Aemal Khattak

Effects of work zone presence on injury and non-injury crashes.

Work zones in the United States have approximately 700 traffic-related fatalities, 24,000 injury crashes, and 52,000 non-injury crashes every year. Due to future highway reconstruction needs, work zones are likely to increase in number, duration, and length. This study focuses on analyzing the effect of work zone duration mainly due to its policy-sensitivity. To do so, we created a unique dataset of California freeway work zones that included crash data (crash frequency and injury severity), road inventory data (average daily traffic (ADT) and urban/rural character), and work zone related data (duration, length, and location). Then, we investigated crash rates and crash frequencies in the pre-work zone and during-work zone periods. For the freeway work zones investigated in this study, the total crash rate in the during-work zone period was 21.5% higher (0.79 crashes per million vehicle kilometer (MVKM)) than the pre-work zone period (0.65 crashes per MVKM). Compared with the pre-work zone period, the increase in non-injury and injury crash rates in the during-work zone period was 23.8% and 17.3%, respectively. Next, crash frequencies were investigated using negative binomial models, which showed that frequencies increased with increasing work zone duration, length, and average daily traffic. The important finding is that after controlling for various factors, longer work zone duration significantly increases both injury and non-injury crash frequencies. The implications of the study findings are discussed in the paper.

Comparative Analysis of Spatial Knowledge and En Route Diversion Behavior in Chicago and San Francisco: Implications for Advanced Traveler Information Systems

Drivers’ spatial knowledge and en route response to unexpected delay information are examined. Compared are behavioral responses to information across two metropolitan areas in the United States: Chicago and the San Francisco Bay Area. Comparable behavioral data were collected through handout-mailback questionnaires targeting peak-period automobile commuters. The Chicago respondents perceived higher traffic congestion levels, and more of them knew one or more alternate routes. Among the Chicago respondents, fewer received information about unexpected delays from the radio (as opposed to self-observation of congestion) and more automobile commuters diverted to their alternate routes. To understand the factors that influence knowledge of alternate routes and en route diversion in response to unexpected congestion, a full information maximum likelihood nested logit model is estimated. Results of the model indicate that longer duration of residence, higher propensity for discovering new routes, and locational characteristics tend to increase drivers’ spatial knowledge. Propensity for en route diversion increases with higher than usual route travel time plus delay and shorter alternate route travel times. Drivers with higher propensity for taking risks to avoid unexpected delays are more likely to divert. The model indicates that route knowledge and en route diversion propensity is higher in Chicago than San Francisco. This implies that information-sensitive behavioral models may be context dependent. Importantly, delay information received through radio traffic reports, as opposed to other sources such as self-observation of congestion, increases en route diversion propensity in unexpected delay situations. This implies a more dynamic readjustment of commuters’ route selection decisions. At the same time, the potential benefits from Advanced Traveler Information Systems (ATIS) must compete with the benefits already accruing from radio traffic information.

Interstate Highway Crash Injuries During Winter Snow and Nonsnow Events

Many regions across the United States experience a number of winter snow events every year, during which a multitude of vehicular crashes occur. The authors formally compare crashes and occupant injuries reported on Interstate highways in Iowa during winter snow event periods with those reported during equivalent winter nonsnow event periods. The comparison is fairly comprehensive because it includes detailed crash, weather, and roadway geometry information on seven different sections of the Iowa Interstate highway system. Further, the analysis utilizes traffic count data specific to snow event and comparable nonsnow event periods. The comparison was facilitated by using a geographic information system that merged data from a variety of sources, resulting in the creation of a unique data set with significant spatial and temporal coverage. After explicitly controlling for seasonal, monthly, weekly, hourly, and locational variations in crash occurrence, significant increase was observed when winter snow event injury and noninjury crash rates (crashes per million vehicle kilometers) were compared with equivalent winter nonsnow event injury and noninjury crash rates. The data were then analyzed for injury occurrence. Results of a logit model indicated that crash injury occurrence on Interstate highways in Iowa depended on traffic, road geometry, and number of vehicles involved in a crash. Another finding from the logit model was that crashes during snow events were less injurious compared with equivalent nonsnow event crashes. Snow event–specific crash data were then analyzed to study the effects of snow event elements (e.g., snowfall intensity) on injury occurrence in vehicular crashes.

Pedestrian and Bicyclist Violations at Highway–Rail Grade Crossings

Each year numerous pedestrian and bicyclist crashes involving high injury levels are reported at highway–rail grade crossings (HRGCs) across the United States. Such crashes are invariably the result of errors on the part of the pedestrians and bicyclists. The focus of this paper is to investigate pedestrian and bicyclist violations at a dual-quadrant gated HRGC and to report on four types of gate violations, including factors associated with those violations. For both pedestrians and bicyclists, the violations studied were (a) passing under descending gates, (b) passing around fully lowered gates, (c) passing under ascending gates, and (d) passing around fully lowered gates between successive trains. Data on pedestrian and bicyclist violations were collected at a grade crossing in Nebraska through the use of video surveillance. Analysis indicated that there were no significant differences in the mean frequencies of pedestrian and bicyclist violations at HRGCs. When data for pedestrians and bicyclists were pooled, 1.27 gate-related violations were recorded per crossing event. Children of around 8 years of age or younger were involved in 25% more gate-related violations than older crossing users (pedestrians and bicyclists). Violations increased with the presence of more individuals at the crossing during train crossing events, but the contribution from young children was greater than that from older crossing users. The implications of the findings for HRGC safety are discussed.

Application of Light Detection and Ranging Technology to Highway Safety

An application of light detection and ranging (LIDAR) technology to highway intersection safety is presented. LIDAR can be used to collect information about a surface by reflecting thousands of light beams per second off the surface and measuring the return time of the beams. The surface profile is collected as a digital signature that can be used in a variety of applications. Collection of information on the surface profile of the earth in the form of elevation data is one of several LIDAR applications that have been used for mapping and contouring. The focus of the described application is use of LIDAR elevation data to obtain information on intersection geometry that can lead to the discovery of potential obstructions in driver sight lines. After appropriate transformations, LIDAR elevation data were used in line-of-sight analysis to obtain information on sight-line obstructions at six intersections on the IA-1 corridor in Iowa. Intersection crash frequency and data availability were considerations in the selection of the six intersections. Results from the line-of-sight analysis were validated by visits to the intersections in the field and verification of the existence of obstructions detected during the analysis. Sixty-six lines of sight were blocked during the line-of-sight analysis, of which 62 (89.8%) were confirmed during the validation process. Four (5.8%) sight-line obstructions were not confirmed during the validation. At least three (4.4%) potential sight-line obstructions discovered during validation were not detected during the line-of-sight analysis. The intersection with the highest crash frequency was correctly found to have obstructions located within the intersection sight triangles. It can be concluded that LIDAR elevation data can be used successfully for identifying potential sight-distance problems at intersections. Identified potential problems can be verified and rectified in the field. LIDAR is a relatively costly data source, and a single application, such as this one, cannot justify the high cost of LIDAR data acquisition. Other potential highway safety enhancing applications of LIDAR must be investigated to offset the high data-acquisition cost. Suggestions for other highway safety applications are provided.

HUMAN FATALITIES IN ANIMAL-RELATED HIGHWAY CRASHES

Recent national and statewide trends in the relatively uncommon animalrelated highway crashes that involve human fatalities were reviewed. Highway crashes in which animals are struck by vehicular traffic regularly occur throughout the United States. Invariably, such crashes are most damaging to the struck animals, while injuries to humans are usually not as severe. As such, significant research has focused on the plight of animals involved in traffic crashes. However, over the past decade animal-related crashes in the United States have claimed 1,353 human lives, costing the nation well over

Gate Rushing at Highway—Railroad Grade Crossings: Drivers' Response to Centerline Barrier

1 billion in losses. The research reported focuses on recent national and statewide trends in fatality-producing animal-related vehicular crash frequencies and rates. Additionally, the temporal aspects of these crashes and trends in human and vehicle involvement in these crashes were investigated. The analysis used Fatality Analysis Reporting System data from 1991 to 2000, which were combined with data from other sources in a geographic information system. Analysis of the integrated data indicated that fatality-producing animal-related crashes are increasing nationally and that this trend is attributable to increasing vehicle miles traveled. The rate for fatality-producing animal-related crashes is holding steady at the national level. Human fatalities in such crashes occur at times when animals are more active, and unrestrained persons are more often killed than restrained persons. The information presented is suitable for agencies assessing the issue of human fatalities in animal-related crashes and for driver education and awareness programs.

New and existing roadway inventory data acquisition methods

This paper deals with the issue of aggressive motor vehicle drivers rushing through closed gates or gates in motion when trains are in close proximity to a highway–railroad grade crossing. The papers objectives were to report drivers’ frequency of gate rushing and factors associated with it and to investigate drivers’ response to varying degrees of control exercised on their ability to rush through gates. Motor vehicle drivers at a highway–railroad grade crossing were observed by using video equipment before and after a plastic and rubber barrier was installed along the roadway centerline on both sides of the crossing. The installation was in two stages that progressively limited drivers’ ability to go through closed gates. During the first stage, the barriers on both sides of the crossing were installed such that they stopped short of the gates, while in the second stage they were fully extended to the gates. The expectation was that gate rushing will diminish when the barrier is erected but stops short of the gates and that it will further diminish when the barrier is fully extended to the gates. Data analysis showed a gate rush occurring about once every five train crossings; installation of the barrier along the roadway centerline on both sides of the crossing during the first stage reduced gate rushing by 37%. Contrary to the authors’ expectations, no additional reduction in gate rushing was observed when the barriers were fully extended to the gates. Instances of gate rushing increased with longer durations of road closures but decreased if crossing trains stopped on the tracks or if weather conditions were not favorable.

Comparison of Driver Behavior at Highway-Railroad Crossings in Two Cities

The paper reports the results of a study to compare two data collection methods used to collect roadway inventory data: the traditional manual method and the advanced mobile mapping method using state of the art imaging, georeference, and software technologies. Four experiments examine descriptive inventory data collected by the two methods, considering data accuracy in different roadway environments, type of inventory element, and data collection time. Because there are mobile mapping systems with different technological characteristics, the four experiments use four different mobile mapping systems to cover the spectrum of various systems available for data collection.

Driver Characteristics Associated with Knowledge of Correct Roundabout Negotiation

This paper attempts to answer two questions pertaining to highway–railroad grade crossing (HRGC) safety. First, does unsafe driver behavior differ at HRGCs located in two cities? Second, is there a difference in drivers’ response to the same safety treatment at two HRGCs? The two HRGCs investigated are in Waverly and Fremont, Nebraska. Unsafe behaviors investigated at both locations were passing around closing or closed gates and making U-turns while waiting for trains to pass. The safety treatment used at the HRGCs was a barrier installed along the street center leading up to the gates that made it difficult for drivers to engage in unsafe maneuvers. Analysis of the collected data showed that drivers in Waverly engaged in more frequent gate passing compared with drivers in Fremont. Conversely, drivers in Fremont more frequently made U-turns at HRGCs. Installation of the barrier reduced gate passing and U-turns at both locations; the percentage of reductions in gate passing and U-turns at the two locations were comparable. Based on the results, the conclusions are that drivers’ unsafe behavior at HRGCs is location-dependent, but the order of magnitude of drivers’ response to the same safety treatment at different locations is quite similar.