Analytic Methods in Accident Research最新文献

{"title":"Evaluating the safety of autonomous vehicle–pedestrian interactions: An extreme value theory approach","authors":"Abdul Razak Alozi,&nbsp;Mohamed Hussein","doi":"10.1016/j.amar.2022.100230","DOIUrl":"10.1016/j.amar.2022.100230","url":null,"abstract":"<div><p>With the increasing advancements in autonomous vehicle (AV) technologies, the forecasts of AV market shares seem to follow an ever-growing trend. This leads to the inherent need for proactive safety evaluations of AV impacts on other road users. To that end, this study proposes a modeling framework for the proactive assessment of pedestrian safety in AV environments. The proposed framework relies on the Extreme Value Theory (EVT), with the peak over threshold modeling technique, to develop an estimate of AV-pedestrian collisions using AV-pedestrian conflicts. The proposed framework was applied to two AV datasets, collected from three locations in the US and Singapore, using the operating AV fleets of two developers, Motional and Lyft. Both datasets included trajectory data for the subject AV, as well as LiDAR point clouds and annotated video data from AV cameras to capture the trajectories of surrounding road users. The datasets were processed to extract the AV-pedestrian conflicts along with the corresponding conflict indicators, mainly the post-encroachment time (PET) and time-to-collision (TTC). Relevant covariates were introduced to the proposed models to enhance their performance and prediction accuracy, including turning movements and conflict speeds. The results indicate an alarming risk to pedestrians when interacting with AVs, especially at the early stages of AV adoption. The expected number of collisions ranged from 4 to 5.5 per million vehicle kilometers travelled (VKT) of the AVs. With the addition of the covariates, the expected number of collisions went down to a range of 2.3–3.7 per million VKT, but with a narrower confidence interval of the resulting estimate and a better fit. The introduced approach shows promising prospects for the application of EVT methods to address AV safety impacts. It also invites future applications to address issues of concern for pedestrian safety in different conditions of urban traffic.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"35 ","pages":"Article 100230"},"PeriodicalIF":12.9,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48290211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The impact of weekday, weekend, and holiday crashes on motorcyclist injury severities: accounting for temporal influence with unobserved effect and insight from out-of-sample prediction","authors":"Chamroeun Se, Thanapong Champahom, Sajjakaj Jomnonkwao, N. Kronprasert, V. Ratanavaraha","doi":"10.1016/j.amar.2022.100240","DOIUrl":"https://doi.org/10.1016/j.amar.2022.100240","url":null,"abstract":"","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":" ","pages":""},"PeriodicalIF":12.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48729408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A deep generative approach for crash frequency model with heterogeneous imbalanced data","authors":"Hongliang Ding ,&nbsp;Yuhuan Lu ,&nbsp;N.N. Sze ,&nbsp;Tiantian Chen ,&nbsp;Yanyong Guo ,&nbsp;Qinghai Lin","doi":"10.1016/j.amar.2022.100212","DOIUrl":"10.1016/j.amar.2022.100212","url":null,"abstract":"<div><p>Crash frequency model is often subject to excessive zero observation because of the rare nature of crashes. To address the problem of imbalanced crash data, a deep generative approach – augmented variational autoencoder – was proposed to generate synthetic crash data for the association measure between crash and possible explanatory factors. This approach was characterized by a factorized generative model and refined objective function. For instance, the generative model can handle heterogeneous data including real-valued, nominal and ordinal distributions. On the other hand, the refined objective function can control for the random effect by better recognizing both the zero-crash and non-zero crash cases. In this study, comprehensive traffic and crash data of multiple distribution types in Hong Kong in the period between 2014 and 2016 were used. To assess the data generation performance of the proposed augmented variational autoencoder method, a conventional data synthesis technique (synthetic minority oversampling technique-nominal continuous) was also considered. Performances of crash frequency models of total crashes and fatal and severe injury crashes are assessed. For total crashes, the results of parameter estimation, in terms of statistical fit, prediction accuracy, and explanatory factors identified, of the crash frequency model based on synthetic data using the augmented variational autoencoder method adhered closer to that based on original data, compared to that based on synthetic data using the synthetic minority oversampling technique-nominal continuous method. For fatal and severe injury crashes, zero-crash observations were prevalent, with the ratio of zero-crash to non-zero crash cases of 9 to 1. Crash data was first balanced using the proposed augmented variational autoencoder method. Then, fatal and severe injury crash frequency models using correlated random parameter models based on original data and balanced data were estimated respectively. Results indicate that fatal and severe injury crash frequency model based on balanced data outperforms its counterpart, with the lowest root mean square error, lowest mean absolute error, and highest number of crash explanatory factors identified. More importantly, correlation between the random parameters can be revealed. Findings of this study should shed light to both researchers and practitioners for the development of crash frequency models, with which the problem of excessive zero observations is prevalent when highly disaggregated traffic and crash data by time and space are used.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100212"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49094989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of higher speed limits on crash-injury severity rates: A correlated random parameters bivariate tobit approach","authors":"Sheikh Shahriar Ahmed ,&nbsp;Nawaf Alnawmasi ,&nbsp;Panagiotis Ch. Anastasopoulos ,&nbsp;Fred Mannering","doi":"10.1016/j.amar.2022.100213","DOIUrl":"10.1016/j.amar.2022.100213","url":null,"abstract":"<div><p>Over the last few decades, interstate speed limits in different US states have been increased from 70 mi/h to 75 mi/h or 80 mi/h, even to 85 mi/h in some instances. The implication of such speed limit increases on crash likelihoods and resulting injury severities is a key concern. To understand the impact of speed limit increases on no-injury and injury crash rates (including fatalities) multi-year segment-specific freeway crash data from the state of Kansas (including both pre-, and post-speed limit increase crash information) are modeled using a correlated random parameters bivariate tobit model. To address possible temporal variations in the effects of explanatory variables across years, year-specific models were estimated. Model estimation results indicate that several traffic, segment geometry, and pavement-specific characteristics affect no-injury and injury crash rates. From the year-specific model estimation results it was determined that the effects of the factors affecting pre- and post-speed limit crash rates did change significantly over time. However, such changes were also observed in the pre-speed limit increase years, as well as the post-speed limit increase years. While findings do suggest a small but statistically significant increase in injury crash rates after speed limits were raised, temporal changes in the effects of factors contributing to no-injury and injury crash rates make it difficult to isolate the true impacts of increased speed limits.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100213"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42186076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The impact of higher speed limits on the frequency and severity of freeway crashes: Accounting for temporal shifts and unobserved heterogeneity","authors":"Nawaf Alnawmasi ,&nbsp;Fred Mannering","doi":"10.1016/j.amar.2021.100205","DOIUrl":"10.1016/j.amar.2021.100205","url":null,"abstract":"<div><p>In recent years, US States have raised their maximum interstate speed limits from 70 mi/h to 75 mi/h, 80 mi/h and even 85 mi/h. However, understanding the effect that these higher speed limits have had on the frequency and severity of crashes using traditional before and after analyses has been difficult due to possible temporal shifts in driver behavior, and potential changes in vehicle safety technology and highway safety features. Using multi-year data from before and after higher speed limits were instituted on Kansas freeways, random parameters models of crash frequency and resulting injury severity were estimated. Regarding the frequency of crashes, the findings showed that the higher speed limits did not have a significant effect in the mean number of crashes on the 253 studied roadway segments. For injury severity, model-estimation results in one- and two-vehicle crashes show that the factors affecting driver-injury severities have changed before and after the speed limit increase, but changes were also observed in the years before the speed limit increases and the years after. However, using pre-speed-limit-increase model estimation results to predict post-speed-limit-increase injury-severity distributions it was found that the aggregate effect of the changing influences of explanatory variables on average injury severities was relatively small. While the injury-severity estimation results make it difficult to attribute any temporal shifts in parameter values to the increased speed limit, there was a significant increase in the probability of rollover crashes that suggests the higher speed limits may have had some contributory effect on injury severities in single-vehicle crashes.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100205"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47550429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A temporal assessment of distracted driving injury severities using alternate unobserved-heterogeneity modeling approaches","authors":"Nawaf Alnawmasi ,&nbsp;Fred Mannering","doi":"10.1016/j.amar.2022.100216","DOIUrl":"10.1016/j.amar.2022.100216","url":null,"abstract":"<div><p>This study explores temporal shifts in the effects of explanatory variables on the injury severity outcomes of crashes involving distracted driving. Using data from distracted driving crashes on Kansas State highways over a four-year period (from 2014 to 2017 inclusive), separate yearly models of driver-injury severities (with possible outcomes of severe injury, minor injury, and no injury) were estimated using two alternate modeling approaches to account for possible unobserved heterogeneity: a latent-class multinomial logit with class probability functions and a random parameters logit with possible heterogeneity in the means and variances of random parameters. Likelihood ratio tests were conducted to determine if model parameter estimates have shifted over time. A wide range of variables were found to statistically influence driver-injury severities and the findings show that were statistically significant temporal shifts in parameter estimates in both the random parameters and latent class modeling approaches. These shifts are likely the result of changes in driver behavior, improvements in vehicle and highway safety features, changes in communication technologies, and other temporally shifting trends. However, while out-of-sample simulations show that the two modeling approaches both indicate that distracted driving crashes have become less severe over time, the alternate approaches produced substantially different injury-severity predictions, suggesting the need for future research to explore how unobserved heterogeneity can best be modeled in temporal contexts.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100216"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41368542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal instability analysis of injury severities in truck-involved and non-truck-involved crashes","authors":"Chenzhu Wang ,&nbsp;Fei Chen ,&nbsp;Yunlong Zhang ,&nbsp;Jianchuan Cheng","doi":"10.1016/j.amar.2022.100214","DOIUrl":"10.1016/j.amar.2022.100214","url":null,"abstract":"<div><p>The truck involvement could potentially increase the crash frequency and resulted injury outcomes and it is of great necessity to understand the similarities and differences in the mechanism of how determinants influence injury severities of truck-involved and non-truck-involved crashes and explore their spatiotemporal stability. Based on the crash data of Beijing-Shanghai Expressway and Changchun-Shenzhen Expressway over the three years (2017–2019), the heterogeneity and spatiotemporal stability of contributing factors affecting truck-involved and non-truck-involved crashes were investigated through random-parameter logit models with unobserved heterogeneity in means and variances. Three injury severity outcomes of severe injury, minor injury, and no injury were examined considering multiple factors including driver, vehicle, roadway, environmental, temporal, spatial, traffic and crash characteristics. Besides, the spatiotemporal stability was investigated based on the likelihood ratio tests. Marginal effects were also calculated to analyze the spatiotemporal stability and potential heterogeneity of the contributing variables from year to year. The findings exhibited remarkable differences between truck-involved and non-truck-involved crashes, and an overall spatiotemporal instability was observed in the current study while several indicators were also reported to show relative spatial or temporal stability such as length of the horizontal curve, <em>AADT</em>, early morning, cloudy weather. This paper provided some suggestions to prevent crashes for truck-involved and non-truck-involved crashes across different highways respectively and develop safety measures accordingly.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100214"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47835237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bayesian dynamic extreme value modeling for conflict-based real-time safety analysis","authors":"Chuanyun Fu ,&nbsp;Tarek Sayed","doi":"10.1016/j.amar.2021.100204","DOIUrl":"10.1016/j.amar.2021.100204","url":null,"abstract":"<div><p>Real-time safety analysis and optimization using surrogate safety measures such as traffic conflicts and techniques such extreme value theory (EVT) models is an emerging research topic in the context of proactive traffic safety management. However, the predictive performance and temporal transferability of the existing real-time safety analysis EVT models are subject to the assumption of invariant model parameters, which do not account for the temporal variability and is not suitable for real-time traffic data analysis. This study proposes a Bayesian dynamic extreme value modeling approach for conflict-based real-time safety analysis which integrates a Bayesian dynamic linear model with the extreme value distribution. The proposed approach has several unique advantages as it: 1) allows the model parameters to be time-varying; 2) integrates the newer data with prior information to recursively update the model parameters and account for state-space changes and react to sudden trend changes; 3) accounts for temporal variability and non-stationarity in conflict extremes; and 4) quantitatively evaluates the real-time safety levels of a road facility. The proposed approach is applied for cycle-by-cycle safety analysis at four signalized intersections in the city of Surrey, British Columbia. Traffic conflicts are characterized by the modified time to collision indicator. Three traffic parameters (traffic volume, shock wave area, and platoon ratio) at the signal cycle level are considered as covariates to account for non-stationarity. Several Bayesian dynamic and static extreme value models are developed and two safety indices, namely risk of crash (RC) and return level (RL), are generated to quantitatively represent the cycle-level safety. The RC directly reflects whether a cycle is risky while the RL can evaluate the safety levels of individual cycles. The results show that the dynamic model can identify more crash-risk cycles with either a positive RC or a positive RL than the static model and is more capable of differentiating the safety levels for individual cycles in terms of RL. Overall, the dynamic model outperforms the static model in terms of the statistical fit and aggregate crash estimation accuracy.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100204"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49297670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A temporal instability analysis of environmental factors affecting accident occurrences during snow events: The random parameters hazard-based duration model with means and variances heterogeneity","authors":"Jiajun Pang ,&nbsp;Adam Krathaus ,&nbsp;Irina Benedyk ,&nbsp;Sheikh Shahriar Ahmed ,&nbsp;Panagiotis Ch. Anastasopoulos","doi":"10.1016/j.amar.2022.100215","DOIUrl":"10.1016/j.amar.2022.100215","url":null,"abstract":"<div><p><span>The present paper introduces the time between the start of a snowfall and the occurrence of a motor vehicle accident as a novel measure for evaluating motor vehicle safety during snowfalls. Detailed information of accidents that occurred during snowfalls between 2017 and 2020 in the state of New York are used to explore the accelerating or delaying effect of different factors on the time between the start of a snowfall and the occurrence of an accident. To that end, the hazard-based duration modeling framework is employed, and to account for multiple layers of unobserved heterogeneity, a random parameters with heterogeneity in means and variances approach is introduced – for this first time, to the authors’ knowledge. The temporal stability of the factors across the study period is investigated through conducting a series of systematic likelihood ratio tests, and the factors are not found to be temporally stable across the study years. Hence, separate year-specific models are estimated. The results show that a number of factors affect the time between the start of a snowfall and the occurrence of a motor vehicle accident such as: visibility conditions; concrete road sections; road sections with high </span>Pavement<span> Condition Index (PCI); roads with more than 4 lanes in both directions; locations in close proximity to bus stations; the period during the cold winter months (specifically February); the amount of accumulated snow on the ground before snowfall; the presence of ramps; and long time intervals between snowfalls (especially for heavy snow conditions and adverse visibility conditions). The findings from this paper are anticipated to offer insights to winter maintenance teams, transportation system operators, and users regarding accident-prone periods and locations during snowfalls.</span></p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"34 ","pages":"Article 100215"},"PeriodicalIF":12.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47100270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A note on out-of-sample prediction, marginal effects computations, and temporal testing with random parameters crash-injury severity models","authors":"Qinzhong Hou ,&nbsp;Xiaoyan Huo ,&nbsp;Junqiang Leng ,&nbsp;Fred Mannering","doi":"10.1016/j.amar.2021.100191","DOIUrl":"https://doi.org/10.1016/j.amar.2021.100191","url":null,"abstract":"<div><p>Random parameters logit models have become an increasingly popular method to investigate crash-injury severities in recent years. However, there remain potential elements of the approach that need clarification including out-of-sample prediction, the calculation of marginal effects, and temporal instability testing. In this study, four models are considered for comparison: a fixed parameters multinomial logit model; a random parameters logit model; a random parameters logit model with heterogeneity in means; and a random parameters logit model with heterogeneity in means and variances. A full simulation of random parameters is undertaken for out-of-sample injury-severity predictions, and the prediction accuracy of the estimated models was assessed. Results indicate, not surprisingly, that the random parameters logit model with heterogeneity in the means and variances outperformed other models in predictive performance. Following this, two alternative methods for computing marginal effects are considered: one using Monte Carlo simulation and the other using individual estimates of random parameters. The empirical results indicate that both methods produced defensible results since the full distributions of random parameters are considered. Finally, two testing alternatives for temporal instability are evaluated: a global test across all time periods being considered, and a pairwise time-period to time-period comparison. It is shown that the pairwise comparison can provide more detailed insights into possible temporal variability.</p></div>","PeriodicalId":47520,"journal":{"name":"Analytic Methods in Accident Research","volume":"33 ","pages":"Article 100191"},"PeriodicalIF":12.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"137210517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}