Optimal use of warning signs in traffic

The aim of the paper is to develop a model of drivers’ behaviour particularly designed to analyse the safety and total driving cost implications of warning sign installations. One special feature of the model is that it makes a clear distinction between drivers’ perceived risk values at certain speeds and their respective objective values. When focusing on a certain stretch of road only, the paper concludes that warning signs will increase safety and probably reduce total objective driving costs; that is the sum of time costs and objective expected accident costs. Since drivers’ speed will reduce implying higher time costs per distance, the reduction in total objective driving costs will be lower than the reductions in accident costs. The analysis is then extended to comprise the whole road system and using warning signs prior to curves as an example. Besides the driving conditions in different curves, the analysis shows that the optimal number of signs is dependent on the road authorities’ objectives for road traffic and on how drivers form their risk perceptions. Generally speaking, simulations indicate that the safety and economic benefits of warning sign installation are not very high. When considering the whole road system, warning signs seem, however, to have a greater positive impact on total driving costs than on accident costs.     

Differential effects of traffic sign stimuli upon speeding in school zones following a traffic light interruption

Motorists whose journey has been interrupted by signalized traffic intersections in school zones resume their journey at a faster vehicle speed than motorists who have not been required to stop. Introducing a flashing “check speed” sign 70 m after the traffic intersections counteracts this interruptive effect. The present study examined which aspects of a reminder sign are responsible for reducing the speeding behavior of interrupted motorists. When a sign that combines both written text and flashing lights was introduced, interrupted motorists did not speed, traveling on average 0.82 km/h below the 40 km/h speed limit when measured 100 m from traffic intersections. Alternatively, when only the flashing lights were visible the interrupted motorists sped 3.36 km/h over the 40 km/h speed limit. Similar vehicular speeds were observed when only the written text was visible and when no sign was present (7.67 and 7.49 km/h over the 40 km/h speed limit, respectively). This indicates that static reminder signs add little value over the absence of a school zone reminder sign; the presence of both cues is necessary to fully offset the interruptive effect. This study also highlights the benefit of using exogenous visual cues in traffic signs to capture drivers’ attention. These findings have practical implications for the design and use of traffic signs to increase compliance with posted speed limits.     

Role of drivers' personal characteristics in understanding traffic sign symbols

This study investigated the role of age, marital status, gender, nationality, educational background and monthly income in drivers' comprehension of traffic signs. The populations sampled here were from five Arabian Gulf Countries. A total of 28 symbolic warning and regulatory signs were investigated. A questionnaire specially prepared to collect the necessary data was distributed to over 9000 drivers in the five countries; 4774 responded (53%). The results indicated substantial problems with the level of comprehension among the drivers about the traffic signs. The percentages of drivers who correctly identified the regulatory signs and warning signs were around 55 and 56%, respectively. Age, gender, education and income played major roles in determining drivers' comprehension of signs, whereas marital status showed no significant effect. Drivers who are young, female, those with lower levels of education or lower incomes understand the signs significantly worse than drivers who are older, male, with higher levels of education or higher incomes. Drivers from Europe and USA are significantly better than Asian and Arab drivers. These findings are believed to be important for the designers of road signs for international applications.     

基于可视化呈现的数字化健康信息认知研究

目的 研究数字化健康信息的呈现状态和呈现方式对年轻用户健康信息认知理解的影响。方法 采用两因子组内设计的人因学实验,测试了18名年轻受试者在两种信息呈现状态（静态呈现,动态呈现）及三种信息呈现方式（条形图,仪表图,文本型）下的认知绩效、主观感知及眼动行为,并采用重复测量方差分析法分析实验数据。结果 信息呈现状态显著影响用户认知理解绩效,动态呈现方式能有效降低用户信息搜索时间。呈现方式显著影响感知易用性和满意度等主观评价指标,两种图形类方式主观感知评价显著高于文本型。信息呈现状态和呈现方式对眼动行为存在显著主效应及交互作用,条形图和文本型在动、静态呈现时的首次注视时间无显著差异,但动态仪表图的首次注视时间晚于静态仪表图。图形类呈现方式的总注视时长较之于文本型也较短,其信息认知效率较高。结论 呈现状态中,动态呈现能够提高用户提取重要信息的效率;而呈现方式中,图形类呈现方式有更好的用户主观认知评价。研究结果有助于揭示呈现状态和呈现方式对数字化健康信息认知的影响机制,为优化数字化健康信息的编码设计提供了指导。     

气象灾害预警信息广播系统总体设计与信息编码研究

提出新一代气象灾害预警信息广播系统的总体设计框架,并对气象灾害预警信息编码进行深入研究,制定气象预警信息编码格式.气象预警信息广播系统能够迅速接收、处理各种气象灾害信息,在最短的时间内向特定的区域、部门、人群发布预警信息;预警信息可以覆盖到全国,有效解决气象预警信息发布的"最后1公里"问题.     

Warning symbols as reminders of hazards: impact of training

Prior research indicates that many warning symbols are poorly understood. However Lesch [Lesch, M.F., 2003. Comprehension and memory for warning symbols: Age-related differences and impact of training. J. Safety Res. 34, 495–505] found that accident scenarios could be used to improve comprehension of warning symbols. The current study further investigated the potential benefits of accident scenario training. During training, warning symbols with verbal labels corresponding to the meaning of the symbol were paired with accident scenarios which expanded on the nature of the hazard, the required/prohibited actions, as well as the possible consequences of failing to comply. A number of measures were obtained prior to, and following (immediately and 2 weeks later), the accident scenario training: comprehension across three knowledge types (verbal label, required/prohibited actions, potential consequences of failure to comply), ratings of agreement with statements reflecting perceived control, and ratings of hazard and intent to comply. Benefits of training were observed on all dependent measures: Comprehension improved from 43 to 82% correct, reaction times were reduced by about 2 s, and level of confidence in correct responses increased by 23%. Ratings of perceived hazard, intent to comply, and perceived control over accident/injury involvement also increased. It is suggested that accident scenario training can be used to help prevent accidents and injuries by ensuring that responses to warnings are “sure and swift”.     

How does a collision warning system shape driver's brake response time? The influence of expectancy and automation complacency on real-life emergency braking

Brake Reaction Time (BRT) is an important parameter for road safety. Previous research has shown that drivers' expectations can impact RT when facing hazardous situations, but driving with advanced driver assistance systems, can change the way BRT are considered. The interaction with a collision warning system can help faster more efficient responses, but at the same time can require a monitoring task and evaluation process that may lead to automation complacency. The aims of the present study are to test in a real-life setting whether automation compliancy can be generated by a collision warning system and what component of expectancy can impact the different tasks involved in an assisted BRT process. More specifically four component of expectancy were investigated: presence/absence of anticipatory information, previous direct experience, reliability of the device, and predictability of the hazard determined by repeated use of the warning system. Results supply indication on perception time and mental elaboration of the collision warning system alerts. In particular reliable warning quickened the decision making process, misleading warnings generated automation complacency slowing visual search for hazard detection, lack of directed experienced slowed the overall response while unexpected failure of the device lead to inattentional blindness and potential pseudo-accidents with surprise obstacle intrusion.     

Using reflective clothing to enhance the conspicuity of bicyclists at night

Bicycling at night is more dangerous than in the daytime and poor conspicuity is likely to be a contributing factor. The use of reflective markings on a pedestrian's major joints to facilitate the perception of biological motion has been shown to greatly enhance pedestrian conspicuity at night, but few corresponding data exist for bicyclists. Twelve younger and twelve older participants drove around a closed-road circuit at night and indicated when they first recognized a bicyclist who wore black clothing either alone, or together with a reflective bicycling vest, or a vest plus ankle and knee reflectors. The bicyclist pedalled in place on a bicycle that had either a static or flashing light, or no light on the handlebars. Bicyclist clothing significantly affected conspicuity; drivers responded to bicyclists wearing the vest plus ankle and knee reflectors at significantly longer distances than when the bicyclist wore the vest alone or black clothing without a vest. Older drivers responded to bicyclists less often and at shorter distances than younger drivers. The presence of a bicycle light, whether static or flashing, did not enhance the conspicuity of the bicyclist; this may result in bicyclists who use a bicycle light being overconfident of their own conspicuity at night. The implications of our findings are that ankle and knee markings are a simple and very effective approach for enhancing bicyclist conspicuity at night.     

Segmentation of lines based on point densities--an optimisation of wildlife warning sign placement in southern Finland

Current and previous placement of wildlife warning signs by the Finnish Road Administration is based on suggestions from hunting associations and individuals. The problem within this practice is that the placement of warning signs is not a transparent process. Within this paper, we evaluate the current placement of wildlife warning signs for the Uusimaa region in southern Finland and develop a method to optimise warning sign placement using kernel density estimations, which are based on existing wildlife-vehicle accident records. The contour lines of these densities can indicate the road sections to be marked with warning signs. To apply a well-documented computational method, based on these moose and white-tailed deer accident locations, assists the Finnish Road Administration in their task to place, replace and assess wildlife-warning signs for specific road sections.     

Effects of color scheme and message lines of variable message signs on driver performance

The advancement in variable message signs (VMS) technology has made it possible to display message with various formats. This study presented an ergonomic study on the message design of Chinese variable message signs on urban roads in Taiwan. Effects of color scheme (one, two and three) and number of message lines (single, double and triple) of VMS on participants’ response performance were investigated through a laboratory experiment. Results of analysis showed that color scheme and number of message lines are significant factors for participants’ response time to VMS. Participants responded faster for two-color than for one- and three-color scheme. Participants also took less response time for double line message than for single and triple line message. Both color scheme and number of message lines had no significant effect on participants’ response accuracy. The preference survey after the experiment showed that most participants preferred two-color scheme and double line message to the other combinations. The results can assist in adopting appropriate color scheme and number of message lines of Chinese VMS.     

The role of attention in horizontal curves: a comparison of advance warning, delineation, and road marking treatments

Horizontal curves have been recognized as a significant safety issue for many years, a more important factor than road width or sight distance. The research literature suggests that driver errors associated with horizontal curves result from three inter-related problems: failures of driver attention, misperceptions of speed and curvature, and poor lane positioning. To examine the roles of attentional, perceptual, and lane placement factors in driver behaviour at curves, two groups of curve treatments were identified for testing with a driving simulator. The first group of treatments consisted of four combinations of warning signs designed to alert drivers to the presence of curves and produce a reduction in curve approach speeds. The second group was comprised of several types of road markings designed to affect drivers' speed and lane position as they drove through curves. The results indicated that advance warning signs by themselves were not as effective at reducing speeds as when they were used in conjunction with chevron sight boards and/or repeater arrows. Of the road marking treatments only rumble strips produced any appreciable reductions in speed. A herringbones road marking was found to produce significant improvements in drivers' lane positions, effectively flattening the drivers' paths through the curves. A treatment combining the herringbones treatment with chevron and repeater arrow signs produced both a reliable reduction in speed as well as improved lane positions. The results are interpreted as evidence that treatments that highlight perceptual cues are the most effective means of moderating drivers' curve speeds.     

基于中小学生出行及认知特点的交通标志改进的探讨

目的从交通安全的角度出发,基于中小学生的出行特点和认知特点,提出现行交通标志设计改进方案。方法设计实验,抽样调查中小学生2400名,分析现有交通标志存在的缺陷。结果现有交通标志中,中小学生认知理解正确率为67.92%,注视时长885ms,红色标志认读正确率87.3%;现有交通标志存在部分不易理解、设计单调、静态交通标志高度欠合理、人性化不足等问题,针对交通标志的颜色、图案、材料、位置、高度等方面缺陷提出可行性改进方案,进一步提高交通标志的趣味性和可用性。结论结合中小学生的出行和认知特点来改进现有交通标志,可以改善现有交通标志成人化、有歧义、不具亲和力等缺陷,有利于中小学生的出行安全更进一步得到保障。     

Reductions in driver speed using posted feedback of speeding information: social comparison or implied surveillance?

Reducing driver speed has an essential role to play in traffic safety. This study measured the effect of a roadside sign, in a 50 km/h zone, that consecutively displayed one of three messages:

1. The average speed at the site: this message was designed to induce “social comparison” whereby drivers may reduce their speed in order to comply with the behaviour of the majority.

2. A warning that drivers’ speeds were being measured: this was intended to imply surveillance whereby drivers may reduce speed in order to avoid possible enforcement action.

3. A combination of both messages, to see if both together would have a greater effect than either alone.

The speed of drivers travelling along a busy urban road (11,500 cars daily in each direction) was measured using inductive loop detectors. The proportion of drivers travelling 60 km/h or less increased with all three messages, suggesting that both social comparison and implied surveillance are mechanisms by which driver speed may be reduced. However, the speed reductions were not as great as in previous studies of feedback signs. This may be due to differences in the existing safety culture.     

Measuring driver responses at railway level crossings

Railway level crossings are amongst the most complex of road safety control systems, due to the conflicts between road vehicles and rail infrastructure, trains and train operations. Driver behaviour at railway crossings is the major collision factor. The main objective of the present paper was to evaluate the existing conventional warning devices in relation to driver behaviour. The common conventional warning devices in Australia are a stop sign (passive), flashing lights and a half boom-barrier with flashing lights (active). The data were collected using two approaches, namely: field video recordings at selected sites and a driving simulator in a laboratory. This paper describes and compares the driver response results from both the field survey and the driving simulator. The conclusion drawn is that different types of warning systems resulted in varying driver responses at crossings. The results showed that on average driver responses to passive crossings were poor when compared to active ones. The field results were consistent with the simulator results for the existing conventional warning devices and hence they may be used to calibrate the simulator for further evaluation of alternative warning systems.     

Microsimulation modelling of driver behaviour towards alternative warning devices at railway level crossings

Level crossings are amongst the most complex of road safety issues, due to the addition of rail infrastructure, trains and train operations. The differences in the operational characteristics of different warning devices together with varying crossing, traffic or/and train characteristics, cause different driver behaviour at crossings. This paper compares driver behaviour towards two novel warning devices (rumble strips and in-vehicle audio warning) with two conventional warning devices (flashing light and stop sign) at railway level crossings using microsimulation modelling. Two safety performance indicators directly related to collision risks, violation and time-to-collision, were adopted. Results indicated the active systems were more effective at reducing likely collisions compared to passive devices. With the combined application of driving simulation and traffic microsimulation modelling, traffic safety performance indicators for a level crossing can be estimated. From these, relative safety comparisons for the different traffic devices are derived, or even for absolute safety evaluation with proper calibration from field investigations.     

增强现实平视显示行人预警系统的视觉编码设计研究

目的 随着影像和雷达传感器技术的发展,车载预警系统可以更快、更广和更高精度地实现对于行人的识别与追踪。相较于其他预警方式,增强现实平视显示预警(Augmented Reality Head-up Display,AR-HUD)可以为用户提供实时、准确的预警信息并降低用户因视线切换而带来的驾驶风险,具有较大的应用潜力。已有研究表明,预警信息的编码方式对预警效果影响显著,然而目前AR-HUD预警方式的设计标准尚未制定,因此,探究AR-HUD的预警编码方式对其应用具有重要意义。方法 以AR-HUD行人预警为例,基于颜色、边框形状、闪烁等设计元素对预警信息进行编码设计,从眼动指标、行为指标和主观指标对各编码方式进行多模态的量化分析和评估,提出相应的设计建议。结论 采用颜色编码可以显著提升编码可识别性,保持低漏报率的同时有较短的反应时,而非颜色编码利用冗余编码可以增强编码可识别性;采用形状编码会降低编码可理解性,但会减小用户对预警的漏报率;闪烁编码会增大对预警的漏报率和反应时;用户主观上认为冗余编码比单维编码有更强的警示性。研究结论可为AR-HUD的交互设计和实车应用提供相关理论支撑。     

The effect of ice warning signs on ice-accident frequencies and severities

Signing of non-permanent road surface conditions, such as ice, is difficult because hazard formation, location, and duration are unpredictable. Subsequently, many state transportation departments have begun to question the sensibility of expending material and personnel resources to maintain ice warning signs when little proof exists of their effectiveness in improving highway safety. This research statistically studies the effectiveness of ice warning signs in reducing accident frequency and accident severity in Washington State. Our findings show that the presence of ice warning signs was not a significant factor in reducing ice-accident frequency or ice-accident severity. However, we were able to identify significant spatial, temporal, traffic, roadway and accident characteristics that influenced ice-accident frequency and severity. The identification of these characteristics will allow for better placement of ice warning signs and improvements in roadway and roadside design that can reduce the frequency and severity of ice-related accidents.     

Gradient Elasticity Theories in Statics and Dynamics - A Unification of Approaches

Partly in response to a communication recently published in this journal on apparent inconsistencies between certain continuum and atomistic formulations of gradient elasticity (Yang and Guo 2005), we further elaborate on this issue in view of results and works not known or not cited in the aforementioned communication. In particular, we unify the concepts and motivations of two different formats of gradient elasticity. The first format was motivated for use in statics and aims at removing strain singularities. The second format was motivated for use in dynamics and aims at describing wave dispersion. We suggest here an alternative format of gradient elasticity that is dispersive, while its static version is identical to the first format mentioned above. Also, procedures are outlined by which the higher-order coefficients can be related to micro-structural properties. Finally, solution methods are described for static and dynamic analysis.     

Adapting ISA system warnings to enhance user acceptance

Inappropriate speed is a major cause of traffic accidents. Different measures have been considered to control traffic speed, and intelligent speed adaptation (ISA) systems are one of the alternatives. These systems know the speed limits and try to improve compliance with them. This paper deals with an informative ISA system that provides the driver with an advance warning before reaching a road section with singular characteristics that require a lower safe speed than the current speed. In spite of the extensive tests performed using ISA systems, few works show how warnings can be adapted to the driver. This paper describes a method to adapt warning parameters (safe speed on curves, zone of influence of a singular stretch, deceleration process and reaction time) to normal driving behavior. The method is based on a set of tests with and without the ISA system. This adjustment, as well as the analysis of driver acceptance before and after the adaptation and changes in driver behavior (changes in speed and path) resulting from the tested ISA regarding a driver's normal driving style, is shown in this paper. The main conclusion is that acceptance by drivers increased significantly after redefining the warning parameters, but the effect of speed homogenization was not reduced.     

Bicyclists overestimate their own night-time conspicuity and underestimate the benefits of retroreflective markers on the moveable joints

Conspicuity limitations make bicycling at night dangerous. This experiment quantified bicyclists’ estimates of the distance at which approaching drivers would first recognize them. Twenty five participants (including 13 bicyclists who rode at least once per week, and 12 who rode once per month or less) cycled in place on a closed-road circuit at night-time and indicated when they were confident that an approaching driver would first recognize that a bicyclist was present. Participants wore black clothing alone or together with a fluorescent bicycling vest, a fluorescent bicycling vest with additional retroreflective tape, or the fluorescent retroreflective vest plus ankle and knee reflectors in a modified ‘biomotion’ configuration. The bicycle had a light mounted on the handlebars which was either static, flashing or off. Participants judged that black clothing made them least visible, retroreflective strips on the legs in addition to a retroreflective vest made them most visible and that adding retroreflective materials to a fluorescent vest provides no conspicuity benefits. Flashing bicycle lights were associated with higher conspicuity than static lights. Additionally, occasional bicyclists judged themselves to be more visible than did frequent bicyclists. Overall, bicyclists overestimated their conspicuity compared to previously collected recognition distances and underestimated the conspicuity benefits of retroreflective markings on their ankles and knees. Participants mistakenly judged that a fluorescent vest that did not include retroreflective material would enhance their night-time conspicuity. These findings suggest that bicyclists have dangerous misconceptions concerning the magnitude of the night-time conspicuity problem and the potential value of conspicuity treatments.