Safety effects of an extensive black spot treatment programme in Flanders-Belgium

Black spot management is a widely implemented measure to improve traffic safety. This study evaluates the safety effects of an extensive black spot programme that has been implemented in Flanders-Belgium. In total, around 800 black spots were selected, from which 134 locations, redesigned between 2004 and 2007, were included in this study. The adopted approach is an empirical Bayes before- and after study that accounts for effects of general trends and for the stochastic nature of crashes, including regression to the mean. Two different comparison groups were established. The analyses showed a decrease in the number of injury crashes of 24–27%, significant at the 1%-level. A separate analysis for crashes with serious or fatal injuries showed a decrease of 46–57%, also significant at the 1% level. The highest effects were found for the implementation of changes in the layout of priority controlled intersections and for the installation of traffic signals, which showed a decrease of respectively 42% and 35% in the number of injury crashes. Signalized intersections at which left-turn phasing was implemented resulted in a decrease of 22% in the number of injury crashes, changes in the layout leaded to a decrease of 11%. The conversion of intersections (both signalized and priority controlled) into roundabouts resulted in a decrease of 21% in injury crashes. The black spot programme generated a favourable effect on each of the road user categories (car occupants, moped riders, cyclists, motorcyclist, pedestrians and truck drivers).     

Determining the drivers' acceptance of EFTCD in highway work zones

Traffic safety is a major concern in the temporary one-lane, two-way highway work zones due to the increasing of construction and maintenance operations. To prevent rear-end crashes and to mitigate the severity of these crashes caused by the inattentive driving, the utilization of the Emergency Flasher Traffic Control Device (EFTCD) was under consideration by government agencies, in addition to existing temporary traffic control devices installed in the one-lane, two-way highway work zones. The EFTCD was a newly proposed traffic warning device implemented through the use of vehicles’ hazard warning flashers. The primary objective of the research project was to investigate the drivers’ acceptance of the proposed EFTCD by measuring the mean speed changes of vehicles with and without EFTCD and by evaluating the drivers’ opinions of the EFTCD using the survey method. Field experimental results revealed that the EFTCD effectively reduced the mean vehicle speeds in the upstream of two work zones. A slow speed is more likely to reduce the severity of a crash in work zones. In addition, survey results indicated that 60% of the drivers thought the EFTCD signified a need for speed reduction and 82% of drivers recommended the implementation of the EFTCD in one-lane, two-way work zones. These results provide the necessary scientific justifications for the government agencies to decide if the EFTCD should be implemented in the one-lane, two-way highway work zones to prevent rear-end crashes and to mitigate the severity of these crashes.     

Safety impact of Gateway Monuments

Gateway Monuments are free standing roadside structures or signage that communicate the name of a city, country or township to motorists. The placement of such monuments within state-controlled right-of-way is a relatively recent occurrence in California. As a result, the California Department of Transportation (Caltrans) initiated research to quantify the impacts that this type of signage may or may not have on crashes in their vicinity. To date, no specific research has examined the impact such features have on crashes. To determine whether these features impacted safety, the before–after study method using the Empirical Bayes technique was used, with reference groups and Safety Performance Functions adapted from existing studies, eliminating the need to calibrate new models. Results indicated that, on an individual basis, no deterioration in safety was observed at any monument site. When all sites were examined collectively (using two different scenarios), the calculated index of effectiveness values were 0.978 and 0.680, respectively, corresponding to 2.2% and 32.0% reductions in crashes. In addition to the EB method, naïve study methods (with and without AADT taken into account) were applied to the study data. Results (crash reductions) from these methods also showed that the presence of Gateway Monuments did not have negative impact on traffic safety. However, the use of EB technique should be very careful employed when adopting reference groups from different jurisdictions, as these may affect the validity of EB results. In light of these results, Caltrans may continue to participate in the Gateway Monument Program at its discretion with the knowledge that roadway safety is not impacted by monuments.     

An assessment of the skid resistance effect on traffic safety under wet-pavement conditions

Pavement-tire friction provides the grip that is required for maintaining vehicle control and for stopping in emergency situations. Statistically significant negative correlations of skid resistance values and wet-pavement accident rates have been found in previous research. Skid resistance measured with SCRIM and crash data from over 1750 km of two-lane rural roads in the Spanish National Road System were analyzed to determine the influence of pavement conditions on safety and to assess the effects of improving pavement friction on safety. Both wet- and dry-pavement crash rates presented a decreasing trend as skid resistance values increased. Thresholds in SCRIM coefficient values associated with significant decreases in wet-pavement crash rates were determined. Pavement friction improvement schemes were found to yield significant reductions in wet-pavement crash rates averaging 68%. The results confirm the importance of maintaining adequate levels of pavement friction to safeguard traffic safety as well as the potential of pavement friction improvement schemes to achieve significant crash reductions.     

Evaluation of the impacts of traffic states on crash risks on freeways

The primary objective of this study is to divide freeway traffic flow into different states, and to evaluate the safety performance associated with each state. Using traffic flow data and crash data collected from a northbound segment of the I-880 freeway in the state of California, United States, K-means clustering analysis was conducted to classify traffic flow into five different states. Conditional logistic regression models using case-controlled data were then developed to study the relationship between crash risks and traffic states. Traffic flow characteristics in each traffic state were compared to identify the underlying phenomena that made certain traffic states more hazardous than others. Crash risk models were also developed for different traffic states to identify how traffic flow characteristics such as speed and speed variance affected crash risks in different traffic states. The findings of this study demonstrate that the operations of freeway traffic can be divided into different states using traffic occupancy measured from nearby loop detector stations, and each traffic state can be assigned with a certain safety level. The impacts of traffic flow parameters on crash risks are different across different traffic flow states. A method based on discriminant analysis was further developed to identify traffic states given real-time freeway traffic flow data. Validation results showed that the method was of reasonably high accuracy for identifying freeway traffic states.     

Rating the overall secondary safety of vehicles from real world crash data: the Australian and New Zealand Total Secondary Safety Index

Various systems for rating secondary safety of particular makes and models of vehicles have been developed internationally. These measures generally evaluate crashworthiness (the ability of the vehicle to protect its own occupants in the event of a crash) separately from aggressivity (the harm a vehicle is liable to impose on other road users into which it crashes). This paper describes an approach using Australian and New Zealand data that combines these two facets of secondary safety into one ‘Total Secondary Safety Index’ estimated from real world crash outcomes. The Index estimates the risk of death or serious injury to all key road users in crashes involving light passenger vehicles across the full range of crash types. This paper describes the rationale and method for producing this Index, together with some estimates for common Australian and New Zealand makes and models of light passenger vehicles.     

Safety effects of reducing the speed limit from 90 km/h to 70 km/h

Speed is one of the main risk factors in traffic safety, as it increases both the chances and the severity of a crash. In order to achieve improved traffic safety by influencing the speed of travel, road authorities may decide to lower the legally imposed speed limits. In 2001 the Flemish government decided to lower speed limits from 90 km/h to 70 km/h on a considerable number of highways. The present study examines the effectiveness of this measure using a comparison group before- and after study to account for general trend effects in road safety. Sixty-one road sections with a total length of 116 km were included. The speed limits for those locations were restricted in 2001 and 2002. The comparison group consisted of 19 road sections with a total length of 53 km and an unchanged speed limit of 90 km/h throughout the research period. Taking trend into account, the analyses showed a 5% decrease [0.88; 1.03] in the crash rates after the speed limit restriction. A greater effect was identified in the case of crashes involving serious injuries and fatalities, which showed a decrease of 33% [0.57; 0.79]. Separate analyses between crashes at intersections and at road sections showed a higher effectiveness at road sections. It can be concluded from this study that speed limit restrictions do have a favorable effect on traffic safety, especially on severe crashes. Future research should examine the cause for the difference in the effect between road sections and intersections that was identified, taking vehicle speeds into account.     

Automated section speed control on motorways: An evaluation of the effect on driving speed

Automated section speed control is a fairly new traffic safety measure that is increasingly applied to enforce speed limits. The advantage of this enforcement system is the registration of the average speed at an entire section, which would lead to high speed limit compliances and subsequently to a reduction in the vehicle speed variability, increased headway, more homogenised traffic flow and increased traffic capacity. However, the number of studies that analysed these effects are limited. The present study evaluates the speed effect of two section speed control systems in Flanders, Belgium. Both sections are located in the opposite direction of a three-lane motorway with a posted speed limit of 120 km/h. Speed data were collected at different points: from 6 km before the entrance of the section to 6 km downstream from the section. The effect was analysed through a before- and after comparison of travel speeds. General time trends and fluctuations were controlled through the analysis of speeds at comparison locations. On the enforced sections considerable decreases were found of about 5.84 km/h in the average speed, 74% in the odds of drivers exceeding the speed limit and 86% in the odds of drivers exceeding the speed limit by more than 10%. At the locations up- and downstream from the section also favourable effects were found for the three outcomes. Furthermore a decrease in the speed variability could be observed at all these data points.     

Evaluating the road safety effects of a fuel cost increase measure by means of zonal crash prediction modeling

Travel demand management (TDM) consists of a variety of policy measures that affect the transportation system's effectiveness by changing travel behavior. The primary objective to implement such TDM strategies is not to improve traffic safety, although their impact on traffic safety should not be neglected. The main purpose of this study is to evaluate the traffic safety impact of conducting a fuel-cost increase scenario (i.e. increasing the fuel price by 20%) in Flanders, Belgium. Since TDM strategies are usually conducted at an aggregate level, crash prediction models (CPMs) should also be developed at a geographically aggregated level. Therefore zonal crash prediction models (ZCPMs) are considered to present the association between observed crashes in each zone and a set of predictor variables. To this end, an activity-based transportation model framework is applied to produce exposure metrics which will be used in prediction models. This allows us to conduct a more detailed and reliable assessment while TDM strategies are inherently modeled in the activity-based models unlike traditional models in which the impact of TDM strategies are assumed. The crash data used in this study consist of fatal and injury crashes observed between 2004 and 2007. The network and socio-demographic variables are also collected from other sources. In this study, different ZCPMs are developed to predict the number of injury crashes (NOCs) (disaggregated by different severity levels and crash types) for both the null and the fuel-cost increase scenario. The results show a considerable traffic safety benefit of conducting the fuel-cost increase scenario apart from its impact on the reduction of the total vehicle kilometers traveled (VKT). A 20% increase in fuel price is predicted to reduce the annual VKT by 5.02 billion (11.57% of the total annual VKT in Flanders), which causes the total NOCs to decline by 2.83%.     

Assessment of safety effects for widening urban roadways in developing crash modification functions using nonlinearizing link functions

Since a crash modification factor (CMF) represents the overall safety performance of specific treatments in a single fixed value, there is a need to explore the variation of CMFs with different roadway characteristics among treated sites over time. Therefore, in this study, we (1) evaluate the safety performance of a sample of urban four-lane roadway segments that have been widened with one through lane in each direction and (2) determine the relationship between the safety effects and different roadway characteristics over time. Observational before–after analysis with the empirical Bayes (EB) method was assessed in this study to evaluate the safety effects of widening urban four-lane roadways to six-lanes. Moreover, the nonlinearizing link functions were utilized to achieve better performance of crash modification functions (CMFunctions). The CMFunctions were developed using a Bayesian regression method including the estimated nonlinearizing link function to incorporate the changes in safety effects of the treatment over time. Data was collected for urban arterials in Florida, and the Florida-specific full SPFs were developed and used for EB estimation.     

Safety climate and self-reported injury: assessing the mediating role of employee safety control

To further reduce injuries in the workplace, companies have begun focusing on organizational factors which may contribute to workplace safety. Safety climate is an organizational factor commonly cited as a predictor of injury occurrence. Characterized by the shared perceptions of employees, safety climate can be viewed as a snapshot of the prevailing state of safety in the organization at a discrete point in time. However, few studies have elaborated plausible mechanisms through which safety climate likely influences injury occurrence. A mediating model is proposed to link safety climate (i.e., management commitment to safety, return-to-work policies, post-injury administration, and safety training) with self-reported injury through employees' perceived control on safety. Factorial evidence substantiated that management commitment to safety, return-to-work policies, post-injury administration, and safety training are important dimensions of safety climate. In addition, the data support that safety climate is a critical factor predicting the history of a self-reported occupational injury, and that employee safety control mediates the relationship between safety climate and occupational injury. These findings highlight the importance of incorporating organizational factors and workers' characteristics in efforts to improve organizational safety performance.     

Limits of the quasi-induced exposure method when compared with the standard case-control design. Application to the estimation of risks associated with driving under the influence of cannabis or alcohol

The disparities between the quasi-induced exposure (QIE) method and a standard case–control approach with crash responsibility as disease of interest are studied. The 10,748 drivers who had been given compulsory cannabis and alcohol tests subsequent to involvement in a fatal crash in France between 2001 and 2003 were used to compare the two approaches. Odds ratios were assessed using conditional and unconditional logistic regressions. While both approaches found that drivers under the influence of alcohol or cannabis increased the risk of causing a fatal crash, the two approaches are not equivalent. They differ mainly with regards to the driver sample selected. The QIE method results in splitting the overall road safety issue into two sub-studies: a matched case–control study dealing with two-vehicle crashes and a case–control study dealing with single-vehicle crashes but with a specific control group. Using a specific generic term such as “QIE method” should not hide the real underlying epidemiological design. On the contrary, the standard case–control approach studies drivers involved in all type of crashes whatever the distribution of the responsibility in each crash. This method also known as “responsibility analysis” is the most relevant for assessing the overall road safety implications of a driver characteristic.     

Developing crash modification functions to assess safety effects of adding bike lanes for urban arterials with different roadway and socio-economic characteristics

Although many researchers have estimated crash modification factors (CMFs) for specific treatments (or countermeasures), there is a lack of studies that explored the heterogeneous effects of roadway characteristics on crash frequency among treated sites. Generally, the CMF estimated by before–after studies represents overall safety effects of the treatment in a fixed value. However, as each treated site has different roadway characteristics, there is a need to assess the variation of CMFs among the treated sites with different roadway characteristics through crash modification functions (CMFunctions). The main objective of this research is to determine relationships between the safety effects of adding a bike lane and the roadway characteristics through (1) evaluation of CMFs for adding a bike lane using observational before–after with empirical Bayes (EB) and cross-sectional methods, and (2) development of simple and full CMFunctions which are describe the CMF in a function of roadway characteristics of the sites. Data was collected for urban arterials in Florida, and the Florida-specific full SPFs were developed. Moreover, socio-economic parameters were collected and included in CMFunctions and SPFs (1) to capture the effects of the variables that represent volume of bicyclists and (2) to identify general relationship between the CMFs and these characteristics. In order to achieve better performance of CMFunctions, data mining techniques were used.     

Safety impacts due to the incompatibility of SUVs, minivans, and pickup trucks in two-vehicle collisions

This research sets out to estimate the effects of vehicle incompatibility on the risk of death or major injury to drivers involved in two-vehicle collisions.Based on data for 2,999,395 drivers, logistic regression was used to model the risk of driver death or major injury (defined has being hospitalized). Our analyses show that pickup trucks, minivans and sport utility vehicles (SUVs) are more aggressive than cars for the driver of the other vehicle and more protective for their own drivers. The effect of the pickups is more pronounced in terms of aggressivity. The point estimates are comparable to those in the Toy and Hammitt study [Toy, E.L., Hammitt, J.K., 2003. Safety impacts of SUVs, minivans, and pickup trucks in two-vehicle crashes. Risk Analysis 23, 641–650], but, in contrast to that study, we are now able to establish that a greater number of these effects are statistically significant with a larger sample size.Like vehicle mass and type, other characteristics of drivers and the circumstances of the collision influence the driver’s condition after impact. Male drivers, older drivers, drivers who are not wearing safety belts, collisions occurring in a higher speed zone and head-on collisions significantly increase the risk of death. Except for the driver’s sex, all of these categories are also associated with an increased risk of death or of being hospitalized after being involved in a two-vehicle collision. For this risk, a significant increase is associated with female drivers.     

Examining the effects of site selection criteria for evaluating the effectiveness of traffic safety countermeasures

The primary objective of this paper is to describe how site selection effects can influence the safety effectiveness of treatments. More specifically, the goal is to quantify the bias for the safety effectiveness of a treatment as a function of different entry criteria as well as other factors associated with crash data, and propose a new method to minimize this bias when a control group is not available. The study objective was accomplished using simulated data. The proposed method documented in this paper was compared to the four most common types of before–after studies: the Naïve, using a control group (CG), the empirical Bayes (EB) method based on the method of moment (EB_MM), and the EB method based on a control group (EB_CG). Five scenarios were examined: a direct comparison of the methods, different dispersion parameter values of the Negative Binomial model, different sample sizes, different values of the index of safety effectiveness (θ$\theta$), and different levels of uncertainty associated with the index. Based on the simulated scenarios (also supported theoretically), the study results showed that higher entry criteria, larger values of the safety effectiveness, and smaller dispersion parameter values will cause a larger selection bias. Furthermore, among all methods evaluated, the Naïve and the EB_MM methods are both significantly affected by the selection bias. Using a control group, or the EB_CG, can mutually eliminate the site selection bias, as long as the characteristics of the control group (truncated data for the CG method or the non-truncated sample population for the EB_CG method) are exactly the same as for the treatment group. In practice, finding datasets for the control group with the exact same characteristics as for the treatment group may not always be feasible. To overcome this problem, the method proposed in this study can be used to adjust the Naïve estimator of the index of safety effectiveness, even when the mean and dispersion parameter are not properly estimated.     

Assessing the safety effects of multiple roadside treatments using parametric and nonparametric approaches

This study evaluates the safety effectiveness of multiple roadside elements on roadway segments by estimating crash modification factors (CMFs) using the cross-sectional method. To consider the nonlinearity in crash predictors, the study develops generalized nonlinear models (GNMs) and multivariate adaptive regression splines (MARS) models. The MARS is one of the promising data mining techniques due to its ability to consider the interaction impact of more than one variables and nonlinearity of predictors simultaneously. The CMFs were developed for four roadside elements (driveway density, poles density, distance to poles, and distance to trees) and combined safety effects of multiple treatments were interpreted by the interaction terms from the MARS models. Five years of crash data from 2008 to 2012 were collected for rural undivided four-lane roadways in Florida for different crash types and severity levels. The results show that the safety effects decrease as density of driveways and roadside poles increase. The estimated CMFs also indicate that increasing distance to roadside poles and trees reduces crashes. The study demonstrates that the GNMs show slightly better model fitness than negative binomial (NB) models. Moreover, the MARS models outperformed NB and GNM models due to its strength to reflect the nonlinearity of crash predictors and interaction impacts among variables under different ranges. Therefore, it can be recommended that the CMFs are estimated using MARS when there are nonlinear relationships between crash rate and roadway characteristics, and interaction impacts among multiple treatments.     

危险化学品安全管控与应急救援

危险是危险化学品的天然特征,安全是危险化学品永恒的主题。每一次危险化学品的安全事故,既是其本质特征使然,也与外部环境密切相关,往往在其偶发性中包含着必然性。只有在充分了解、掌握其本质特征基础上,合理设置外部条件,使其始终处于可控的安全状态,并做好安全管控和应急救援的各项准备工作,才是保障安全、防控灾害的根本方法。血的教训不可忘,要想悲剧不再重演,必须采用系统思维进行体系建设,利用先进信息通讯技术采用"互联网+"模式建立全国统一的全天候的实时动态监控体系,在规范管理、防患未然的同时,为应急救援工作提供准确信息和合理救援方案。     

危险化学品安全管控与应急救援

危险是危险化学品的天然特征,安全是危险化学品永恒的主题。每一次危险化学品的安全事故,既是其本质特征使然,也与外部环境密切相关,往往在其偶发性中包含着必然性。只有在充分了解、掌握其本质特征基础上,合理设置外部条件,使其始终处于可控的安全状态,并做好安全管控和应急救援的各项准备工作,才是保障安全、防控灾害的根本方法。血的教训不可忘,要想悲剧不再重演,必须采用系统思维进行体系建设,利用先进信息通讯技术采用"互联网+"模式建立全国统一的全天候的实时动态监控体系,在规范管理、防患未然的同时,为应急救援工作提供准确信息和合理救援方案。     

浅谈加气站车载气瓶充装安全双体系建设

安全生产风险分级管控和事故隐患排查治理双重预防体系(简称双体系)自2016年开始建设以来在化工、特种设备等行业得到了较快的应用与发展。特种设备作为对人类生命财产安全具有重大威胁的设备种类,其双体系的建立就显得尤为重要。加气站作为车载气瓶充装的经营单位,特种设备主要有LNG储罐、CNG储气瓶组和压力管道等。作为CNG和LNG的充装单位,储存有大量的CNG和LNG,并且时常进行CNG和LNG的车载气瓶充装,其危险程度不言而喻,所以建立特种设备双体系显得尤为重要。文章以车载气瓶充装为主体,对双体系的建设过程进行了介绍和分析,通过双体系的运行情况结合发现的问题进行了总结。通过双体系的建立和运行,切实减少了加气站在管理和使用过程中的安全隐患,对加气站的安全管理和安全保障具有重大意义。     

果蔬及肉类冷链食品在流通过程中的安全控制

果蔬及肉类冷链食品在贮藏、运输和销售的流通过程中要经过众多的环节,并与人手、各种工具及空气有许多接触,很容易受到微生物和尘土的污染,出现腐烂、变质等食品安全问题。针对不同食品的要求,采用合适的包装,控制好适宜的温度并保持冷链的连续性及温度的稳定性,可以最大限度地减少食品在流通过程中的腐烂变质,减少损失,确保食品的质量安全。