Travel time reliability(TTR) modeling has gain attention among researchers’ due to its ability to represent road user satisfaction as well as providing a predictability of a trip travel time.Despite this significant ...Travel time reliability(TTR) modeling has gain attention among researchers’ due to its ability to represent road user satisfaction as well as providing a predictability of a trip travel time.Despite this significant effort,its impact on the severity of a crash is not well explored.This study analyzes the effect of TTR and other variables on the probability of the crash severity occurring on arterial roads.To address the unobserved heterogeneity problem,two random-effect regressions were applied;the Dirichlet random-effect(DRE)and the traditional random-effect(TRE) logistic regression.The difference between the two models is that the random-effect in the DRE is non-parametrically specified while in the TRE model is parametrically specified.The Markov Chain Monte Carlo simulations were adopted to infer the parameters’ posterior distributions of the two developed models.Using four-year police-reported crash data and travel speeds from Northeast Florida,the analysis of goodness-of-fit found the DRE model to best fit the data.Hence,it was used in studying the influence of TTR and other variables on crash severity.The DRE model findings suggest that TTR is statistically significant,at 95 percent credible intervals,influencing the severity level of a crash.A unit increases in TTR reduces the likelihood of a severe crash occurrence by 25 percent.Moreover,among the significant variables,alcohol/drug impairment was found to have the highest impact in influencing the occurrence of severe crashes.Other significant factors included traffic volume,weekends,speed,work-zone,land use,visibility,seatbelt usage,segment length,undivided/divided highway,and age.展开更多
根据气体介质温度场声学测量原理可知,只有实现声波飞渡时间的高精度、快速测量,才能保证温度场反演测量的高精度和测量的实时性。为此,将伪随机序列编码技术与互相关分析方法相结合,设计了一种声波飞渡时间高精度、快速测量系统,并对...根据气体介质温度场声学测量原理可知,只有实现声波飞渡时间的高精度、快速测量,才能保证温度场反演测量的高精度和测量的实时性。为此,将伪随机序列编码技术与互相关分析方法相结合,设计了一种声波飞渡时间高精度、快速测量系统,并对其进行了仿真研究。仿真结果表明:该方案是可行的和有效的。即当不加入伪随机序列时,声发射与接收信号间虽有相关性,但会出现连续重复峰值,无法求得声波飞渡时间;同时,并非采样精度越高越好。当载波频率为40 k Hz时,采样频率选取200 k Hz时的测量精度最高且速度最快,且测量精度绝对误差小于10,能够满足声学测温的高精度和实时测量的要求。展开更多
基金the Center for Accessibility and Safety for an Aging Population at Florida State UniversityFlorida A&M UniversityUniversity of North Florida for funding support in research
文摘Travel time reliability(TTR) modeling has gain attention among researchers’ due to its ability to represent road user satisfaction as well as providing a predictability of a trip travel time.Despite this significant effort,its impact on the severity of a crash is not well explored.This study analyzes the effect of TTR and other variables on the probability of the crash severity occurring on arterial roads.To address the unobserved heterogeneity problem,two random-effect regressions were applied;the Dirichlet random-effect(DRE)and the traditional random-effect(TRE) logistic regression.The difference between the two models is that the random-effect in the DRE is non-parametrically specified while in the TRE model is parametrically specified.The Markov Chain Monte Carlo simulations were adopted to infer the parameters’ posterior distributions of the two developed models.Using four-year police-reported crash data and travel speeds from Northeast Florida,the analysis of goodness-of-fit found the DRE model to best fit the data.Hence,it was used in studying the influence of TTR and other variables on crash severity.The DRE model findings suggest that TTR is statistically significant,at 95 percent credible intervals,influencing the severity level of a crash.A unit increases in TTR reduces the likelihood of a severe crash occurrence by 25 percent.Moreover,among the significant variables,alcohol/drug impairment was found to have the highest impact in influencing the occurrence of severe crashes.Other significant factors included traffic volume,weekends,speed,work-zone,land use,visibility,seatbelt usage,segment length,undivided/divided highway,and age.
文摘根据气体介质温度场声学测量原理可知,只有实现声波飞渡时间的高精度、快速测量,才能保证温度场反演测量的高精度和测量的实时性。为此,将伪随机序列编码技术与互相关分析方法相结合,设计了一种声波飞渡时间高精度、快速测量系统,并对其进行了仿真研究。仿真结果表明:该方案是可行的和有效的。即当不加入伪随机序列时,声发射与接收信号间虽有相关性,但会出现连续重复峰值,无法求得声波飞渡时间;同时,并非采样精度越高越好。当载波频率为40 k Hz时,采样频率选取200 k Hz时的测量精度最高且速度最快,且测量精度绝对误差小于10,能够满足声学测温的高精度和实时测量的要求。
