怠速条件下汽车排气污染物在排气尾流中扩散特性的实验研究

通过实验的方法对怠速条件下汽车排气污染物在排气尾流中的扩散特性进行了研究.测定了怠速条件下汽车排气尾流中的污染物体积分数及其分布,并比较分析了3种不同类型汽车的污染物排放体积分数及其变化.实验结果表明,怠速时汽车排气尾流中的污染物体积分数按照近似指数函数的趋势迅速降低到接近大气背景值;不同类型汽车排气尾流中的污染物体积分数的差别非常明显;排气方向对汽车排放污染物的扩散及其分布具有重要的影响.研究工作可以为怠速工况下汽车排气污染物对周围环境的影响评价提供更多的有用信息.     

公路隧道可吸入颗粒物扩散模型研究

运用大气扩散理论,得到了隧道内自然通风和纵向通风状态下的可吸入颗粒物(PM10)扩散模型,并由隧道口PM10浓度、隧道截面积、隧道内风速,以及车流量和类型等参数,获得了整条隧道内的不同PM10浓度分布.模型表明,随着隧道深度的增加,PM10浓度逐渐增大.通过采用纵向通风的玄武湖隧道各参数,得到了3组不同条件下的PM10扩散模型,并用所得模型计算了隧道内不同深度处PM10的浓度.沿隧道不同深度测得的PM10浓度值的比较结果表明,实际测定值围绕计算值上下波动,两者之间具有良好的一致性.     

浅析城考指标"汽车尾气达标率"

根据城市环境综合整治定量考核指标"汽车尾气达标率"的定义、解释及其实施规定,结合实际,针对性地分析了客观存在的问题,并提出一些可行性建议。     

沈阳市机动车排放污染控制

综述了沈阳市机动车的发展与现状 ,着重探讨了沈阳市机动车尾气给人民生活带来的危害和解决办法 ,讨论了问题的所在 ,并对未来沈阳机动车尾气治理提出建议。     

Decomposition analysis of the effects of vehicle safety technologies on the motor vehicle collision–related mortality rate from 1994 to 2015

Abstract

Objective: Though the mortality rate for motor vehicle collisions (MVCs) has been decreasing since the 1960s with the advent of the first federal seat belt laws in 1968, MVC remains a leading cause of death for individuals aged 1 to 44 years. The purpose of this study is to examine the effects of frontal (FABs) and side airbags (SABs) and electronic stability control (ESC) on the components of the MVC mortality rate.

Methods: The MVC mortality rate from 1994 to 2015 was separated into its components of exposure of vehicles, exposure of travel, collision density, injury incidence, and case fatality rate. Year was categorized on the availability of safety technology in vehicles: 1994–1997 (first-generation FABs mandated), 1998–2001 (sled-certified, second-generation FABs mandated), 2002–2006 (increasing prevalence of SABs and ESC), 2007–2011 (advanced airbags mandated), and 2012–2015 (ESC mandated, SAB in over 90% of vehicles, introduction of advanced safety systems). Relative contributions (RCs) of the components to changes in the MVC-related mortality rate were calculated as the absolute value of the component’s beta coefficient divided by the sum of the absolute values of all components’ beta coefficients. Negative binomial regression–estimated rate ratios (RRs) for the changes in the rate of each component by year category compared to the prior year category.

Results: Significant decreases in the MVC mortality rate were observed for 2007–2011 and 2012–2015. The decrease in 2007–2011 was due in most part to an 18% decrease in the injury incidence (RR?=?0.82, P?<?.0001, RC?=?63%), though there was a noted contribution by the decrease in vehicle miles traveled (RR?=?0.95, P?<?.0001, RC?=?15%). The continued decrease in mortality in 2012–2015 was due is most part to the 10% decreased case fatality rate (RR?=?0.90, P?<?.0001, RC?=?66%) because there was no significant change in the vehicle miles traveled and injury incidence.

Conclusions: The results of this study highlight the effects of vehicle safety technologies on the MVC-related mortality rate and can help direct prevention efforts. Through the study period, there was no meaningful contribution to decreases in the MVC-related mortality rate due to components related to exposure (i.e., vehicles per population and the rate of vehicle miles traveled), suggesting that prevention efforts at decreasing exposure prevalence would have little effect on the MVC-related mortality rate. Instead, prevention efforts should continue to focus on event-phase methods to decrease injury occurrence and mitigate injury severity during the collision.     

机动车尾气VOCs排放特征及减排措施研究

分析了机动车尾气挥发性有机物(VOCs)的排放特征,发现尾气VOCs排放具有明显的日变化和季节变化特征。不同区域不同车型机动车尾气VOCs成分谱略有差异,轻型汽油车尾气VOCs中芳香烃和烷烃含量较高,柴油车烷烃含量较高。尾气排放受机动车保有量、行驶里程、维护保养水平、行驶速度和燃油标准、排放标准等因素影响。从优先控制汽油车、加快机动车更新、采取本地化减排措施、加强多元管理措施、提高科研水平等方面提出了针对性的减排措施。     

重污染天气应对工作中机动车污染减排措施研究

伴随着国民经济的高速发展,越来越多的人拥有了私家车,随之而来的天气污染问题也越来越严重。基于此,本文针对重污染天气应对工作中机动车污染减排措施进行研究。通过加强机动车尾气排放管理、发展太阳能汽车和推动公交出行这三个措施,带动广大市民参与到机动车污染减排的工作中。     

Taking account of the role of safety on vehicle choice using a new generation of discrete choice models

In attitudinal studies safety often appears as an important attribute desired by consumers when buying a new car (Ben-Akiva and Lerman, 1985). However, economic models of vehicle choice usually neglect the role of safety. On the one hand, to capture the qualitative nature of safety and variables related to safety one should consider safety as an underlying construct in a context of latent variable models. The problem is that psychometric models that make use of latent variables do not necessarily provide a complete understanding of agent behavior and may lead to poor predictive power. On the other hand, discrete choice models - although a powerful tool to explain decision making based on utility maximization behavior - fail to include qualitative factors as explanatory variables of the decision process.In this paper, we explore how to model safety through a new generation of discrete choice models which simultaneously consider both a standard discrete choice model and latent causal variables. Using stated preference data concerning purchase intentions of low-emission vehicles in Canada, we test a hybrid choice model to explain consumers’ preferences for safety. Based on the results as well as on the hybrid choice modeling approach, we outline a general framework for the correct modeling of the adoption of safer vehicles and appreciation of safety equipment.     

A study on chest injury mechanism and the effectiveness of a headform impact test for pedestrian chest protection from vehicle collisions

This study was aimed at investigating the injury mechanism of pedestrian chests in collisions with passenger vehicles of various frontal shapes and examining the influence of the local structural stiffness on the chest injury risk by using the headform impact test at the chest contact area of the vehicle. Three simulations of vehicle to pedestrian collisions were conducted using three validated pedestrian finite element (FE) models of three pedestrian heights of 177 (AM50th), 165 and 150 cm and three FE vehicles models representing a one-box vehicle, a minicar and a medium car. The validity of the vehicle models was evaluated by comparing the headform acceleration against the measured responses from headform impact tests. The chest impact kinematics and the injury mechanisms were analyzed in terms of the distribution of the von Mises stress of the ribcage and in terms of the chest deflections. The chest contact locations on the front panel and the bonnet top were identified in connection to the causation of rib fractures. The risk of rib fractures was predicted by using the von Mises stress distribution. The headform impact tests were carried out at the chest contact area on the front panel and bonnet to examine the safety performance with respect to pedestrian chest protection. In simulations of the one-box vehicle to pedestrian collisions, the chest was struck directly by the frontal structure at a high velocity and deformed substantially, since a shear force was generated by the stiff windshield frame. The acceleration of the headform was related to the rib deflections. The injury threshold of the ribcage deflection (42 mm) corresponded to the headform average acceleration of 68 G. In the minicar collision, the chest was struck with the bonnet top and cowl area at a low velocity, and the deformation was small due to the distributed contact force between the chest and the bonnet top. Besides, the ribcage deformation was too small for bridging a relation between the headform accelerations and rib deflections. In the medium car collision, the deformation mode of the chest was similar to that in the minicar collision. The chest collided with the bonnet top at a low velocity and deformed uniformly. The deflection of the ribs had an observable correlation with the headform accelerations measured in the headform impact tests. The frontal shape of a vehicle has a large influence on a pedestrian’s chest loadings, and the chest deformation depends on the size of the pedestrian and the stiffness of the vehicle. The one-box passenger vehicle causes a high chest injury risk. The headform impactor test can be utilized for the evaluation of the local stiffness of a vehicle’s frontal structure. The reduction of the headform acceleration is an effective measure for pedestrian chest protection for specific shapes of vehicles by efficacy in modifying the local structural stiffness.     

Teaching older drivers to navigate GPS technology

Background and objectives: New technologies are being implemented in motor vehicles. One key technology is the electronic navigation system (ENS) that assists the driver in wayfinding, or actually guides the vehicle in higher level automation vehicles. It is unclear how older adults interact with ENSs and the best approach to train older adults to use the devices. The objectives of this study were to explore how older drivers interacted with an ENS while driving on live roadways and how various training approaches impacted older drivers’ ability to accurately enter destinations into the ENS. Research design and methods: In Experiment 1, 80 older drivers navigated unfamiliar routes using an ENS or paper directions and completed a series of ENS destination entry tasks. In Experiment 2, 60 older drivers completed one of three training conditions (ENS video only, ENS video with hands-on training, placebo) to examine the impacts of training on destination entry performance. Results and discussion: Driving performance was aided by the use of the ENS, but many older drivers had difficulty entering destinations into the device (Experiment 1). The combined video with hands-on ENS training resulted in the best overall destination entry performance (Experiment 2). Practical applications: The results suggest older drivers may experience problems entering destinations into ENSs, but training can improve performance. These performance issues may be especially important as more vehicle features require interaction with computer systems to select destinations or other automation related features. Further research is needed to determine how to prepare the next generation of older drivers who will interact with technologies aimed at increasing mobility.