Visualization System for Transportation Management and Traveler Information
Authors: Pack Michael L. , Weisberg Phillip , Bista Sujal
Published: May 2018

This research developed a system for visualizing four-dimensional (4-D), real-time transportation data for the major road networks of Washington, D.C., Northern Virginia, and the entire state of Maryland. The effort employed a combination of OpenGL and other modeling techniques to develop a scalable, highly interactive 4-D model using available geographic information system (GIS) and transportation infrastructure data in conjunction with real-time traffic management center data. The prototype system interacts with real-time traffic databases to show animations of real-time traffic data (volume and speed) along with incident data (accident locations, lane closures, responding agencies, etc.). A user can “fly” or “drive” through the region to inspect conditions at an infinite number of angles and distances. The program also allows users to monitor the status of and interact with traffic control devices such as dynamic message signs, closed-circuit television feeds, and traffic sensors and even view the location of emergency response vehicles equipped with Global Positioning System transceivers. Because the system uses standard GIS data and relatively standard transportation databases to derive traffic measures, it can be scaled to incorporate other states and agencies.
Ensuring the Security of Transportation Facilities
Authors: Nakanishi Yuko J. , Western Jeffrey
Published: May 2018

Advanced vehicle identification technologies can enhance national security and the security of transportation facilities, workers, and customers by preventing unauthorized vehicles from entering a transportation facility, border crossing, or parking area. Manual checks are time-consuming–-license plates must be checked against authorized plates, and the identities of workers and travelers confirmed. Advanced vehicle identification technologies allow faster access for authorized vehicles, reduce the possibility of fraud and error, and permit security personnel to spend more time in evaluating unknown vehicles and persons. This paper discusses several advanced vehicle identification technologies–- automated license plate recognition, vehicle-based identification, and electronic vehicle identification systems–-and their applicability in localized access control and in national security situations. The technologies’ features, costs, accuracy, and feasibility are discussed, and recommendations for further research are provided.
Training in Transportation Security for Hazardous Materials on Motor Carriers
Authors: Lepofsky Mark , Simmons James O. , Beatty Jeffrey K. , Rogers John S.
Published: May 2018

Many credible threats against hazardous materials (hazmat) transportation exist in the United States. This paper outlines the overall regulatory approach to hazmat transportation security by commercial motor carriers in the United States and focuses on the well-received training and outreach efforts that have been put in place to improve the overall level of security in the United States. In the post–September 11, 2001 (9/11), environment, safety-oriented agencies are being asked to accommodate a new role in the security arena. Many regulations affect the highway transportation of hazmat. The Federal Motor Carrier Safety Administration is primarily concerned with the enforcement of safety regulations, and the Research and Special Programs Administration (RSPA) regulates hazmat transportation across all modes. Recently, RSPA implemented new requirements for security assessments and security plans. Because many motor carriers previously did not have much experience with security issues, the guidance provided them is an important element in improving the level of security throughout the industry. The paper discusses how the motor carriers’ security plans are reviewed and assessed by federal and state regulators. A key component of this review process, described in detail, is the importance of providing training to the regulators ( a) to allow them to offer constructive recommendations to improve company security plans and ( b) to develop a consistent approach to enforcement in an environment that is much more subjective than that of the safety-oriented enforcement with which they are familiar.
Securing and Facilitating Trade through U.S. Land Borders
Authors: Ojah Mark
Published: May 2018

A paradigm shift in U.S. policy about inbound commercial shipments has occurred in recent years. Before September 11, 2001, U.S. Customs Services’ regulation of imported goods focused primarily on trade compliance. Since then, Customs’ priority mission has become preventing terrorism against the United States. Two volunteer programs, the Customs Trade Partnership Against Terrorism (C-TPAT) and the Free and Secure Trade (FAST) initiative, were created to reconcile supply chain security and trade facilitation goals. Customs has successfully engaged thousands of companies in trade security by offering benefits such as fewer inspections and expedited border processing. However, this approach is viable only if resources and mechanisms exist to ensure that the shipments being facilitated are indeed more secure. The security practices of current C-TPAT enrollees may not be validated for months or years because of funding and staffing constraints. These limitations also prevent Customs from integrating stakeholders with crucial roles in U.S. trade into C-TPAT and FAST. To improve the ability of these initiatives to safeguard U.S. supply chains, the federal government must increase program funding levels. This will allow more prompt verification of the security of enrollees and expansion of the process to key stakeholders not currently covered under the programs. As technology improves and the number of FAST movements grows, Customs should consider mandating the use of tamper-evident technology as a prerequisite for participation in C-TPAT and FAST. Finally, additional applications for FAST transponders should be pursued to improve security, safety, and efficiency in the border-crossing process.
How Pavement Markings Influence Bicycle and Motor Vehicle Positioning
Authors: Van Houten Ron , Seiderman Cara
Published: May 2018

The purpose of this study was to determine how pavement markings influence bicyclist and motorist positioning, particularly how far bicyclists travel from parked cars. The research examined the effects of the sequential addition of the component markings of a bicycle lane on a road with on-street parking in Cambridge, Massachusetts. The data measured were the distance that cars parked from the curb, the distance that bicyclists rode from the curb, and the distance that traveling motor vehicles drove from the curb. Data on bicyclists and moving motor vehicles were gathered by videotaping. The three pavement marking treatments–-an edge line demarcating the travel lane, the edge line and bicycle symbols, and a full bicycle lane–-were all effective at influencing bicyclists to ride farther away from parked cars than when no pavement markings were present. All three treatments significantly increased the percentage of cyclists riding more than 9 and 10 ft from the curb; these distances were used as benchmarks for where cyclists should ride to be farther from the opening-door zone of a parked car. There was variation between the signalized and the uncontrolled intersections. Before-and-after intercept surveys of cyclists and motorists were administered. In the before survey, cyclists most often responded that the best way to improve bicycling on Hampshire Street was to add bicycle lanes. Cyclists also rated the full bicycle lane most favorably in the after survey. There was no change in cyclist comfort levels between the before and the after surveys. When motorists were asked what made them most aware of cyclists on the street; the most common response in the before survey was “nothing.” In the after survey, the most common response was “the bicycle lane.”
User Perceptions of the Quality of Service on Shared Paths
Authors: Hummer Joseph E. , Rouphail Nagui , Hughes Ronald G. , Fain Shannon J. , Toole Jennifer L. , Patten Robert S. , Schneider Robert J. , Monahan John F. , Do Ann
Published: May 2018

Shared-use paths are becoming increasingly busy across the United States. Path designers need guidance on how wide to make new or rebuilt paths and on whether to separate the different types of users. The current guidance is not specific, has not been calibrated to conditions in the United States, and does not accommodate the range of modes found on a typical path. The purpose of this project, sponsored by FHWA, was to develop a level-of-service (LOS) estimation method for shared-use paths that overcomes these limitations. The focus of this paper is on the collection of the perceptions of path users and the development of a model relating those perceptions to operational and path variables. Companion papers describe the efforts made to develop equations explaining path operations and to develop an LOS estimation tool based on the perception model. For this effort, the project team collected the perceptions of 105 volunteers viewing 36 video clips from 10 paths. Analysis showed that variables related to path operations and the path width had the strongest relationships to the overall quality of the trail experience. The recommended model for overall rating included terms for path width, the number of meeting and passing events, and the presence of a centerline. The model was statistically sound; it should be easy to use. Analysts should be able to use the model and the procedure for determination of the LOS, which is based on the model, with confidence, knowing that it is well grounded on the perceptions of a large sample of trail users.
Level-of-Service Model for Pedestrians at Signalized Intersections
Authors: Petritsch Theodore A. , Landis Bruce W. , McLeod Peyton S. , Huang Herman F. , Challa Srikalyan , Guttenplan Martin
Published: May 2018

This paper documents a study performed to develop a level-of-service (LOS) model that accurately represents pedestrians’ perceptions of crossings at signalized intersections. This model incorporates perceived safety and comfort (i.e., perceived exposure and conflicts) and operations (i.e., delay and signalization). Data for the model were obtained from an innovative Walk for Science field data collection event and video simulations. The data consist of ( a) participants’ perceptions of safety, comfort, and operations as they walk through selected signalized intersections and ( b) the design and operational characteristics of these intersections. The resulting model provides a measure of the pedestrian's perspective on how well an intersection's geometric and operational characteristics meets his or her needs. The pedestrian LOS model for intersections described in this paper is based on Pearson correlation analyses and stepwise regression modeling of approximately 800 combined real-time perceptions (observations) from pedestrians walking a course through signalized intersections in a typical U.S. metropolitan area. The resulting general model for the pedestrian LOS at intersections is highly reliable, has a high correlation coefficient ( R2 = .73) with the average observations, and is transferable to the majority of metropolitan areas in the United States. Primary factors in the pedestrian LOS model for intersections include right-turn-on-red volumes for the street being crossed, permissive left turns from the street parallel to the crosswalk motor vehicle volume on the street being crossed, midblock 85th percentile speed of the vehicles on the street being crossed, number of lanes being crossed, pedestrian's delay, and presence or absence of right-turn channelization islands.
Accessible Pedestrian Signals
Authors: Scott Alan C. , Myers Linda , Barlow Janet M. , Bentzen Billie Louise
Published: May 2018

Push-button–integrated accessible pedestrian signals (APSs) provide audible information from the push-button housing on both the location of the push button and the onset of walk intervals. APS systems must provide clear, unambiguous information on which crosswalk has the walk interval. Push buttons in the United States, including push-button– integrated APSs, are inconsistently located, and APSs do not use consistent sounds to convey the “Walk” indication. The present research (NCHRP Project 3-62) investigated the effects of push-button placement and the type of audible “Walk” indication on visually or cognitively impaired participants’ ability to determine which of two streets had the “Walk” signal. Participants performed this task most quickly and most accurately when each push-button–integrated APS was mounted on its own pole, the poles were placed along the outer line (farthest from the center of the intersection) of the associated crosswalk, each pole was located within a few feet of the curb, and the audible “Walk” indication from each APS was a fast tick (percussive sound) at 10 repetitions per second. The results further indicate that where two push buttons are installed on a single pole, verbal “Walk” messages (e.g., “Seventh; walk sign is on to cross Seventh”) result in greater accuracy than two different sounds (fast tick and cuckoo) to signal the two crossings.
Field Comparison of Two Types of Accessible Pedestrian Signals
Authors: Williams Michael D. , Van Houten Ron , Ferraro John , Blasch Bruce B.
Published: May 2018

The effects of two types of accessible pedestrian signals on the street-crossing behaviors of 24 totally blind participants were directly compared in this research. One accessible pedestrian signal (APS) used a sound generator and vibrating hardware, which were integrated into the pedestrian push button (the Polara device). These sounds were heard from the near vicinity of the push button, and a different message or repetition rate was used to indicate the “Walk” interval. The second APS used pulsing light-emitting diodes to illuminate the message in the pedestrian signal head to transmit a message to a handheld receiver carried by the blind traveler (the Relume device). The handheld receiver provided a “Walk” or “Wait” message, designated by variable tones, which was audible only to the user. A control condition consisted of crossing without any APS device. Data were collected on crossing speed, the latency from the start of the walk and entering the crosswalk, the number of cycles missed, and the accuracy of the crossing. The results indicated that the time to cross the street was significantly shorter when participants used the handheld device than when they used the audible push-button device or crossed without any APS. There was no significant difference in crossing times between participants who used the audible push-button device and those who crossed without an APS under the control condition. The latency to start crossing was significantly faster when the participants used the handheld device than when they used the audible push button or crossed without an APS under the control condition. The number of missed cycles was significantly lower when the participant used either APS device than when the participant crossed without an APS device, and there was no difference in the number of missed cycles between the two APS devices.
Evaluating the Safety of Shared-Use Paths
Authors: Aultman-Hall Lisa , LaMondia Jeffrey
Published: May 2018

The project described in this paper involved the design of a survey of shared-use path safety for use at three facilities in Connecticut in the fall of 2002 and the summer of 2003. The objective was to collect self-reported information on collision and fall events and on travel exposure so that crash rates could be developed. The analysis of the self-reported events and travel patterns provides complementary data that are not available from other sources but are needed to address safety concerns on these facilities. The strengths of this approach include the collection of underreported minor events and the ability to estimate travel exposure and thus allow the estimation of crash rates per unit distance. The sample size of 684 was sufficient only for the development of aggregate crash rates, which suggest that skaters have the highest rates, followed by bicyclists and then pedestrians. The bicycle event rate was three times that of pedestrians, while the rate for skaters was more than six times that for pedestrians. Falls were more frequently reported than collisions, and they were more often associated with an injury. The overall incident rate for each of the three individual facilities was the highest for the path with the highest user volume and highest percentage of skaters and cyclists.
Multimodal Microsimulation of Vehicle and Pedestrian Signal Timings
Authors: Ishaque Muhammad M. , Noland Robert B.
Published: May 2018

A simple hypothetical network is analyzed with a microsimulation model to study the effects of signal cycle timings on the delay caused to both vehicles and pedestrians. Various vehicle types and pedestrians are introduced into the network, and their complete journeys are captured in the data output. Fixed-time noncoordinated signal cycles are defined at controlled junctions. Vehicle flows and signal cycle durations are varied while the other parameters, including pedestrian green phase timings, are held constant. Travel time delay information is disaggregated for vehicles and pedestrians for different signal timing scenarios. The results show that no single signal cycle timing can optimize the network delay for all types of flows. However, if the objective is to minimize the travel delay for all travelers, it is possible to find the optimal signal cycle length on the basis of the relative proportion of people using different modes.
Microsimulation Assignment Model for Multidirectional Pedestrian Movement in Congested Facilities
Authors: Abdelghany Ahmed , Abdelghany Khaled , Mahmassani Hani S. , Al-Gadhi Saad A.
Published: May 2018

Frequent pedestrian casualties in crowded facilities have brought increasing attention to the study of pedestrian dynamics in such facilities. In this paper, a microsimulation assignment model for multidirectional pedestrian movement in crowds is presented. The model attempts to overcome many limitations of existing models by incorporating various pedestrian behavior rules under a particular set of situations. It also adopts a cellular automata discrete system that allows detailed representation of pedestrians’ walkways and movement areas. The model is applied to the “mataf” system, which is located at the main prayer hall of the holy noble mosque known as Al-Haram Al-Shareef Mosque in Mecca, Saudi Arabia. A set of simulation experiments is designed to illustrate use of the model to study the performance of the mataf system by consideration of different operational conditions as well as different pilgrim behavior rules.
Design and Performance Analysis of Pedestrian Crossing Facilities for Continuous Flow Intersections
Authors: Jagannathan Ramanujan , Bared Joe G.
Published: May 2018

Although concepts of the continuous flow intersection (CFI) have been around for approximately four decades, minimal or no literature describing studies that have analyzed pedestrian traffic performance at these intersections is available. Several studies have reported on the qualitative and quantitative benefits for the vehicular traffic performance of CFIs in comparison with the benefits for the vehicular traffic performance of conventional intersections but have provided minimal or no discussion about pedestrian traffic performance. As a novel intersection design, many important considerations are required to design pedestrian accesses and crossings at CFIs without compromising pedestrian safety and vehicular traffic performance. In this paper, the design methodologies for providing pedestrian access and related pedestrian signal timings are discussed. Modeling was conducted on three typical geometries for CFIs with base signal timings optimized for vehicular traffic performance. The results indicate an acceptable pedestrian level of service of B or C on the basis of the average delay per stop experienced by any pedestrian for pedestrian crossings at the typical CFI geometries modeled. All pedestrians served at the CFIs are accommodated within two cycles for a typical signal cycle length ranging from 60 to 100 s.
Influence of Winter Road Conditions and Signal Delay on Pedestrian Route Choice in Japan's Snowiest Metropolis
Authors: Muraleetharan Thambiah , Meguro Kunio , Adachi Takeo , Hagiwara Toru , Kagaya Sei'ichi
Published: May 2018

Investigation of pedestrian route choice behavior on icy surfaces is important for the effective improvement of walkways in winter. The objective of this research was to investigate pedestrian route choice behavior in winter. Field surveys and questionnaire surveys were conducted to fulfill this objective. Video cameras were used in the field surveys to clarify the movements of pedestrians. How pedestrians chose their routes was investigated by observing their movements. According to the field survey, when the signal was green, the probability that the pedestrian would cross became extremely high, regardless of the road surface conditions. However, when the walkway surface was icy, the probability that the pedestrian would wait for a green signal decreased by a considerable value. This indicates that when the wait becomes long, the probability that the pedestrian will cross becomes low during the snowy season. A questionnaire survey was also conducted to clarify the factors affecting pedestrian route choice behavior. The questionnaire asked about different road surface conditions. The results from the survey indicate that even if part of a road section has a good surface condition, it has a strong influence on route choice behavior. It indicates that pedestrians feel uncomfortable in walking on slippery walkways and they prefer to choose bare walkways. On the basis of the data from the field survey and questionnaire survey, logit models were developed to express quantitatively the route choice behaviors of pedestrians. These models can be used to predict the probability that a pedestrian will select a route as a function of pedestrian delay at signalized intersections and the road surface conditions in winter.
Equity Impacts and Challenges of Highway Access Management in an Emerging Economy
Authors: Page Oliver
Published: May 2018

As a middle-income country, South Africa realizes that it cannot build its way out of every transportation challenge that it faces. Alternative interventions have a role to play in optimizing the efficiency of the present transportation network while ensuring that the benefits from this optimization are distributed equitably. The implementation of the proposed Guidelines on Road Access Management in South Africa is one such intervention that may equitably improve the transportation environment. This paper describes the evolution and status quo of access management in South Africa, assesses the concept and purpose of access management from an equity perspective, considers the efficacy of implementing national access management guidelines while honoring the equity principles contained in the South African constitution and other civil laws and regulations, and assesses a selection of access management techniques with respect to their potential equity impacts. The paper identifies a selection of obstacles that have frustrated the adoption and implementation of access management principles on a national scale. Inconsistency in the implementation of access management principles, which is inevitable when there is no mandated national guideline, compounds the level of inequity manifested by ad hoc highway access permitting and management. Thus, it is concluded that the adoption and implementation of a national access management guideline will measurably enhance the potential of equitably improving the transportation environment in South Africa.