Traffic Safety Evaluation Research Articles

Obesity and non-fatal motor vehicle crash injuries: sex difference effects

BackgroundObesity and motor vehicle crash (MVC) injuries are two parallel epidemics in the United States. An important unanswered question is if there are sex differences in the associations between the presence of obesity and non-fatal MVC injuries.ObjectivesTo further understand the association between obesity and non-fatal motor vehicle crash injuries, particularly the sex differences in these relations.MethodsWe examined this question by analyzing data from the 2003 to 2007 National Automotive Sampling System Crashworthiness Data System (NASS CDS). A total of 10, 962 drivers who were aged 18 years or older and who survived frontal collision crashes were eligible for study.ResultsMale drivers experienced a lower rate of overall non-fatal MVC injuries than did female drivers (38.1% vs. 52.2%) but a higher rate of severe injuries (0.7% vs. 0.2%). After adjusting for change in velocity (ΔV) during the crashes, obese male drivers showed a much higher risk [logistic coefficients of BMI for moderate, serious, and severe injury are 0.0766, 0.1470, and 0.1792, respectively; all p<0.05] of non-fatal injuries than did non-obese male drivers and these risks increased with injury severity. Non-fatal injury risks were not found to be increased in obese female drivers. The association between obesity and risk of non-fatal injury was much stronger for male drivers than for female drivers.ConclusionThe higher risk of non-fatal MVC injuries in obese male drivers might result from their different body shape and fat distribution compared with obese female drivers. Our findings should be considered for obesity reduction, traffic safety evaluation and vehicle design for obese male drivers and provide testable hypotheses for future studies.

Evaluation of traffic safety, based on micro-level behavioural data: Theoretical framework and first implementation

A traffic encounter between individual road users is a process of continuous interplay over time and space and may be seen as an elementary event with the potential to develop into an accident. This paper proposes a framework for organising all traffic encounters into a severity hierarchy based on some operational severity measure. A severity hierarchy provides a description of the safety situation and trade-off between safety and efficiency in the traffic system. As a first approach to study the encounter process, a set of indicators is proposed to describe an encounter. These indicators allow for a continuous description even if the relationship between the road users changes during the process (e.g., when they are on a collision course or leave it). Automated video analysis is suggested as a tool that will allow data collection for validation of the proposed theories.

A traffic safety evaluation of California's traffic violator school citation dismissal policy

Introduction This study evaluated California's traffic violator school (TVS) citation dismissal policy. Method This study identified and compared two large samples of drivers either completing a TVS (N = 210,015) or convicted of a traffic citation (N = 168,563). Results Prior to adjudication, the TVS group had characteristics (e.g., lower prior conviction rate and smaller proportion of males) that were predictive of a lower subsequent crash risk. However, the TVS group exhibited significantly more crashes than did the convicted group in the subsequent one-year period. The difference (4.83%) increased to 10% after adjusting for the more favorable characteristics of the TVS group. The TVS group also had a higher adjusted subsequent crash rate at each prior driver record entry level, reflecting a loss in the general and specific deterrence of the non-conviction masked status of TVS dismissed citations. It was reported that the TVS dismissal policy results in approximately 12,300 additional crashes annually with economic costs of approximately $398,000,000. Conclusions The avoidance of licensing actions resulting from the dismissal policy assists in explaining why the driving public is exposed to an increased crash risk. A number of recommendations are offered to reduce the negative traffic safety impact of the TVS citation dismissal policy.

Mobile mapping technology of wind velocity data along highway for traffic safety evaluation

Traffic safety of highway vehicles under strong crosswind gust and other hazardous driving conditions has become a pressing issue for modern highway transportation and economy. It is known that the actual wind environment at the typical height of a moving vehicle varies considerably from one segment to another even on the same highway, because of influence of the specific terrain and surroundings. Therefore, accurate crosswind velocity data in both time and spatial domains are needed, for a rational assessment of traffic safety risks for various moving vehicles on highways in windy conditions. In addition to site-specific wind data which can be used for most vehicles, vehicle-specific crosswind velocity is often required for an accurate safety assessment of high-sided vehicles with unique shapes. A mobile mapping technology aiming at collecting site-specific as well as vehicle-specific wind velocity data for traffic safety evaluations was developed. Such technology integrates a 3D sonic anemometer and geospatial video mapping system, mounted on a vehicle driven along highways at a normal (cruising) speed. As a result, both vehicle-specific and general site-specific crosswind velocity can be directly “sensed” and collected by using a high-sided vehicle or a streamlined car as the test vehicle. A field test of the developed technology with a high-sided truck driven on mountainous sections of the interstate I-70 (in Colorado) was conducted. The crosswind data at six selected feature locations along I-70, representing different roadside environments, was analyzed. Wind-tunnel investigations employing the scaled models of the truck used in the field test as well as a common streamlined sedan car were conducted to evaluate the accuracy and the feasibility of the developed technology.

Traffic Microsimulation Modeling to Study a Traffic Signal Incident Reduction Function

This paper demonstrates the use of a discrete event traffic micro-simulation model to study the safety impacts of the introduction of an incident reduction (IR) function into a vehicle-actuated traffic signal controller. The IR function is based on that used in signal controllers in Sweden. The IR function is designed to reduce the number of stop-or-go decisions by drivers when caught in the dilemma zone at the onset of the amber signal. A correctly adapted IR function was found to greatly enhance the safety performance of signalized intersections. The simulation experiment described in the paper is based on empirical data from a suburban vehicle-actuated signalized intersection. It was conducted specifically to investigate the effects of the standard IR function on three proximal safety indicators: time to collision, red light violations, and required braking rates. The simulation results demonstrate a significant improvement in the time to collision (22%), red light violations (6%), and required braking rate when the IR function was in operation and a small positive influence on traffic movement through the intersection. Importantly, this study has illustrated the potential for using traffic microsimulation modeling for traffic safety evaluation.

Traffic Safety Evaluation in Signal Charge Intervals Considering the Effect of Right Turn Phase

In this research, vehicle behaviors at the signal change intervals in signalized intersection are analyzed and characteristics of the occurrence of unreasonable vehicle behaviors at the signal change intervals are identified. Based on the analysis, accident probabilities in the intersection are estimated with supposing that any avoidance behaviors are not done by vehicle drivers. It makes clear the danger caused by such unreasonable vehicle behaviors, and it makes possible to evaluate quantitatively the danger at the signal change intervals in signalized intersections.

Derivation and Validation of New Simulation-Based Surrogate Safety Measure

Traffic safety evaluation is one of the most important processes in analyzing transportation systems performance. Traditional methods like statistical models and before-after comparisons have many drawbacks, such as limited time periods, sample size problems, and reporting errors. The advancement of traffic conflict techniques combined with microsimulation offers a potentially innovative way for conducting safety assessment of traffic systems even before safety improvements are implemented. In this paper, simulation-based safety studies are reviewed, and a modified simulation-based surrogate safety measure and a new simulation-based surrogate safety measure that can capture the probability of collisions, as well as the severity of these potential collisions, are proposed. Conceptual and computational logic of the proposed surrogate safety indicators are described in detail. These surrogate safety indices are initially proposed for link-based analysis and should not be used for other purposes, such as intersection safety assessment, without further enhancements, and the use of these indices should be limited to the analysis of linear conflicts. In addition, these link-based indices are extended to be able to conduct aggregate networkwide safety assessments. The proposed indices are validated by means of a well-calibrated traffic simulation model of a section of the New Jersey Turnpike and real accident data from the same section. Preliminary results indicate a strong relationship between the proposed surrogate safety measures and real accident data. Further research is needed to investigate these new surrogate safety indices under different locations and traffic conditions.

Forecasting and evaluation of traffic safety impacts: driving assistance systems against road infrastructure measures

The authors examine the use of a one-variable first-order grey model ( GM( 1,1)), to model and forecast the trend of the level of cumulative traffic accident severity for strategic scenarios for implementation of driving assistance systems, physical infrastructure redesign and combinations of the two categories of measures. The accident severity levels ( in terms of fatalities and hospitalisations) of five scenarios for the period 2003-2007 are analysed and modelled. In addition, the trend of fatalities and hospitalisations for each scenario for the years 2008 until 2010 is forecasted. For further policy evaluation, the costs of each scenario ( for the years 2003 2010) are estimated. By using cost-effectiveness analysis (CEA) the five scenarios for improving road traffic safety are compared. (Less)

Investigation of Regression-to-Mean Effect in Traffic Safety Evaluation Methodologies

Observational before-and-after safety evaluations have been commonly used to determine the effectiveness of safety improvements applied to high-crash locations. Such evaluations may typically be affected by regression-to-mean (RTM) bias. This research compares the effectiveness of low-cost safety improvements applied to several high-crash intersections in the cities of Detroit and Grand Rapids, Michigan, and examines the RTM effects by using various safety evaluation methodologies. Some previous studies suggest that before-and-after studies are always biased. It is also claimed that the observed number of crashes cannot be used to determine the effectiveness of safety improvements, and the use of the empirical Bayes (EB) method is suggested. This research examines the RTM effects by using before-and-after studies, before-and-after studies with control sites, and two different variants of the EB method. The research reveals that the expected crash frequencies computed by various evaluation methods do not differ significantly when 3 to 5 years' worth of traffic crash data are used. The deviations of the expected crash frequencies with the before-and-after methods and the EB method are computed to compare the RTM effects for each additional year of traffic crash data used in the evaluation. This research reveals that before-and-after studies produce results similar to those of the EB method, and the RTM effect becomes insignificant when 3 or more years' worth of traffic crash data are used in the evaluation of high-crash locations.

Traffic Safety Evaluation of Video Advertising Signs

Road authorities are under increasing pressure from advertisers to allow video advertising in the right-of-way but are understandably concerned about whether video signs constitute a driving hazard. At the City of Toronto's request, a comprehensive assessment of traffic safety impacts related to such signs was carried out in a series of studies involving three downtown intersections and an urban expressway site. An on-road eye fixation study was carried out to determine if drivers look at video advertising signs. Conflict studies were conducted to determine if there were more conflicts on intersection approaches with visible video signs than on those without such signs. A before-and-after sign installation study of headways and speeds on the urban expressway was carried out. Crashes were compared before and after sign installation at the expressway and three intersection sites. Finally, a public survey was conducted to determine if video advertising was perceived to affect traffic safety. On the basis of the eye fixation study and the public survey data, it is apparent that video advertising can distract drivers inappropriately and lead to individual crashes. However, the evidence from other studies was not consistent and suggests that for the particular signs studied, overall impacts on traffic safety are likely to be small. Further studies, especially prospective ones with larger crash data sets, are required to be certain about the findings. A comparison between this study and an earlier one suggests that there are large differences in driver distraction depending on the placement and the environment in which the sign is seen. Further studies are required to determine factors that minimize driver distraction.

Traffic Safety Evaluation of Video Advertising Signs

Road authorities are under increasing pressure from advertisers to allow video advertising in the right-of-way but are understandably concerned about whether video signs constitute a driving hazard. At the City of Toronto's request, a comprehensive assessment of traffic safety impacts related to such signs was carried out in a series of studies involving three downtown intersections and an urban expressway site. An on-road eye fixation study was carried out to determine if drivers look at video advertising signs. Conflict studies were conducted to determine if there were more conflicts on intersection approaches with visible video signs than on those without such signs. A before-and-after sign installation study of headways and speeds on the urban expressway was carried out. Crashes were compared before and after sign installation at the expressway and three intersection sites. Finally, a public survey was conducted to determine if video advertising was perceived to affect traffic safety. On the basis of ...

Statistical modelling and evaluation of aircraft collision risk using correlation theory

The method of statistical modelling and evaluation of collision probability is offered. It can make a methodological basis for an evaluation of air traffic safety, and also to be applied to detection of potential conflict situations while air traffic control. For the mathematical description of predicted air traffic movement, and for the evaluation of collision probability the correlation functions of deviation process from planned flight trajectory are used. The procedure of an evaluation of collision risk is presented.

ミクロ交通シミュレーションによる交差点部の安全性評価に関する研究

A traffic safety measure is decided from the results of the traffic accident data. Therefore, it is difficult for us to decide the traffic safety measures and to do the previous evaluation for the traffic safety measures before a traffic accident occurs. In addition to this, we have the problem for implementing the suitable traffic safety measures when the traffic flow changed by modifying the road network and developing the new interchange. To solve this subject, we examined the micro-traffic simulation method (NETSIM and Simr) which is used the verification of traffic processing against the traffic safety evaluation. In consequence, we applied our past research results to the micro-traffic simulation and carried out developing the new safety evaluation technics of intersection.

An approach for auditing highway sections for safety improvements

The objective of this paper is to present a framework for the evaluation of traffic safety improvements on rural highways based on the existing process of the Ministry of Transportation of Ontario (MTO). The framework includes four steps to identify hazardous locations and determine the most feasible improvements. The framework was applied to a 2.2 km segment on Highway 17 (Ontario, Canada) to illustrate how the framework might be implemented in practice. The first step is defining the highway section to be studied. This section is usually a segment that was constructed in the same contract, and its surface conditions require major maintenance. The evaluation of traffic safety on sections that are undergoing major pavement rehabilitation will reduce the overall cost of road maintenance. The second step is to collect and analyze collision data, along with traffic and geometric data. The purpose of this step is to compare the actual number of collisions on the section with the expected long-run mean value and identify the causes of collisions. Based on this analysis, the third step identifies the possible improvements that would eliminate or minimize the number of collisions. These improvements can be as simple as signing improvement or as complex as a major realignment. Finally, these improvements are evaluated economically and environmentally. For this study, several sections of the Ministry of Transportation of Ontario, other ministries and levels of government, and interest groups participated in the evaluation process. A refined MTO process, currently being considered for implementation, is briefly described along with a discussion of its key features.Key words: evaluation, highway improvements, safety, three-dimensional alignments, sight distance, collision frequency.

A fuzzy set approach for bridge traffic safety evaluation1

Abstract On the basis of an extensive literature survey a set of factors that affect traffic safety on bridges was identified. These were grouped into three categories: bridge related, approach roadway related and environmentally related. A detailed accident analysis of a selected number of bridges in the state highway system of Indiana was conducted to verify these factors and to obtain insights into bridge accidents. A bridge traffic safety evaluation model was developed based on fuzzy set mathematics and the concept of linguistic variables. All subjective evaluations in the model are represented as fuzzy sets which are then considered as fuzzy numbers for the purpose of calculations. The weighted averages for the fuzzy weights and fuzzy ratings are calculated for each group of contributing factors. These weighted averages are then logically combined to obtain the Bridge Safety Index. The model takes into consideration the cumulative effect of the three groups of contributing factors related to bridge, approach roadway and environmental conditions. The resulting index, which is in the form of a fuzzy set, is transformed into the closest fuzzy number to represent the degree of bridge safety.

The state of Washington youth seat belt awareness program: An evaluation of two seat belt teaching kits : R. Pollack and F. Swant, Traffic Safety Evaluation Research Review, Spring 1983, 2(1), 11–24.

The Youth Seat Belt Awareness Program (YSBAP) was designed to increase seat belt usage among second grade students by presenting them with materials from the Adventures of Beltman or Buckle Up Box (BUB) seat belt teaching kits. Second grade classes in 510 elementary grade schools throughout the State of Washington were issued one of the seat belt teaching kits. The 510 schools were randomly divided into treatment or control conditions. Surveys were distributed to the students for their parent(s) to complete. The survey assessed parent-reported seat belt use for their second grader. The assessment of use was conducted prior to (PR), immediately following (P1), and 6 to 10 weeks after (P2) the students were exposed to the seat belt teaching materials. Analysis revealed a significant difference between the urban and rural counties for the control groups' reported usage rates. The urban counties control group usage rate was significantly greater than that of the rural counties control group at each survey phase. In view of these differences, analyses for treatment effects were conducted within county types. For the urban counties only, the BUB group had a reported usage percentage (immediately following presentation of the materials) significantly greater than the control group. For the rural counties, both the Beltman and BUB groups has significantly higher percentages of parent-reported seat belt use than the control groups had. This finding held for both the immediate (P1) and delayed (P2) survey assessment phases.

The Effect of Minimum Drinking Age Legislation on Youthful Auto Fatalities, 1970-1977

Annual state data on auto fatality rates for an 8-year period (1970-77) are examined to study the influence the magnitude of change in a state's minimum legal drinking age (mlda) has on teenage auto fatality rates. Factors taken into account include: the average auto fatality rate prior to the change; the year-to-year variability in this rate; the precise nature of the legal change; and minimum drinking age laws in contiguous states. During the 8-year period there were 20 instances in which a state reduced its mlda and one instance in which the mlda was increased. The principal finding is that a reduction in the mlda from 21 to 18 years of age for all alcoholic beverage types will result in an increase in the auto fatality rate for 18-to 20-year-olds of about 7 percent, and a somewhat smaller increase for 16-to 17-year-olds. It is estimated that the national 18-to 20-year-old auto fatality rate was about 3 percent higher in the mid-1970s than it would have been if minimum age laws had not been amended between 1970 and 1975. This information can serve as one useful input into the policy decision concerning the appropriate minimum drinking age. (Author/TRRL)

Traffic Safety of Older Drivers in Various Types of Road Intersections

In industrialized countries people over 50 years of age represent a rapidly growing part of population. Their lifestyle is also becoming more active, which means that the percentage of older drivers in the population of all drivers is also increasing. Many different studies have shown that elderly drivers are more frequently involved in specific types of accidents, especially at intersections. In the past 15 years there was a trend of increasing popularity of roundabouts in Slovenia. Their introduction was generally supported by the arguments of increased traffic-flow capacity and traffic safety as well. The studies on which these arguments are based were performed with an “ideal” type of driver in mind; the one that fully understands new rules and reacts correctly in all situations that may occur at such intersections, where there are no light signals to guide them. An elderly person does not necessarily conform to that ideal and if the percentage of elderly drivers became significant, the premises of the above mentioned studies may not be correct anymore which in turn implies that their results could also be questioned. The present study concentrated on the evaluation of traffic safety of elderly drivers, at various types of intersection, from their own perspective. Various statistical analyses of obtained data were performed. The most important finding was that we may claim, with high degree of probability, that the average person of the age of over 60 feels more unsafe at double-lane roundabouts than they would feel had the same intersection been equipped with traffic lights. Elderly traffic participants will always cause more accidents or participate in them due to hazardous factors. Challenge, arising from many different studies and researches, is in studying what measures and solutions can reduce the risk for elderly participants. KEYWORDS: traffic safety, road intersections, roundabouts, elderly people, older drivers