Virginia P Sisiopiku

Relationship Between Volume-to-Capacity Ratios and Accident Rates

The general relationships between hourly accident rates and hourly traffic volume/capacity (v/c) ratios were examined. A 26 km (16 mi) segment of Interstate I-94 in the Detroit area was selected as the study segment. The v/c ratios were calculated from average hourly traffic volume counts collected in 1993 and 1994 from three permanent count stations. Accident rates were derived from hourly distributed number of accidents in the same 2 years. The correlation between v/c values and accident rates follows a general U-shaped pattern. The study of all observed accidents combined indicates that accident rates are highest in the very low hourly v/c range, decrease rapidly with increasing v/c ratio, and then gradually increase as the v/c ratio continues to increase. U-shaped models also explain the relationship between v/c and accident rates for weekdays and weekend days, multivehicle, rear-end, and property-damage-only accidents. On the other hand, single-vehicle, fixed-object, and turnover accidents, and accidents involving injury and fatality follow a generally decreasing trend with increasing v/c ratio. Traffic conflict is viewed as a major contributing factor to high accident rates observed in the high v/c range, whereas night conditions and driver inattention were identified as explanatory factors for the occurrence of high accident rates in the low v/c ranges.

Impact of distracted driving on safety and traffic flow.

Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16-25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner that impacts safety and traffic flow negatively when distracted.

Study of the Impact of Police Enforcement on Motorists' Speeds

One method to enforce speed limits on U.S. highways is through the use of police enforcement. One major problem with this approach is the high cost associated with the employment of police officers for patrolling purposes. Thus, the effectiveness of police presence in controlling highway speeds should be carefully assessed prior to making a decision on increasing police patrolling operations on the transportation network. A study was undertaken to evaluate the effects of police presence on the speed of vehicles in a recently increased speed-limit zone and to determine the “halo” effects of police presence (lasting effects when police are gone) on vehicular speeds. Data were collected on Interstate 96 in Ionia County, Michigan. Marked police cars circulated in both directions on the study segment, which was approximately 45 km (29 mi) long. Net speed reductions at a distance of 1.6, 3.2, and 4.8 km (1, 2, and 3 mi) upstream and downstream of each counter were used in the data analysis. Two methods were applied to study the effects of police presence. First, the average speed in the area without the police presence was compared to the average speed after the police presence. Second, the difference between the speed at the place where the police vehicle was positioned and the speed downstream was calculated. It was found that the average speed just upstream of the police car’s location was reduced, but as soon as vehicles passed the patrol car, drivers accelerated to their normal speeds or more. Moreover, no “halo” effects on the vehicles at the increased speed zone under study were observed.

Community-based pedestrian safety training in virtual reality: A pragmatic trial

Child pedestrian injuries are a leading cause of mortality and morbidity across the United States and the world. Repeated practice at the cognitive-perceptual task of crossing a street may lead to safer pedestrian behavior. Virtual reality offers a unique opportunity for repeated practice without the risk of actual injury. This study conducted a pre-post within-subjects trial of training children in pedestrian safety using a semi-mobile, semi-immersive virtual pedestrian environment placed at schools and community centers. Pedestrian safety skills among a group of 44 seven- and eight-year-old children were assessed in a laboratory, and then children completed six 15-minute training sessions in the virtual pedestrian environment at their school or community center following pragmatic trial strategies over the course of three weeks. Following training, pedestrian safety skills were re-assessed. Results indicate improvement in delay entering traffic following training. Safe crossings did not demonstrate change. Attention to traffic and time to contact with oncoming vehicles both decreased somewhat, perhaps an indication that training was incomplete and children were in the process of actively learning to be safer pedestrians. The findings suggest virtual reality environments placed in community centers hold promise for teaching children to be safer pedestrians, but future research is needed to determine the optimal training dosage.

Winter road maintenance-ITS options

Winter road maintenance operations are of great importance for driver convenience and safety. Keeping US roads safe for winter travel is a

The Impact of Billboards on Driver Visual Behavior: A Systematic Literature Review

2.1 billion proposition annually for State and local agencies. The US Department of Transportation and State and local agencies have been looking into the application of ITS technologies and products toward the improvement of winter maintenance operations. The paper reviews potential applications of ITS for winter maintenance, discusses technologies involved and benefits from technology implementation and provides examples of case studies.

Modeling vehicle–pedestrian interactions outside of crosswalks

Objective: External distraction appears to affect at least 6–9% of distraction-affected motor vehicle collisions. Billboards may be good models for studying external distraction in general, and it is also desirable to understand billboard-related distraction per se. However, there has not yet been a clear consensus on the scope of billboard-related distraction or its dynamics with respect to characteristics of drivers, billboards, traffic, and the roadway. To narrow these knowledge gaps, a systematic literature review was conducted on billboard-related changes in driver visual behavior. Methods: A systematic literature search yielded 443 results, of which 8 studies met all inclusion criteria. Five studies meeting all inclusion criteria were later identified and added. Results were analyzed in terms of 4 categories of visual behavior: (1) gaze variability (GV), glance pattern activity (GPA), and percentage of time spent glancing at the forward roadway; (2) glances at unexpected drive-relevant stimuli; (3) glances at expected drive-relevant stimuli; and (4) glances at billboards. Results: There was considerable evidence that about 10–20% of all glances at billboards were ≥0.75 s, that active billboards drew more glances and more long glances (≥0.75 s, ≥2.0 s) than passive billboards but did not attract a longer average glance, and that there was large variability among individual billboards within categories (e.g., active vs. passive). The extent to which billboards attracted glances ≥ 2.0 s was uncertain. There was tentative evidence that billboards did not affect GPA, glances at expected drive-relevant stimuli, or the proportion of time drivers spent glancing at the forward roadway and that they did affect vertical GV and glances at unexpected drive-relevant stimuli. Conclusions: Generally, billboard-related distraction appeared to be minor and regulated by drivers as the demands of the driving task changed. However, this reviews findings suggest that this may not be true in all cases. Future research should emphasize the tails of the distribution in addition to average cases, in terms of both the analysis of visual behavior and the complexity of driving tasks. Further research is also needed to understand the effects of billboard design, driver characteristics, and road and traffic context.

Issues, Practices, and Needs for Communicating Evacuation Information to Vulnerable Populations

Abstract Pedestrian and driver behaviors as well as their interactions, are essential in planning, designing and operating highway facilities. Pedestrian crossing outside of a marked or unmarked crosswalk (i.e. jaywalking), is one of those pedestrian behaviors that may highly affect safety and operations. Unlike permissible crossings at crosswalks, jaywalking events are not often anticipated by drivers, which may result in less driver reaction time and different vehicle operation dynamics. It is important to understand pedestrian crossing behavior outside of crosswalks, as well as driver yielding behavior towards them. To date, limited quantitative and behavioral research has been conducted to investigate this interaction or simulate it microscopically. This paper aims to explore both pedestrian jaywalking behavior (gap acceptance and speeds) and the corresponding driver reactions (yielding behavior) for modeling the vehicle–pedestrian interactions (VPI) outside the crosswalks in a micro-simulation environment. The study also quantifies the differences between vehicle–jaywalker and vehicle-permissible crossing. An observational study and an instrumented vehicle study were conducted on the campus of the University of Florida to collect data from pedestrian and driver perspectives, respectively. Crossing speed, yield acceptance and delay of jaywalking crossings and permissible crossings were observed in the study and these attributed can be used for replicating pedestrian operations in simulators. Moreover, behaviors of driver approaching jaywalkers versus pedestrians crossing at designated crosswalks were compared on the basis of yield rates, and vehicle speed profiles. Vehicle yield dynamics were analyzed to model the driver reactions towards jaywalkers. Lastly, it was found that the locations of jaywalking events are highly concentrated and influenced by the crossing environment, such as pedestrian and vehicular volume, bus stops presence and crossing distance. This paper establishes several quantitative relationships describing interactions between pedestrians crossing outside of crosswalks and approaching drivers, which provide the basis and assumptions for modeling such interactions in a micro-simulation environment for traffic operational analyses.

Application of Level-of-Service Methods for Evaluation of Operations at Pedestrian Facilities

Effective communication of transportation-related information to vulnerable populations is a critical need during emergencies. Despite its importance, various factors still hinder the development of comprehensive and effective plans for communicating emergency information to mobility-limited individuals during evacuations and other major emergencies. Such limiting factors include the wide diversity of vulnerable populations, their special needs, existing contact and communication barriers, and lack of resources and mechanisms to locate those populations and assist them during emergencies. This paper illustrates the complexity of communicating with vulnerable populations in emergency evacuations through a critical review of the existing literature and state-of-the-practice information gathered recently from transportation and emergency management agency personnel. First, the paper reviews definitions, characteristics, and size of the vulnerable population. Next, principles of effective communication and the special provisions for communicating with vulnerable populations are presented, along with examples of effective communications and communications barriers. Finally, the paper identifies numerous important emergency evacuation communications topics that were not discussed in the literature and offers recommendations for bridging those gaps. Examples include the limited involvement of experts in emergency evacuation communication, the lack of information about the financial aspects and cost-effectiveness of such communications, the need to establish an information clearinghouse to assist in future evacuations, and the lack of standardization and cataloging of appropriate evacuation messages. The paper is presented as a foundation for developing a framework for effective communications strategies, policies, and practices that focus on vulnerable populations before, during, and after all-hazards emergencies.

Role of Transit in Carless Evacuation Planning

Several methods for assessment of the quality of operations of pedestrian facilities on the basis of pedestrian level of service (LOS) have been proposed. Some of these methods use the principles of vehicular traffic to evaluate pedestrian traffic operations. Other methods are more concerned with the facility design and walking environment than with the actual pedestrian flows. To draw a complete picture of LOS determination methods for pedestrian facilities, it is necessary to review, compare, and contrast the various methods in the literature that assess quality of service for pedestrian facilities. This paper compares some of the more common and widely accepted methods for determination of the pedestrian LOS at sidewalks. These include the Highway Capacity Manual 2000 method, the Australian method, the Trip Quality method, the Landis model, and the conjoint analysis approach. After the methods and their associated measured criteria are described, a total of 13 sidewalks at two study sites were evaluated. The study sites are located in the downtown area of Birmingham, Alabama, and represent pedestrian operations at urban sidewalks. The comparison provides useful information on the consistency of the outcomes from the various methods and identifies needs for modifications and improvements. This is particularly useful in determining possible improvements to the existing Highway Capacity Manual 2000 method in the upcoming version of the Highway Capacity Manual.