Opposite Lane Research Articles

Effects of Oncoming Vehicle Size on Overtaking Judgments

In 2011, 89,000 accidents in the United States involved a vehicle passing another vehicle, which resulted in 740 deaths and 19,000 injuries (NHTSA, 2011). When passing a vehicle on a two-way highway (overtaking), a driver often must temporarily cross into the opposite lane of traffic, and may face oncoming vehicles. To avoid a collision with an oncoming vehicle, the overtaking driver must estimate the time remaining until a collision would occur with the vehicle. Although information about an oncoming vehicle’s time-to-collision is theoretically available in the optical invariant tau (Lee, 1976), it is below threshold during high-speed overtaking maneuvers, which require a large passing distance. Under such conditions, we expect drivers to rely on the oncoming vehicle’s apparent distance and velocity, and thus depth cues such as relative size. We used a driving simulator to determine whether overtaking judgments are influenced by an oncoming vehicle’s size, and on whether such judgments differ between active driving and passive viewing. Twenty-four participants viewed computer-generated scenes in which they were following a lead vehicle on a straight, two-lane, two-way highway. At the start of each scene an oncoming vehicle (motorcycle, car, delivery truck) was visible in the opposite lane. Seven seconds after the scene an auditory tone signaled participants to make an overtaking decision. Participants in the active condition passed the lead vehicle if they thought it was safe to do so. Participants in the passive condition indicated whether it was safe to pass by pressing buttons on the steering wheel. We manipulated the participant’s (and lead vehicle’s) speed (48.28 km/h, 64.37 km/h, 80.47 km/h) and the oncoming vehicle’s speed (72.42 km/h, 88.51 km/h, 104.61 km/h) and distance when the tone occurred (457.20 m, 609.60 m). This resulted in 9 safe and 9 unsafe temporal gaps based on an equation generated from analyses of actual overtaking performance (Gordon & Mast, 1970). Results indicated more accepted gaps and more false alarms (accepted gap when unsafe) in front of motorcycles than larger cars or trucks. The judgments made by participants in the active and passive conditions did not differ. Analyses of signal detection theory measures of sensitivity (d-prime) and response bias (beta) suggested that the effect of vehicle size was due to shifts in response bias rather than sensitivity. Results have implications for traffic safety and for the potential role of driver-assistance technologies.

End-to-End Performance for SCF-Based Vehicular Routing Over Multiple Communication Gaps

In Vehicular Ad Hoc Networks (VANETs), there are generally very few communicating vehicles along a routing path in areas with low traffic density. Existing schemes based on the Store-Carry-Forward (SCF) technique utilize a moving vehicle to bridge the communication gap between two disconnected vehicles on the opposite lane. This letter investigates network performance over multiple communication gaps in SCF-based vehicular routing. To investigate the influence of the transmission range on the end-to-end delivery delay, we develop an analytical model to quantify the performance in terms of the Laplace transform of the end-to-end delay via SCF-based vehicular routing. Extensive simulation results are presented to validate the proposed model.

Capacity and Safety of Passing Zones on Two-Lane Rural Highways: A Review of Theory and Practice

The majority of the road infrastructure in developing countries consists oftwo-lane highways with one lane in each travel direction. Operational efficiency of these highways is derived fromintermittent passing zones where fast vehicles are permitted by design to pass slow vehicles using the opposite traffic lane. Passing zonescontributeto reduction oftravel delay and queuing of fast vehiclesbehind slow vehicles. Thishoweverincreases crash risks between passing and opposite vehiclesespecially at high traffic volumesdue to reduction of passing opportunities.Reduction of passing-related crash risks is therefore a primary concern ofpolicy makers, planners, and highway design engineers. Despite the wide application of passing zones on two-lane highways, there is limited knowledge on the underlying causal mechanisms that exacerbate crash risks, and the essential tools to assess safety of the passing zones.This thesis presentsa methodology to appraisesafety of two-lane rural highways based on observed operation of passing zones.Theproposed methodology takes into accountthe impact of traffic and geometric factors onthe rate passing maneuvers end insidepassing zonesand in the no-passing zones, adequacy ofthe designpassing sight distance,and time-to-collision at the end of passing maneuvers.Thethesis is comprised offive papers addressing capacity and safety aspectsof passing zoneson two-lane rural highways. Paper Ipresents a review of the literature on capacity and safety of passing zones. Paper IIdiscusses adequacy of the design passing sight distance based on the sight distance required to complete a passing maneuverusing observed data. Paper IIIdiscusses formulation, estimation, and application of a model to predict the passing rate using geometric and traffic factors, and applications. Paper IVdiscusses risk appraisal of the passing process based on the probability to complete passing maneuvers with time-to-collision less than 3.0 seconds taking into account the accepted gap in the opposite direction and the passing duration. Paper Vdiscusses formulation and estimation of models to predict the probability and the rate at which passing maneuvers end in a no-passing zone, and applications.Resultsshow that passing zones of lengths between 1.30and 2.50km aregood for both operational efficiency and safety.Passing zones of lengths between 0.50and 1.30km exhibitincreasing crash risks resulting from delayed passing maneuvers thatend in the no-passing zone where the sight distance is limited to evadepotential collisions. Safety of these passing zones could be enhanced with additional signage to indicate the farthestpoint along a passing zone that maneuvers can be initiated so as not to end in a no-passing zone. Passing zones less than 0.50km compel drivers to commence passing maneuvers close to the beginning of the passing zone,and should be avoided during design for safety reasons.The results further show that the passing rate depends on the length of the passing zone, absolute vertical grade, traffic volume in two travel directions, directional split, 85thpercentile speed of free flow vehicles,and percent of heavy vehicles in the subject direction. The peak-passing rate also known as the passing capacity occurs at 200, 220, and 240vph in the subject direction for 50/50, 55/45, and 60/40directional splits, respectively. The rate at which passing maneuvers end in a no-passing zone increaseswith traffic volume and unequal distribution of traffic in two directions, absolute vertical grade, and percent of heavy vehiclesin the subject direction. The thesis furtherdiscusses practical applications of the study findings in highway planning and design to enhancesafety and improve operational efficiency of two-lane rural highways.

Behaviour of American Crows (<em>Corvus brachyrhynchos</em>) when encountering an oncoming vehicle

A carrion feeder attempting to forage on a road benefits greatly from an appropriate response to vehicular traffic. In this observational study, we tested the ability of American Crows (Corvus brachyrhynchos) to judge the behaviour of fast-moving vehicles and avoid collision on a narrow road. Unsurprisingly, American Crows feeding in the same lane as the approaching vehicle always flew off, but interestingly, a significant proportion of American Crows in the opposite lane chose to remain on the road. In addition, 21% of the American Crows in the same lane as the approaching vehicle walked over to the opposite lane to avoid injury, but none of the American Crows in the opposite lane walked over to the lane in which the vehicle was approaching. These are among the first quantitative data indicating that a non-human animal can detect the directionality of oncoming vehicles on a road and, like humans, actively move out of the way or switch lanes to avoid death based on an understanding of the bahaviour of vehicular traffic.

A Stable Routing Protocol for Vehicles in Urban Environments

The vehicular ad hoc network (VANET) is an essential technology that enables the deployment of the intelligent transportation system (ITS), which improves the traffic safety and efficiency. For the efficient message delivery in VANETs, it is desirable to provide a reliable and stable VANET routing protocol. However, VANET routing is challenging since the VANET is fundamentally different from conventional wireless ad hoc networks; vehicles move fast, and the network topology changes rapidly, causing intermittent and dynamic link connectivity. In this paper, we propose a VANET routing protocol that works based on the real-time road vehicle density information in order to provide fast and reliable message delivery so that it can adapt to the dynamic vehicular urban environment. In the proposed mechanism, each vehicle computes the real-time traffic density of the road to which it belongs from the beacon messages sent by vehicles on the opposite lane and its road information table. Using the road traffic density information as a routing metric, each vehicle establishes a reliable route for packet delivery. We compare our proposed mechanism with the well-known GPSR via NS-2 based simulations and show that our mechanism outperforms GPSR in terms of both delivery success rate and routing overhead.

Factors Affecting Median Cable Barrier Crash Frequency: New Insights

This study evaluated the impact of roadway cross-sectional and geometric features, traffic characteristics, and median cable barrier placement to the frequency of median-related crashes through statistical modeling using multiyear data. A unique aspect of the model specification was the inclusion of median cable barrier placement data, horizontal curve data, and differential elevation of opposite travel lanes. Negative binomial model was used in linearizing and quantifying these factors with respect to median crossover crash frequency. The variables that were found to significantly influence the frequency of median crashes include the number of lanes, differential elevation, and cable barrier offset from the inside shoulder. Increasing traffic volume was found to increase the frequency of median barrier crashes as well as the presence of curves on a median barrier section was found to increase the frequency of crashes. Higher differential elevation between opposite travel lanes was also found to increase the frequency of median barrier crashes. Increasing the median barrier offset from the inside shoulder of the travel way decreases median barrier injury and fatal crash frequency. Segments with a higher number of lanes and a wider median width were associated with low crash frequencies.

The Use of Automotive Radars in Video-Based Overtaking Assistance Applications

Overtaking on rural roads may cause severe accidents when oncoming traffic is detected by a driver too late, or its speed is underestimated. Recently proposed cooperative overtaking assistance systems are based on real-time video transmission, where a video stream captured with a camera installed at the windshield of a vehicle is compressed, broadcast through the wireless channel, and displayed to the drivers of vehicles driving behind. In such a system, it is of ultimate importance to deliver video information about the opposite lane with low end-to-end latency and good visual quality. In this paper, we propose reallocating the wireless channel resources in favor of the part of the captured video frame containing the image of the oncoming vehicle. To achieve this goal, we apply automotive radar for oncoming vehicle detection, and we use the image of this vehicle as a region-of-interest (ROI) for the video rate control. We present the theoretical framework, which describes the basics of such an approach and can serve as a useful guideline for the future practical implementation of the overtaking assistance systems. The benefits of our proposal are demonstrated in relation to the practical scenario of H.264/Advance Video Coding (AVC), IEEE 802.11p/Wireless Access for Vehicular Environments (WAVE) intervehicle communication standards, and currently used automotive radars.

교차로에서의 안전 좌회전을 위한 차량간 통신 기반 알고리즘 설계 및 구현

차량 통신 프로토콜은 IEEE 802.11 WG과 P1609에서 진행하고 있는 WAVE(Wireless Access in Vehicular Environments)가 대표적이며, 보안 등을 제외한 MAC과 PHY에 대한 부분은 표준으로 제정되었다. 이러한 차량통신을 이용하여 운전자들의 안전과 전체 교통 흐름의 원활한 통제를 위해 국내외에서 많은 프로젝트가 진행되고 있다. 따라서 본 논문에서는 교차로에서 좌회전 시도 시에 위험 상황이 예상되면 운전자에게 알려주기 위한 차량간 통신 기반 안전서비스 알고리즘을 설계하였고, 이를 실제 구현하였다. 제안하는 알고리즘은 자차와 반대편에서의 접근차량에 대한 모델을 구성하고 충돌 위험이 있을 경우 운전자에게 HMI(Human Machine Interface)를 통해 경고를 주게 된다. 본 안전 서비스의 성능 테스트를 위해 테스트 차량을 이용하여 알고리즘을 시스템에 탑재하였으며, 테스트 케이스를 구성하여 성능 시험장에서 검증하였다. 테스트 결과로써, 우수한 성능을 나타냈으며, 앞으로 차량 통신 인프라가 설치된다면 V2I(Vehicle to Infrastructure) 통신을 이용하여 본 알고리즘을 보다 정밀하게 보완해야 할 것이다. WAVE(Wireless Access in Vehicular Environments) is a representative V2V communication protocol and its standards of MAC and PHY parts except for security were published. In order to control traffic flow and ensure driver's safety using V2V communication, various projects are conducting. In particular, safety application has been researched. Therefore, in this paper, we designed the safety application algorithm, which informs a driver of the dangerous status when driver tries to turn left in an intersection and we also implemented the algorithm. Proposed algorithm configures a model for a host vehicle and a vehicle coming in opposite lane and in case that there is collision hazard it provides warning message to driver by using HMI. In order to evaluate the proposed algorithm's performance, we configured the test bed using test vehicles and we tested the algorithm on proving ground with the composed test scenarios. As test results, our system showed excellent performance. If the infrastructures for V2I communications are constructed, we will optimize our system more precisely and stably.

Development of More Realistic Overtaking Behavior Model in CA-Based Two-Lane Highway Environment

2차로 양방향 교통류의 주요한 특징은 저속차량으로 인한 차량군과 차량추월이다. 따라서 교통류 모의실험을 이용하여 2차로 도로 교통류의 미시적 분석하기 위해서는 차량군의 행태와 더불어 대항차로를 이용한 추월 행태를 동시에 구현하는 차량모형의 개발이 필수적이다. 이에 따라 국내에서는 이산적 시공간을 기반으로 2차로 양방향 교통류 모형이 소개 되었다(윤병조, 2011). 그러나 선행연구는 임계밀도 이하의 안정 교통류 상태에서 차량추월 행태의 설명력이 우수한 반면, 불안정 교통류상태에서 차량추월의 행태를 설명하기에는 단점을 가지고 있었다. 따라서 본 연구에서는 선행연구를 기반으로 불안정 교통류 상태에서 보다 현실적으로 차량추월을 구현하는 모형을 수정/개발하였다. 개발된 모형의 평가를 위하여 모의실험을 수행한 결과, 차량추종모형은 교통류의 미시적 특성중 하나인 가다서다(Stop-and-go) 현상을 설명하면서 거시적 교통류 관계를 효과적으로 구현 하였으며, 추월모형은 대향방향 교통류와 차량추월 확률변수의 조건에 따라 불안정 교통류상태에서도 합리적으로 차량추월을 설명하였다. 따라서 본 논문에서 제시된 차량모형은 보다 더 현실적으로 2차로 도로 교통류의 분석에 활용될 수 있을 것으로 판단된다. The two characteristics of two-lane-and-two-way traffic flow are platoon and overtaking triggered by low-speed vehicle. It is crucial to develop a robust model which simultaneously generates the behaviors of platoon by low-speed vehicle and overtaking using opposite lane. Hence, a microscopic two-lane and two-way vehicle model was introduced (B. Yoon, 2011), which is based on CA (Cellular Automata) which is one of discrete time-space models, in Korea. While the model very reasonably explains the behaviour of overtaking low-speed vehicle in stable traffic flow below critical density, it has shortcomings to the overtaking process in unstable traffic flow above the critical density. Therefore, the objective of this study is to develope a vehicle model to more realistically explain overtaking process in unstable traffic flow state based on the model developed in the previous study. The experimental results revealed that the car-following model robustly generates the various macroscopic relationships of traffic flow generating stop-and-go traffic flow and the overtaking model reasonably explains the behaviors of overtaking under the conditions of both opposite traffic flow and stochastic parameter to consider overtaking in unstable traffic flow state. The vehicle model presented in this study can be expected to be utilized for the analysis of two-lane-and-two-way traffic flows more realistically than before.

A hierarchical fuzzy system for modeling driver’s behavior

The study of human behavior during driving is of primary importance for improving the driver’s security. In this study, we propose a hierarchical driver_vehicle_environment fuzzy system to analyze driver’s behavior under stress conditions on a road. We include climate, road and car conditions in fuzzy modeling. For obtaining fuzzy rules, experts’ opinions are benefited by means of questionnaires on effects of parameters such as climate, road and car conditions on driving capabilities. The number of fuzzy rules is optimized by Particle Swarm Optimization (PSO) algorithm. Also the frequency of pressing on brake and gas pedals and the number of car’s direction changes are used to determine the driver’s behavior under different conditions. Three different positions are considered for driving and decision making; one position in driving lane and two positions in opposite lane. A fuzzy model called Model 1 is presented for modeling the change of steering angle and speed control by considering time distances with existing cars in these three positions, the information about the speed and direction of car, and the steering angle of car. The behaviors of different drivers under two stress conditions are investigated. Also we obtained two other models based on fuzzy rules called Model 2 and Model 3 by using Sugeno fuzzy inference. Model 2 has two linguistic terms and Model 3 has four linguistic terms for estimating the time distances with other cars. The results of three models are compared. The comparative studies have shown that simulation results are in good agreement with the real world situations.

터널 적용 바형식 반사거울시스템의 채광성능 평가

대부분의 터널 조명은 인공조명에 의존하고 있어 조명설비의 유지관리비 및 전력비를 절감하기 위해 자연채광을 적용한 기초연구가 선행되었다. 이에 본 연구는 터널 조경 바형식 반사거울시스템의 채광성능(조도, 휘도)을 평가하였다. 수평면 조도를 측정한 결과, 전체 평균 1,170 lx로 미설치 대비 6.5배 이상 증가하여 채광유효구간에서 구간별 터널기준조도(KSA 3703)를 만족시키는 것으로 나타났으며, 터널 밖으로 나오는 반대편 차로 운전자의 휘도를 측정하여 분석한 결과, 전체 평균 3.01로 현휘 기준치인 10 이내로 평가되어 눈부심이 발생하지 않는 것으로 나타났다. The basic study was preceded for reducing maintenance and power cost of lighting fixture applying daylighting because most of the tunnel lighting depend on the artificial lighting. This study aims to evaluate the daylighting performance of daylighting performance of bar-type mirror reflector system in tunnel. Illuminance and luminance was measured. As a result of horizontal illuminance measurements, it was satisfied in tunnel recommended illuminance (KSA 3703) that total average was 1,170 lx increased 6.5 times more than this system was not used. Also, as a result of evaluating driver's glare on the opposite lane, glare did not occur and the luminance ratio was 3.01 which satisfies the luminance ratio standard 10.

The Lighting System of the Naname-Kuzebashi Interval of the Hanshin Expressway Kyoto Route(<Special Issue>Traffic Illuminations: Illuminating Futures of Lands, Oceans, and Sky)

Between the Naname-Kuzebashi interval of the Hanshin expressway Kyoto route, it is difficult to conduct maintenance of luminaires for road lighting because the route is road of the opposite lane structure without catwalk on flyover and thus lacks enough space for the maintenance. This difficulty suggests the need for a durable lighting system as well as for efficiency in other maintenance activities (e.g., cleaning). With support from a company we recently contracted with, we developed and initiated a durable and energy-saving lighting system with LED.

Study on Bicycle Signal Timing Algorithm at Signalized Intersection

According to the characteristics of the bicycle traffic flow, the bicycle green time is divided into the maximum queue dissipation time and the time of bicycle cluster center running to the opposite lane, and the formulas are given respectively in this paper. Validation is done based on intersection bicycle data of Beijing city and Tianjin city. Results show that the green time calculated by considering the bicycle cluster meets the interval of bicycles passing through the intersection, which enriches the signal timing algorithm at signalized intersection.

Spontaneous symmetry breaking in a two-lane model for bidirectional overtakingtraffic

Firstly, we consider a unidirectional flux of vehicles, each of which is characterized by its ‘natural’ velocityv drawn from adistribution P(v). The traffic flow is modeled as a collection of straight ‘world lines’ in thetime–space plane, with overtaking events represented by a fixed queuing timeτ imposed on the overtaking vehicle. This geometrical model exhibits platoon formation andallows, among many other things, for the calculation of the effective average velocity of a vehicle of natural velocityv. Secondly, we extend the model to two opposite lanes, A and B. We argue that the queuing timeτ in one lane is determined by the traffic density in the opposite lane. On the basis ofreasonable additional assumptions we establish a set of equations that couple the two lanesand can be solved numerically. It appears that above a critical value of the control parameter the symmetry between the lanes is spontaneously broken: there is a slow lane where longplatoons form behind the slowest vehicles, and a fast lane where overtaking iseasy due to the wide spacing between the platoons in the opposite direction. Avariant of the model is studied in which the spatial vehicle density rather than the flux is the control parameter. Unequal fluxes and in the two lanes are also considered. The symmetry breaking phenomenon exhibited bythis model, even though no doubt hard to observe in pure form in real-life traffic,nevertheless indicates a tendency of such traffic.

Road Course Prediction Using Radar Objects and “Bezier-Splines”

This paper describes an approach to predict the road course with actual measured radar objects combined with an “Adaptive Cruise Control"-System. In the presented algorithm, the objects are divided into four classes: static right of the road, static left of the road, dynamic on the actual lane and dynamic on the opposite lane. On the basis of this classification and some filter methods, the objects of each class are connected by a “Bezier Spline”-Function. For the final road prediction a weighted average of the four actual “Bezier-Splines” is calculated. Compared with other road prediction systems like vision-only approaches, our system is resistant to weather influences and hardly or non visible road markings. Real road tests under various conditions have shown the effectiveness of this approach.

An Intervehicular-Communication Protocol for Distributed Detection of Dangerous Vehicles

Recently, considerable research has been focused on applying ad hoc wireless networking technology to on-the-move vehicles. In this paper, we focus on distributed detection of dangerous vehicles on roads and highways. We propose the dangerous-vehicle-detection protocol (DVDP) to detect drivers who violate the permitted speed limit. In DVDP, each vehicle collects surrounding vehicles' identifications (IDs) and propagates warning information (including its position, speed, time, and collected IDs). This information is then forwarded hop-by-hop using ad hoc communications. A vehicle that receives this information will start to observe its surrounding vehicles. If surrounding vehicles are identified in the received warning information, it will estimate the speed of such vehicles. If the estimated speed exceeds the permitted speed, such vehicles are then marked as ?suspected vehicles,? and the updated warning information is further propagated. By repeating this process, the suspected vehicle (where other vehicles observe the speed violation) will ultimately be marked as a ?dangerous vehicle.? This judgment is then further propagated to warn others and to inform the traffic police. We evaluated the performance of DVDP using a simulator that performs both macroscopic and microscopic traffic simulation, taking into account realistic lane and speed models, mobility, position, and location errors. Simulation results revealed that DVDP's detection probability is greater than 80% when vehicle density is above 40 vehicles/min. When vehicle density is low, deployment of relay points can help to further improve detection probability. In addition, by utilizing vehicles in opposite lanes, detection probability can be further improved.

Judgment in crossing a road between objects coming in the opposite lane

When cars are oncoming in the opposite lane of a road, a driver is able to judge whether his/her car can cross the road at an intersection without a collision with the oncoming cars. We developed a model for the human judgment used to cross a road between oncoming objects. In the model, in order to make the judgment to cross the road, the human visual system compares the time interval it takes for an oncoming object to pass the observer with the time interval it takes for the observer to cross the road. We conducted a psychophysical experiment to test the model prediction. The result showed that human performance is in good agreement with the theoretical consequence provided by the model, suggesting that the human visual system uses not only the visually timed information of the approaching object but also the timed information of self-action for the judgment about crossing the road.

Do cities export biodiversity? Traffic as dispersal vector across urban–rural gradients

ABSTRACTUrban areas are among the land use types with the highes richness in plant species. A main feature of urban floras is the high proportion of non‐native species with often divergent distribution patterns along urban–rural gradients. Urban impacts on plant species richness are usually associated with increasing human activity along rural‐to‐urban gradients. As an important stimulus of urban plant diversity, human‐mediated seed dispersal may drive the process of increasing the similarity between urban and rural floras by moving species across urban–rural gradients. We used long motorway tunnels as sampling sites for propagules that are released by vehicles to test for the impact of traffic on seed dispersal along an urban–rural gradient. Opposite lanes of the tunnels are separated by solid walls, allowing us to differentiate seed deposition associated with traffic into vs. out of the city. Both the magnitude of seed deposition and the species richness in seed samples from two motorway tunnels were higher in lanes leading out of the city, indicating an ‘export’ of urban biodiversity by traffic. As proportions of seeds of non‐native species were also higher in the outbound lanes, traffic may foster invasion processes starting from cities to the surrounding landscapes. Indicator species analysis revealed that only a few species were confined to samples from lanes leading into the city, while mostly species of urban habitats were significantly associated with samples from the outbound lanes. The findings demonstrate that dispersal by traffic reflects different seed sources that are associated with different traffic directions, and traffic may thus exchange propagules along the urban–rural gradient.

分離帯植栽が視界を遮るために生じた事故における管理者の法的責任と管理内容の関係

This research aimed at clarifying proper management of planting demanded from a legal viewpoint. First, Article 2 of State Redress Law was set as keywords, and the judicial precedent was searched, using the internet database law information database LEX/DB Internet. And the examples in connection with the accident which occurred since planting on a central reservation obstructs the field of view were taken up out of the searched examples. And then, the other judicial precedent was supplemented from a certain literature. Finally, four examples were summarized in the table, observing the regarded fact in the decision. As a result, some management to be taken notice of in planting on an open portion of a central reservation newly became clear. It was clarified that administrators have to restrict the height of tree planting on a central reservation to about 60~70cm in the section of the braking distance by the speed limit in the road from an edge outside a pedestrian crossing and that they have to manage tree planting based on the traffic situation of the road, grasping the situation of the visibility to the opposite lane also in other roads.

Subjective sleepiness and accident risk avoiding the ecological fallacy

The present study of sleepiness and accident risk in a HI-FI car simulator aimed to provide subject-level relative risks (RR) with 95% confidence intervals (CI) for different levels of subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS), 1 = very alert, 9 = very sleepy, fighting sleep, an effort to staying awake. Five male and five female shift workers, mean age 37 years, participated with a 2-h drive (08:00-10:00 hours) in a dynamic high-fidelity moving base driving simulator, after a night of work and after a night of sleep. Subjective sleepiness was measured with KSS every 5 min and events of incidents (two wheels outside the right lane), accidents (two wheels off the road or four wheels in opposite lane) and crashes (four wheels off the road) were recorded. The probability of an accident was modelled with a Generalized Linear Mixed Model approach to estimate subject-specific effects, rather than group average effects, to avoid the ecological fallacy. The results showed that sleepiness was strongly related to accident risk. An average subject was estimated at 28.2 times (95% CI RR = 10.7-74.1) increased risk at KSS = 8 and at 185 times (95% CI RR = 42-316) at KSS = 9 compared with KSS = 5. There were large individual differences in event propensity that complicates the prediction of absolute accident risk for individual subjects.