Driver performance modelling and its practical application to railway safety

This paper reports on the development and main features of a model of driver information processing. The work was conducted on behalf of Network Rail to meet a requirement to understand and manage the driver's interaction with the infrastructure through lineside reminder appliances. The model utilises cognitive theory and modelling techniques to describe driver performance in relation to infrastructure features and operational conditions. The model is capable of predicting the performance time, workload and error consequences of different operational conditions. The utility of the model is demonstrated through reports of its application to the following studies:

Research on the effect of line speed on driver interaction with signals and signs.

Calculation of minimum reading times for signals.

Development of a human factors signals passed at danger (SPAD) hazard checklist, and a method to resolve conflicts between signal sighting solutions.

Research on the demands imposed on drivers by European train control system (ETCS) driving in a UK context.

The paper also reports on a validation of the model's utility as a tool for assessing cab and infrastructure drivability.     

Quantitative modelling in cognitive ergonomics: predicting signals passed at danger

Abstract

This paper shows how to combine field observations, experimental data and mathematical modelling to produce quantitative explanations and predictions of complex events in human–machine interaction. As an example, we consider a major railway accident. In 1999, a commuter train passed a red signal near Ladbroke Grove, UK, into the path of an express. We use the Public Inquiry Report, ‘black box’ data, and accident and engineering reports to construct a case history of the accident. We show how to combine field data with mathematical modelling to estimate the probability that the driver observed and identified the state of the signals, and checked their status. Our methodology can explain the SPAD (‘Signal Passed At Danger’), generate recommendations about signal design and placement and provide quantitative guidance for the design of safer railway systems’ speed limits and the location of signals.

Practitioner Summary: Detailed ergonomic analysis of railway signals and rail infrastructure reveals problems of signal identification at this location. A record of driver eye movements measures attention, from which a quantitative model for out signal placement and permitted speeds can be derived. The paper is an example of how to combine field data, basic research and mathematical modelling to solve ergonomic design problems.     

Driver behaviour at rail level crossings: responses to flashing lights, traffic signals and stop signs in simulated rural driving

Australian road and railway authorities have made a concerted effort to reduce the number of rail level crossings, particularly the higher risk passive crossings that are protected by devices such as ‘give way’ or ‘stop’ signs. To improve this situation, passive level crossings are often upgraded with active controls such as flashing red lights. Traffic signals may provide good safety outcomes at level crossings but remain untested. The primary purpose of this research was to compare driver behaviour at two railway level crossings with active controls, flashing red lights and traffic signals, to behaviour at the current standard passive level crossing control, a stop sign. Participants drove the MUARC advanced driving simulator for 30 min. During the simulated drive, participants were exposed to three level crossing scenarios. Each scenario consisted of one of three level crossing control types, and was associated with an oncoming train. Mean vehicle speed on approach to the level crossings decreased more rapidly in response to flashing lights than to traffic signals. While speed on approach was lowest for the stop-sign condition, the number of non-compliant drivers (i.e., those who did not stop) at the crossing was highest for this condition. While results indicate that traffic signals at rail level crossings do not appear to offer any safety benefits over and above flashing red lights, further avenues of research are proposed to reach more definitive conclusions. Compliance was lowest for the passive crossing control which provides further support for the ongoing passive crossing upgrades in Australia.     

An investigation of train driver visual strategies

Train driving is primarily a visual task; train drivers are required to monitor the dynamic scene visually both outside and inside the train cab. Poor performance on this visual task may lead to errors, such as signals passed at danger. It is therefore important to understand the visual strategies that train drivers employ when monitoring and searching the visual scene for key items, such as signals. Prior to this investigation, a pilot study had already been carried out using an eye tracking technique to investigate train drivers’ visual behaviour and to collect data on driver monitoring of the visual environment, Groeger et al. (2003) Pilot study of train drivers’ eye movements, University of Surrey. However, a larger set of data was needed in order to understand more fully train driver visual behaviour and strategies. In light of this need, the Transport Research Laboratory produced a methodology for the assessment of UK train driver visual strategies, on behalf of the Rail Safety and Standards Board and applied this methodology to conduct a large-scale trial. The study collected a wealth of data on train drivers’ visual behaviour with the aim of providing a greater understanding of the strategies adopted. The corneal dark-eye tracking system chosen for these trials tracks human visual search and scanning patterns, and was fitted to 86 drivers whilst driving in-service trains. Data collected include the duration and frequency of glances made towards different elements of the visual scene. In addition, the train drivers were interviewed after driving the routes, to try and understand the thought processes behind the behaviour observed. Statistical analysis of over 600 signal approaches was conducted. This analysis revealed that signal aspect, preceding signal aspect, signal type and signal complexity are important factors, which affect the visual behaviour of train drivers. Train driver interview data revealed that driver expectation also plays a significant role in train driving. The findings of this study have implications for the rail industry in terms of infrastructure design, design of the driving task and driver training. However, train driving is extremely complex and the data from this study only begin to describe and explain train driver visual strategies in the specific context of signal approaches. This study has provided a wealth of data and further analysis of it is needed to investigate the role of other factors and the complex relationships between factors during signal approaches and other driving situations systematically. Finally, there are important aspects of visual behaviour that cannot be examined using these data or this method. Investigation of other aspects of visual behaviour, such as peripheral vision, will require other methods such as simulation.     

Effects of text space of Chinese-English bilingual traffic sign on driver reading performance

Chinese-English bilingual traffic signs (CEBTS) are widely applied in public spaces within China, but few studies have addressed the spatial arrangement of the two languages on CEBTS and road standards provide little guidance for it. This study investigates whether changes in ‘separating space’, the vertical space between bilingual place names on CEBTS, affects driver reading performance. Ten sign combinations were developed using variations in the sign’s graphic complexity, total number of place names, and the spatial distribution of the place names. Each sign was displayed in a 3D graphics rendered clip of someone driving towards the road sign in random order. Participants identified destinations by reading the signs shown in the clip. The speed and the accuracy of responses was recorded. 39 English-reader participants were recruited and equally split into three groups. Three levels of separating space 0.5H, 0.75H and 1H; H refers to one Chinese character height, were prepared according to a between-subject factorial design. The results show that the separating space affected the response time regardless of sign combinations. Both 0.5H and 0.75H separations caused significant faster reading time and higher accuracy than 1H, but 0.75H appears to achieve better result. The findings contribute to the legibility research concerning bilingual signs with two very different character sets. This study considers improving sign legibility through spatial arrangement of the bilingual text, which is currently limited in the field of Chinese road sign legibility. The findings could inform future standards for Chinese-English road signs.     

Multiobjective shape optimization of speed humps

This paper presents a new approach to the shape optimization of road speed humps. The proposed approach is based on multiobjective genetic optimization of the hump profile while taking into account the separation phenomenon, which occurs when the front tires of the vehicle momentarily lose contact with the road surface. The optimization is carried out for speeds up to twice the authorized speed (throughout this article, the term authorized speed refers to speed limits enforced in speed reduction [bump] areas of the roads) rather than for illegally high speeds as adopted by many of the previous works. A 6-degree of freedom non-linear dynamic model is used to identify the speeds at which separation occurs, and hump profiles associated with these speeds are discarded as infeasible solutions. Three independent objective functions are selected for optimization. They include the maximum vertical acceleration experienced by the driver when crossing the hump below the authorized speed limit (to be minimized), the same vertical acceleration at speeds above the authorized speed (to be maximized), and the ascending ratio of the “speed—vertical acceleration” curve (to be maximized). These objective functions are evaluated for more than 10,000 humps of two popular profile types (sinusoidal and flat top with straight ramps) and optimum profiles for three speed limits of 20, 25, and 30km/h are determined using the multiobjective nondominated sorting genetic algorithm II. As a result, a Pareto front of at least ten optimal points is achieved for each of the two hump profile types. Furthermore, to incorporate the economical aspects of the real-world problem, Pareto optimal points for the two profile types were compared based on their lateral section areas (an indication of the manufacturing cost). The comparison shows that sinusoidal humps more often than not outdo their flat top rivals economically.     

Evaluating the effects of bilingual traffic signs on driver performance and safety

Variable message signs (VMS) can provide immediate and relevant information to road users and bilingual VMS can provide great flexibility in countries where a significant proportion of the population speak an alternative language to the majority. The study reported here evaluates the effect of various bilingual VMS configurations on driver behaviour and safety. The aim of the study was to determine whether or not the visual distraction associated with bilingual VMS signs of different configurations (length, complexity) impacted on driving performance. A driving simulator was used to allow full control over the scenarios, road environment and sign configuration and both longitudinal and lateral driver performance was assessed. Drivers were able to read one- and two-line monolingual signs and two-line bilingual signs without disruption to their driving behaviour. However, drivers significantly reduced their speed in order to read four-line monolingual and four-line bilingual signs, accompanied by an increase in headway to the vehicle in front. This implies that drivers are possibly reading the irrelevant text on the bilingual sign and various methods for reducing this effect are discussed.     

Evaluating the effects of bilingual traffic signs on driver performance and safety

Variable message signs (VMS) can provide immediate and relevant information to road users and bilingual VMS can provide great flexibility in countries where a significant proportion of the population speak an alternative language to the majority. The study reported here evaluates the effect of various bilingual VMS configurations on driver behaviour and safety. The aim of the study was to determine whether or not the visual distraction associated with bilingual VMS signs of different configurations (length, complexity) impacted on driving performance. A driving simulator was used to allow full control over the scenarios, road environment and sign configuration and both longitudinal and lateral driver performance was assessed. Drivers were able to read one- and two-line monolingual signs and two-line bilingual signs without disruption to their driving behaviour. However, drivers significantly reduced their speed in order to read four-line monolingual and four-line bilingual signs, accompanied by an increase in headway to the vehicle in front. This implies that drivers are possibly reading the irrelevant text on the bilingual sign and various methods for reducing this effect are discussed.     

Personnel scheduling in a complex logistic system: a railway application case

In complex logistic systems, such as transportation systems, dealing with personnel scheduling is a non-trivial task. Duties have to be created and assigned to workers in a way to optimize a certain objective function. In this paper, in particular, we consider the case of scheduling train drivers on a railway subnetwork. Train driver scheduling involves the construction of feasible duties from a set of trips to be carried out by a number of train drivers. Each duty consists of a sequence of trips to be carried out by a single train driver on a single day. The duties should be such that: each trip is covered by at least one duty, each duty satisfies feasibility constraints, additional constraints involving the complete schedule are satisfied, one or several objectives are met. In this paper we focus on minimizing the number of duties and on maximizing the robustness of the obtained schedule for outside disruptions. We present an implicit column generation solution approach. We describe a heuristic procedure to find an initial feasible solution together with a heuristic branch-and-price algorithm based on a dynamic programming algorithm for the pricing-out of columns. We tested our approach on the timetable of the Intercity train series 500, 700, 1600 and 1700 of NS Reizigers, the largest Dutch operator of passengers trains.     

The ergonomics of road signs: explicit and embedded speed limits

The European traffic sign system encodes the meaning of a sign by use of varying forms, colours and symbols. However, signs differ greatly in how explicit their message is. Thus, the meaning of most direction signs is self-evident, while that of some others is less obvious. The European built-up area sign limits driving speed to 50 km/h, like speed limit signs, but its rectangular form and symbol not associated with speed limit distinguish it clearly from standard speed limit signs. Also, the function of the built-up area sign is more complex than the one of speed limit signs: the built-up area sign both limits speed and informs about entering a built-up area. The purpose of this study was to investigate whether the built-up area sign is noticed and obeyed as well as speed limit signs. In three field experiments the 50 km/h, 80 km/h signs and built-up area signs were alternated and speed changes were measured. Results indicated that the built-up area signs elicit only negligible speed responses compared to the speed limit signs while supervision (visible police car) results in a similar effect for both signs. The same results were also obtained in the laboratory where slides about traffic situations were shown to subjects who were asked if it was necessary to decelerate. These findings suggested that, in contrast to the built-up area sign, drivers have developed a mental model which facilitates more effective noticing of speed limit signs. The built-up sign does not share these facilitating effects, because of its dual function and symbol and form which are not associated with speed limits.     

Motion extrapolation of auditory–visual targets

Many tasks involve the precise estimation of speed and position of moving objects, for instance to catch or avoid objects that cohabit in our environment. Many of these objects are characterised by signal representations in more than one modality, such as hearing and vision. The aim of this study was to investigate the extent to which the simultaneous presentation of auditory and visual signals enhances the estimation of motion speed and instantaneous position. Observers are asked to estimate the instant when a moving object arrives at a target spatial position by pressing a response button. This task requires observers to estimate the speed of the moving object and to calibrate the timing of their manual response such that it coincides with the true arrival time of the moving object. When both visual and auditory motion signals are available, the variability in estimating the arrival time of the moving object is significantly reduced compared to the variability in the unimodal conditions. This reduction in variability is consistent with optimal integration of the auditory and visual speed signals. The average bias in the estimated arrival times depends on the motion speed: for medium speeds (17 deg/s) observers’ subjective arrival times are earlier than the true arrival times; for high speeds (47 deg/s) observers exhibit a (much smaller) bias in the other direction. This speed-dependency suggests that the bias is due to an error in estimating the motion speeds rather than an error in calibrating the timing of the motor response. Finally, in this temporal localization task, the bias and variability show similar patterns for motion defined by vision, audition or both.     

Efficient formalization of railway interlocking data in RailML

Railways wish to reduce the costs of engineering interlocking systems by simplifying the exchange of technical information between stakeholders. Exchanging interlocking data in a machine-readable and standardized format removes inefficiency due to misinterpretation and conversion of data from non-standard, often paper-based formats. This paper proposes an UML class representation of the interlocking data that maps the characteristics of the interlocking system. These data model represents both tabular and geographical interlocking. The model reflects the topology of the railway network that the interlocking controls, routes, relations between signal aspects, speed indication signals, automatic train protection (ATP) and the state of movable and non-movable track elements. The data are machine-readable RailML, an incarnation of XML that is gaining the status of standard in railway modelling. We applied our approach to model the Dutch Santpoort Noord station, starting from paper-based track and signal plans. The resulting database captures all the features of the interlocking, whilst removing data redundancy. The model has general validity and it is easily extendible to other interlocking and ATP systems. Our approach contributes to create standard, electronic interlocking databases, directly from technical documents currently used in the practical world.     

应用EMD熵和ReliefF分析高铁横向减振器故障

横向减振器是转向架的关键部件,其作用是衰减车体与转向架间的振动,其性能对列车的舒适性和安全性有重要影响。横向减振器的故障会引起列车车体振动信号的变化,为了能对其进行性能监测和故障诊断,提出一种基于EMD排列组合熵和ReliefF的特征分析方法。先对预处理过的信号进行EMD分解,后对得到的若干个包含主要故障信息的本征模式函数求解熵值,最后用ReliefF对6阶本征模式函数熵值构成的特征矢量进行优化降维,对降维后的特征用支持向量机对四种工况进行分类识别。实验结果表明,对运行速度200 km/h及以上时的平均识别率可以达到96%以上。     

高帧频CCD驱动电路设计

为了实现由Kodak KAI0340D CCD（Charge Coupled Device）组成的新型图像采集系统,需要设计专门的CCD时序驱动电路。使用Xilinx Spartan3AN FPGA（Field Programmable Gate Arrays）设计时序产生电路,经过驱动芯片MAX4426和ISL55110驱动,再经过箝位电路箝位,得到了满足CCD要求幅度和时序的驱动信号。经实验验证该方法产生了满足CCD要求的驱动时序,实际测试时CCD帧频达到了205.6frame/s。     

A driving-emulation task to study the integration of goals with obligatory and prohibitory traffic signs

This research aims to analyse how drivers integrate the information provided by traffic signs with their general goals (i.e. where they want to go). Some previous studies have evaluated the comparative advantages of obligatory and prohibitory traffic signs using a judgement task. In this work, a new experimental task with greater similarity to driving situations is proposed. Participants imagine they are driving a vehicle and must make right or left turn manoeuvres according to a previously indicated objective and the information from obligatory and prohibitory traffic signs. Eighty-two participants took part in two different experiments. According to the results, an obligatory traffic sign is associated with faster and more accurate responses only when the participant's initial objective is allowed. When the initial objective was not allowed, an advantage in accuracy was observed with prohibitory traffic signs and there was no significant difference in reaction time between the two types of sign. These results suggest that having an obligatory traffic sign may facilitate a correct response when the driver's goal is effectively allowed, whereas a prohibitory traffic sign could be more effective in preventing error when the driver has a not-allowed goal in mind. However, processing a prohibitory sign requires an extra inference (i.e. deciding which is the allowed manoeuvre), and thus the potential advantage in reaction time of the prohibitory sign may disappear. A second experiment showed that the results could not be explained by a potential congruency effect between the location (left or right) of the road signs and the position of the key or the hand used to respond (such as the Simon effect or the spatial Stroop effect). Also, an increase in the difficulty of the task (using an incongruent hand to respond) affected performance more strongly in experimental conditions that required making inferences. This made the advantage of the obligatory sign over the prohibitory sign in this condition more noteworthy. The evidence gathered in the current study could be of particular interest in some applied research areas, such as the assessment of road traffic signalling strategies or the ergonomic design of GPS navigation systems.     

Effects of apparent image velocity and complexity on the dynamic visual field using a high-speed train driving simulator

Train driving is a highly visual task. The visual capabilities of the train driver affects driving safety and driving performance. Understanding the effects of train speed and background image complexity on the visual behavior of the high-speed train driver is essential for optimizing performance and safety. This study investigated the role of the apparent image velocity and complexity on the dynamic visual field of drivers. Participants in a repeated-measures experiment drove a train at nine different speeds in a state-of-the-art high-speed train simulator. Eye movement analysis indicated that the effect of image velocity on the dynamic visual field of high-speed train driver was significant while image complexity had no effect on it. The fixation range was increasingly concentrated on the middle of the track as the speed increased, meanwhile there was a logarithmic decline in fixation range for areas surrounding the track. The extent of the visual search field decreased gradually, both vertically and horizontally, as the speed of train increased, and the rate of decrease was more rapid in the vertical direction. A model is proposed that predicts the extent of this tunnel vision phenomenon as a function of the train speed.Relevance to industryThis finding can be used as a basis for the design of high-speed railway system and as a foundation for improving the operational procedures of high-speed train driver for safety.     

Do in-vehicle advanced signs enhance older and younger drivers’ intersection performance? Driving simulation and eye movement results

An experimental study was conducted to determine if intersection behaviour benefited from advanced in-vehicle signs presented to older and younger drivers in a head-up display (HUD) format. The University of Calgary Driving Simulator (UCDS) was used to evaluate intersection performance. Measures of those who were able to stop or ran the yellow light, speed over the span of the intersection, perception response time, and eye movements were analyzed to determine if performance improved or whether undesirable adaptive behaviours occurred. In-vehicle signs facilitated an increase in the frequencies of stopping for both younger and older drivers at intersections with relatively short yellow onsets. The speed at the yellow light onset for both those who stopped and those who proceeded through the intersection was reduced by the presence of the in-vehicle signs. The primary behavioral influence of the in-vehicle signs was to cause the drivers’ to reduce their velocity in advance of an intersection. Eye movement analyses indicated that younger drivers looked at the in-vehicles signs more often and for longer overall durations than older drivers. Older drivers had slower intersection approach speeds, stopped more accurately, and were more likely to not clear the intersection before the traffic light turned to an all-red phase than younger drivers. The implications of the in-vehicle sign results are discussed in terms of in-vehicle information systems (IVIS) design guidelines and evaluation methods.     

Effects of speed, load and damping on the dynamic response of railway bridges and vehicles

In this paper, the effects of various parameters influencing the dynamic response of railway bridges are investigated. A versatile and computationally efficient numerical model was developed for this purpose. The model incorporates three-dimensional multi-body train and finite element bridge subsystems. The corresponding equations of motion are integrated numerically by applying the Newmark’s method combined with a modified Newton-Raphson iterative procedure. The model was verified by comparisons with analytical and numerical solutions available in the literature and good agreement was found. A parametric analysis was carried out to establish the key variables influencing the dynamic response of railway bridges. The speed of the train, train-to-bridge frequency, mass and span ratios, as well as bridge damping were identified as significant variables. Vehicle damping was found to have negligible influence on bridge response. Particularly strong dynamic amplification was found for train with shortly and regularly spaced axles travelling at the critical speeds. Other general conclusions were drawn on the basis of the parametric study.     

实时矩形交通限速标志识别系统

交通限速标志识别系统是汽车辅助驾驶系统的一项重要组成部分,本文提出了一种实时矩形交通标志识别系统.首先采用多尺度多区域的局部二值模式（LBP）特征训练Adaboost分类器进行交通限速标志的检测,然后利用线性预测的算法进行标志跟踪.识别预处理阶段,首先采用投影分析的方法对交通标志进行旋转校正,然后采用基于积分图的自适应二值化方法将图像进行二值化,再利用连通区域标记方法得到包含限速标志数字的最小矩形区域.识别时首先采用主元分析（PCA）进行特征向量提取,然后用聚类的方法构建二叉树的线性支持向量机进行分类识别.在普通笔记本电脑系统配置下,通过大量的实际道路场景的视频数据测试,系统取得了98.3%的正确识别率,平均处理速度达16帧/s.     

基于小波神经网络的数字信号调制识别

本文采用熵特征的提取方法,大大减小了特征值的计算量,增强了小波神经网络(WNN)识别的有效性。同时采用改进的算法训练小波神经网络,有效的避免算法陷入局部最小值,克服了传统BP网络的固有缺点,并提高了小波神经网络的训练速度。结果表明,该系统能快速有效的识别出数字信号的调制类型,具有较高的识别精度。