Effect of bus size and operation to crash occurrences

This paper evaluates roadway and operational factors considered to influence crashes involving buses. Factors evaluated included those related to bus sizes and operation services. Negative binomial (NB) and multinomial logit (MNL) models were used in linearizing and quantifying these factors with respect to crash frequency and injury severities, respectively. The results showed that position of the bus travel lane, presence or absence of on-street shoulder parking, posted speed limit, lane width, median width, number of lanes per direction and number of vehicles per lane has a higher influence on bus crashes compared to other roadway and traffic factors. Wider lanes and medians were found to reduce probability of bus crashes while more lanes and higher volume per lane were found to increase the likelihood of occurrences of bus-related crashes. Roadways with higher posted speed limits excluding freeways were found to have high probability of crashes compared to low speed limit roadways. Buses traveling on the inner lanes and making left turns were found to have higher probability of crashes compared to those traveling on the right most lanes. The same factors were found to influence injury severity though with varying magnitudes compared to crash frequency.     

The effect of infrastructure and demographic change on traffic-related fatalities and crashes: a case study of Illinois county-level data

This paper presents analyses of data from the Highway Safety Information System (HSIS) for the State of Illinois. Our analyses focuses on whether various changes in road network infrastructure and geometric design can be associated with changes in road fatalities and reported accidents. We also evaluate models that control for demographic changes. County-level time-series data is used and fixed effect negative binomial models are estimated. Results cannot confirm the hypothesis that changes in road infrastructure and geometric design have been beneficial for safety. Increases in the number of lanes appears to be associated with both increased traffic-related accidents and fatalities. Increased lane widths appears to be associated with increased fatalities. Increases in outside shoulder width appear to be associated with a decrease in accidents. Inclusion of demographic results does not significantly change these results but does capture much of the residual time trend in the models. Potentially mis-leading results are found when the time trend is not included. In this case a negative association between vertical curvature and both accidents and fatalities. No statistical association with changes in safety is found for median widths, inside shoulder widths, and horizontal and vertical curvature.     

Development of crash modification factors for changing lane width on roadway segments using generalized nonlinear models

This study evaluates the effectiveness of changing lane width in reducing crashes on roadway segments. To consider nonlinear relationships between crash rate and lane width, the study develops generalized nonlinear models (GNMs) using 3-years crash records and road geometry data collected for all roadway segments in Florida. The study also estimates various crash modification factors (CMFs) for different ranges of lane width based on the results of the GNMs. It was found that the crash rate was highest for 12-ft lane and lower for the lane width less than or greater than 12 ft. GNMs can extrapolate this nonlinear continuous effect of lane width and estimate the CMFs for any lane width, not only selected lane widths, unlike generalized linear models (GLMs) with categorical variables. The CMFs estimated using GNMs reflect that crashes are less likely to occur for narrower lanes if the lane width is less than 12 ft whereas crashes are less likely to occur for wider lanes if the lane width is greater than 12 ft. However, these effects varied with the posted speed limits as the effect of interaction between lane width and speed limit was significant. The estimated CMFs show that crashes are less likely to occur for lane widths less than 12 ft than the lane widths greater than 12 ft if the speed limit is higher than or equal to 40 mph. It was also found from the CMFs that crashes at higher severity levels (KABC and KAB) are less likely to occur for lane widths greater or less than 12 ft compared to 12-ft lane. The study demonstrates that the CMFs estimated using GNMs clearly reflect variations in crashes with lane width, which cannot be captured by the CMFs estimated using GLMs. Thus, it is recommended that if the relationship between crash rate and lane width is nonlinear, the CMFs are estimated using GNMs.     

Predicting the frequency of median barrier crashes on Pennsylvania interstate highways

Median barrier warrant criteria were developed in the 1970s and generally remain unchanged today. Vehicle travel, including both traffic volumes and operating speeds, have increased over this same time period. Encroachments into the median, and subsequent collisions with vehicles traveling in the opposite travel lanes, result in high severity crashes. Median barrier is typically used to prevent cross-median crashes; median barrier selection is based on median width and traffic volumes. Quantifiable information regarding the effects of median barrier installation and its placement on crash frequency is limited. This paper investigates median barrier crash frequency on Pennsylvania Interstate highways, including separate models for the Turnpike and all other Interstate-designated highways. Negative binomial regression models were used to develop predictive crash frequency tools. Traffic volume, horizontal alignment, interchange ramp presence, and median barrier offset distance from the travel lanes were used to estimate median barrier crash frequency. The analytical methodology developed in this research can be used, in concert with other prediction models, to assess the consequences of median barrier placement decisions.     

Powered two-wheeler drivers’ crash risk associated with the use of bus lanes

Context

Authorizing powered two-wheeler drivers to drive in lanes reserved to buses is a measure that is sometimes mentioned to improve mobility conditions for these users. But what effect would this measure have on the safety of these users and on the safety of the other users with whom they share the traffic space?

Objective

The objective of this study is to contribute elements to help answer this question. More precisely, the objective is to estimate the risk of having an accident per kilometer driven by powered two-wheeler drivers who drive in bus lanes and to compare this risk with that of powered two-wheeler drivers who drive in general traffic lanes.

Method

Using the bodily injury accidents recorded by the police over two years on 13 roads in the city of Marseille and a campaign of periodical observations of powered two-wheeler traffic, we estimated the risk per kilometer driven by powered two-wheeler drivers who drive in bus lanes and compared it with that of drivers who do not drive in them.

Results

The results show that the risk for powered two-wheeler drivers who drive in bus lanes of being involved in a bodily injury accident is significantly higher than the risk run by drivers who drive in general traffic lanes. For the 13 roads studied, it is on average 3.25 times higher (95% CI: 2.03; 5.21).

Conclusion

In the current situation, powered two-wheeler drivers who drive in bus lanes are less safe than those who drive in general traffic lanes. The analysis of police reports suggests that part of this increased risk comes from collisions between automobile drivers turning right and powered two-wheelers driving in the bus lane who continue straight ahead.     

Effect of shoulder width,guardrail and roadway geometry on driver perception and behavior

Roadway design is one of the most significant factors that affect driving behavior and perceived safety. The current study tests the combined effects of three roadway design elements – shoulders width, guardrail existence and roadway geometry (curvature) – on objective driving measures (speed and lane position), and subjective measures (perceived safe driving speed and estimated road safety).Twenty two drivers participated in an experiment with a driving simulation. In the first part objective driving data were collected, and in the second part subjective paper–pencil evaluations were requested of the perceived safety of 30 different scenarios that were previously experienced in the simulator. The scenarios consisted of the various combinations of the three roadway design elements.The results showed a significant effect of roadway geometry on both objective and subjective measures. The shoulders width had a significant effect on actual speed, on lane position, and on perceived safe driving speed, but only when a guardrail was present.These findings illustrate the perceptual role of a guardrail in defining the perceived safety margins that various shoulder widths provide. When a guardrail is absent, the width of the shoulder loses much of its benefits and effects on driving behavior. The results also demonstrate that roadway geometry can be used to reduce driving speeds, but at the same time it can have a negative effect on maintaining a stable lane position in sharp curves. Thus, controlling the width of road shoulders and the placement of guardrails seems to be a safer approach to speed and lane position control.     

Effect of shoulder width, guardrail and roadway geometry on driver perception and behavior

Roadway design is one of the most significant factors that affect driving behavior and perceived safety. The current study tests the combined effects of three roadway design elements – shoulders width, guardrail existence and roadway geometry (curvature) – on objective driving measures (speed and lane position), and subjective measures (perceived safe driving speed and estimated road safety).Twenty two drivers participated in an experiment with a driving simulation. In the first part objective driving data were collected, and in the second part subjective paper–pencil evaluations were requested of the perceived safety of 30 different scenarios that were previously experienced in the simulator. The scenarios consisted of the various combinations of the three roadway design elements.The results showed a significant effect of roadway geometry on both objective and subjective measures. The shoulders width had a significant effect on actual speed, on lane position, and on perceived safe driving speed, but only when a guardrail was present.These findings illustrate the perceptual role of a guardrail in defining the perceived safety margins that various shoulder widths provide. When a guardrail is absent, the width of the shoulder loses much of its benefits and effects on driving behavior. The results also demonstrate that roadway geometry can be used to reduce driving speeds, but at the same time it can have a negative effect on maintaining a stable lane position in sharp curves. Thus, controlling the width of road shoulders and the placement of guardrails seems to be a safer approach to speed and lane position control.     

Do accident-involved drivers exhibit riskier everyday driving behavior?

For more than forty years researchers have tried to relate traffic accident involvement to how an individual normally drives. Such efforts have not hitherto discovered clear effects. This study establishes statistically significant relations between prior involvement in accidents and an observed characteristic of every day driving. The observed driving characteristic is following headway in high flow freeway traffic, defined as the time interval between a vehicle and the preceding vehicle in the same lane. This headway is interpreted as a measure of driver risk. It is found that accident-involved drivers are more likely to follow with short headways (less than 1 s) than accident-free drivers. A similar effect is found in comparing drivers with and without traffic violations.     

基于演化博弈论的可变导向车道设置策略研究

可变导向车道的设置，在提高道路通行效率的同时会造成驾驶人情绪紧张或者因不了解路况导致违规甚至发生事故，对交通系统的安全和稳定运行产生负面影响。以交管部门设置可变导向车道的策略选择为研究目标，结合驾驶人走可变导向车道时产生的紧张情绪损失等因素，构建交管部门−驾驶人群体两方博弈模型。采用演化博弈论的方法分析博弈双方选择行为演化和稳定策略，对系统中存在的5个演化均衡点进行分析，得到系统的3种理想稳定状态和相对应的参数条件，为交管部门设置可变导向车道进行策略选择提供理论支撑。     

Has the difference in accident patterns between male and female drivers changed between 1984 and 2000?

The motorcar accident pattern of culpable young (18-25 years old) and middle-aged (35-55 years old) male and female drivers was studied in Finland. The aim was to see whether the difference in accident patterns between males and females has remained constant or whether it has changed over a 16-year period. Two different sets of traffic accident data were used. The first set of data covered all motorcar accidents for which damages were paid between 1987 and 2000, a total of 140802 accidents. The second set of data covered all fatal motor vehicle accidents in Finland during the time period between 1984 and 2000, a total of 2401 accidents. The results are analysed and discussed in the framework of a four-level hierarchical model of driving behaviour [Keskinen, E., 1996. Why do young drivers have more accidents? In: Junge, F., Fahrerinnen (Eds.), Young Drivers (in German and in English). Berichte der Bundesanstalt für Strabetaenwesen, Mensch und Sicherheit, Heft M 52, Bergisch Gladbach, Germany; Hatakka, M., Keskinen, E., Gregersen, N.P., Glad, A., Hernetkoski, K., 2002. From control of the vehicle to personal self-control; broadening the perspectives to driver education. Transportation Res. Part F 5 (3), 201-215]. Female drivers had proportionally more accidents that were connected to vehicle manoeuvring and control of traffic situations, e.g. reversing and loss-of-control accidents in a sober state and when not speeding. Male drivers, and especially young male drivers, had proportionally more accidents connected to higher levels of driving behaviour like motives for driving and attitudes. Factors that characterised these accidents were speeding and alcohol consumption. Male drivers also had previous traffic offences more often than female drivers. The study concludes that the difference in accident patterns between male and female drivers has remained constant, i.e. the accident pattern of female drivers was as dissimilar to the accident pattern of male drivers in the year 2000 as in the middle of the 1980s.     

Highway accident severities and the mixed logit model: an exploratory empirical analysis

Many transportation agencies use accident frequencies, and statistical models of accidents frequencies, as a basis for prioritizing highway safety improvements. However, the use of accident severities in safety programming has been often been limited to the locational assessment of accident fatalities, with little or no emphasis being placed on the full severity distribution of accidents (property damage only, possible injury, injury)-which is needed to fully assess the benefits of competing safety-improvement projects. In this paper we demonstrate a modeling approach that can be used to better understand the injury-severity distributions of accidents on highway segments, and the effect that traffic, highway and weather characteristics have on these distributions. The approach we use allows for the possibility that estimated model parameters can vary randomly across roadway segments to account for unobserved effects potentially relating to roadway characteristics, environmental factors, and driver behavior. Using highway-injury data from Washington State, a mixed (random parameters) logit model is estimated. Estimation findings indicate that volume-related variables such as average daily traffic per lane, average daily truck traffic, truck percentage, interchanges per mile and weather effects such as snowfall are best modeled as random-parameters-while roadway characteristics such as the number of horizontal curves, number of grade breaks per mile and pavement friction are best modeled as fixed parameters. Our results show that the mixed logit model has considerable promise as a methodological tool in highway safety programming.     

Perception of the risk of an accident by young and older drivers

Young drivers are significantly overrepresented among all drivers involved in traffic accidents and fatalities. Excessive risk taking by young drivers appears to be largely responsible for this disproportionate involvement. This excessive risk taking could be due to being more willing to take risks than older drivers are, failing to perceive hazardous situations as being as dangerous as older drivers do or both causes. This paper reports the results of a study which attempted to determine whether misperception of risk could be an explanation for the high rates of traffic accidents among youth by testing whether young drivers perceive driving to be less hazardous than do older drivers. Three different methods of estimating the risk of accident involvement were used to compare risk estimates of young and older drivers. The methods included general questions about accident involvement, rating the riskiness of ten specific driving situations illustrated in still photographs, and rating the riskiness of fifteen videotaped driving situations. Young drivers perceived their own chances of an accident to be significantly lower than those of both their peers and older male drivers, while older male drivers saw their chances of accident involvement as comparable to those of their male peers and less than those of young male drivers. These findings lend support to the thesis that young male drivers are overrepresented in traffic accidents at least in part because they fail to perceive specific driving situations as being as risky as older drivers perceive them.     

Models relating traffic safety with road environment and traffic flows on arterial roads in Addis Ababa

This paper presents the study carried out to develop accident predictive models based on the data collected on arterial roads in Addis Ababa. Poisson and negative binomial regression methods were used to relate the discrete accident data with the road and traffic flow explanatory variables. Significant accident predictive models were found with a number of significant explanatory variables. The results show that the existing inadequate road infrastructure and poor road traffic operations are the potential contributors of this ever-growing challenge of the road transport in Addis Ababa. The results also indicate that improvements in roadway width, pedestrian facilities, and access management are effective in reducing road traffic accidents.     

A crash-prediction model for road tunnels

Considerable research has been carried out into open roads to establish relationships between crashes and traffic flow, geometry of infrastructure and environmental factors, whereas crash-prediction models for road tunnels, have rarely been investigated. In addition different results have been sometimes obtained regarding the effects of traffic and geometry on crashes in road tunnels. However, most research has focused on tunnels where traffic and geometric conditions, as well as driving behaviour, differ from those in Italy. Thus, in this paper crash prediction-models that had not yet been proposed for Italian road tunnels have been developed. For the purpose, a 4-year monitoring period extending from 2006 to 2009 was considered. The tunnels investigated are single-tube ones with unidirectional traffic. The Bivariate Negative Binomial regression model, jointly applied to non-severe crashes (accidents involving material-damage only) and severe crashes (fatal and injury accidents only), was used to model the frequency of accident occurrence. The year effect on severe crashes was also analyzed by the Random Effects Binomial regression model and the Negative Multinomial regression model. Regression parameters were estimated by the Maximum Likelihood Method. The Cumulative Residual Method was used to test the adequacy of the regression model through the range of annual average daily traffic per lane. The candidate set of variables was: tunnel length (L), annual average daily traffic per lane (AADT_L), percentage of trucks (%Tr), number of lanes (N_L), and the presence of a sidewalk. Both for non-severe crashes and severe crashes, prediction-models showed that significant variables are: L, AADT_L, %Tr, and N_L. A significant year effect consisting in a systematic reduction of severe crashes over time was also detected. The analysis developed in this paper appears to be useful for many applications such as the estimation of accident reductions due to improvement in existing tunnels and/or to modifications of traffic control systems, as well as for the prediction of accidents when different tunnel design options are compared.     

Multi-level Bayesian safety analysis with unprocessed Automatic Vehicle Identification data for an urban expressway

In traffic safety studies, crash frequency modeling of total crashes is the cornerstone before proceeding to more detailed safety evaluation. The relationship between crash occurrence and factors such as traffic flow and roadway geometric characteristics has been extensively explored for a better understanding of crash mechanisms. In this study, a multi-level Bayesian framework has been developed in an effort to identify the crash contributing factors on an urban expressway in the Central Florida area. Two types of traffic data from the Automatic Vehicle Identification system, which are the processed data capped at speed limit and the unprocessed data retaining the original speed were incorporated in the analysis along with road geometric information. The model framework was proposed to account for the hierarchical data structure and the heterogeneity among the traffic and roadway geometric data. Multi-level and random parameters models were constructed and compared with the Negative Binomial model under the Bayesian inference framework. Results showed that the unprocessed traffic data was superior. Both multi-level models and random parameters models outperformed the Negative Binomial model and the models with random parameters achieved the best model fitting. The contributing factors identified imply that on the urban expressway lower speed and higher speed variation could significantly increase the crash likelihood. Other geometric factors were significant including auxiliary lanes and horizontal curvature.     

Annual mileage, driving violations, and accident involvement in relation to drivers' sex, age, and level of education.

The paper presents results of some analyses on a Dutch database that contains disaggregated data on both the traffic system input variables of the driver population (characteristics of drivers, including their annual mileage) and the output variables of the driver population in terms of habitual driving behaviour (operationalised in number of fines) and accident involvement. Accidents increased as annual mileage increased. A relationship between violations and accidents turned out to exist in different classes of annual mileage. Moreover, multivariate analyses showed that--corrected for annual mileage--male and female drivers do not differ in accident involvement; younger drivers have the highest rate of accidents and level of education is not related to accident involvement.     

Sensitivity analysis of an accident prediction model by the fractional factorial method

Sensitivity analysis of a model can help us determine relative effects of model parameters on model results. In this study, the sensitivity of the accident prediction model proposed by Zegeer et al. [Zegeer, C.V., Reinfurt, D., Hummer, J., Herf, L., Hunter, W., 1987. Safety Effect of Cross-section Design for Two-lane Roads, vols. 1-2. Report FHWA-RD-87/008 and 009 Federal Highway Administration, Department of Transportation, USA] to its parameters was investigated by the fractional factorial analysis method. The reason for selecting this particular model is that it incorporates both traffic and road geometry parameters besides terrain characteristics. The evaluation of sensitivity analysis indicated that average daily traffic (ADT), lane width (W), width of paved shoulder (PA), median (H) and their interactions (i.e., ADT-W, ADT-PA and ADT-H) have significant effects on number of accidents. Based on the absolute value of parameter effects at the three- and two-standard deviation thresholds ADT was found to be of primary importance, while the remaining identified parameters seemed to be of secondary importance. This agrees with the fact that ADT is among the most effective parameters to determine road geometry and therefore, it is directly related to number of accidents. Overall, the fractional factorial method was found to be an efficient tool to examine the relative importance of the selected accident prediction model parameters.     

Pedestrians' crossing behaviors and safety at unmarked roadway in China

Pedestrians’ crossing out of crosswalks (unmarked roadway) contributed to many traffic accidents, but existing pedestrian studies mainly focus on crosswalk crossing in developed countries specifically. Field observation of 254 pedestrians at unmarked roadway in China showed that 65.7% of them did not look for vehicles after arriving at the curb. Those who did look and pay attention to the traffic did so for duration of time that followed an exponential distribution. Pedestrians preferred crossing actively in tentative ways rather than waiting passively. The waiting time at the curb, at the median, and at the roadway all followed exponential distributions. During crossing, all pedestrians looked at the oncoming vehicles. When interacting with these vehicles, 31.9% of them ran and 11.4% stepped backwards. Running pedestrians usually began running at the borderline rather than within the lanes. Pedestrians preferred safe to short paths and they crossed second half of the road with significantly higher speed. These behavioral patterns were rechecked at an additional site with 105 pedestrians and the results showed much accordance. In terms of safety, pedestrians who were middle aged, involved in bigger groups, looked at vehicles more often before crossing or interacted with buses rather than cars were safer while those running were more dangerous. Potential applications of these findings, including building accurate simulation models of pedestrians and education of drivers and pedestrians in developing countries were also discussed.     

Pedestrians’ crossing behaviors and safety at unmarked roadway in China

Pedestrians’ crossing out of crosswalks (unmarked roadway) contributed to many traffic accidents, but existing pedestrian studies mainly focus on crosswalk crossing in developed countries specifically. Field observation of 254 pedestrians at unmarked roadway in China showed that 65.7% of them did not look for vehicles after arriving at the curb. Those who did look and pay attention to the traffic did so for duration of time that followed an exponential distribution. Pedestrians preferred crossing actively in tentative ways rather than waiting passively. The waiting time at the curb, at the median, and at the roadway all followed exponential distributions. During crossing, all pedestrians looked at the oncoming vehicles. When interacting with these vehicles, 31.9% of them ran and 11.4% stepped backwards. Running pedestrians usually began running at the borderline rather than within the lanes. Pedestrians preferred safe to short paths and they crossed second half of the road with significantly higher speed. These behavioral patterns were rechecked at an additional site with 105 pedestrians and the results showed much accordance. In terms of safety, pedestrians who were middle aged, involved in bigger groups, looked at vehicles more often before crossing or interacted with buses rather than cars were safer while those running were more dangerous. Potential applications of these findings, including building accurate simulation models of pedestrians and education of drivers and pedestrians in developing countries were also discussed.