The existence and impact of the Psychological Refractory Period effect in the driving environment

Driver distraction from in-vehicle tasks can have negative impacts on longitudinal and lateral vehicle control. The distraction problem is increasing due to advances in the functionality, availability, and number of in-vehicle systems. One approach to a solution is managing in-vehicle task presentation to reduce associated distraction. This paper reports three driving simulator experiments, designed to investigate the existence of the Psychological Refractory Period in the driving context and its effect on driver performance. The first two studies demonstrate that the effect is present when one or two surrogate in-vehicle tasks are presented in close temporal proximity to a lead vehicle braking event. Brake responding is subject to an increasing delay as the interval to an in-vehicle task is decreased. In-vehicle task modality and task presentation order modulate this effect. The final study will investigate whether the Psychological Refractory Period exists for a range of safety-critical driving events such as lead vehicle decelerations, swerving away from an out-of-control vehicle, and performing a lane-change manoeuvre. The advances on prior work include the use of an advanced driving simulator, and presentation of unpredictable safety-critical events and real-world in-vehicle tasks. The results have implications for the management of in-vehicle distractions – and driver safety; specifically through controlling the timing and modality of task presentation

Usability testing of three visual HMIs for assisted driving: How design impacts driver distraction and mental models.

There is a variety of visual human-machine interfaces (HMI) designed across vehicle manufacturers that support drivers while supervising driving automation features, such as adaptive cruise control (ACC). These various designs communicate the same limited amount of information to drivers about their ACC system and it is unclear which HMI designs impact driver distraction the least or how their design could be modified to help drivers develop more accurate mental models of their ACC system. Using a user-centred design (UCD) approach, we designed a speedometer to inform drivers about some of the system’s capabilities and then invited 23 drivers to use ACC in a low-fidelity driving simulator to compare the usability of three HMIs using eye-tracking, response times, and qualitative data. Our attempt at designing an intuitive and more informative speedometer received mixed results, but design recommendations are given regarding the indication of the set target speed, set time gap between vehicles (headway distance), and system mode (conventional or adaptive cruise). Practitioner summary: Manufacturers’ heterogeneous designs of their visual HMIs for the ACC systems may impact driver distraction in different ways. We used usability testing to compare three HMIs in a driving simulator and make several design recommendations to indicate speed, time gap, and system mode in a more efficient way. Abbreviations: ACC: adaptive cruise control; ADAS: advanced driving assistance system; HMI: human-machine interface; ISO: international organisation for standardization; OEM: original equipment manufacturer; RSME: rating scale of mental effort; RT: response time; R-TLX: raw task load index; SUS: system usability scale; TGT: total glance time; UCD: user-centred design; UX: user experience; xTGT: extended total glance tim

How can humans understand their automated cars? HMI principles, problems and solutions

As long as vehicles do not provide full automation, the design and function of the Human Machine Interface (HMI) is crucial for ensuring that the human “driver” and the vehicle-based automated systems collaborate in a safe manner. When the driver is decoupled from active control, the design of the HMI becomes even more critical. Without mutual understanding, the two agents (human and vehicle) will fail to accurately comprehend each other’s intentions and actions. This paper proposes a set of design principles for in-vehicle HMI and reviews some current HMI designs in the light of those principles. We argue that in many respects, the current designs fall short of best practice and have the potential to confuse the driver. This can lead to a mismatch between the operation of the automation in the light of the current external situation and the driver’s awareness of how well the automation is currently handling that situation. A model to illustrate how the various principles are interrelated is proposed. Finally, recommendations are made on how, building on each principle, HMI design solutions can be adopted to address these challenges

Intelligent speed adaptation: accident savings and cost–benefit analysis

The UK External Vehicle Speed Control project has made a prediction of the accident savings with Intelligent Speed Adaptation, and estimated the costs and benefits of national implementation. The best prediction of accident reduction was that the fitting on all vehicles of a simple mandatory system, with which it would be impossible for vehicles to exceed the speed limit, would save 20% of injury accidents and 37% of fatal accidents. A more complex version of the mandatory system, including a capability to respond to current network and weather conditions, would result in a reduction of 36% in injury accidents and 59% in fatal accidents. The implementation path recommended by the project would lead to compulsory usage in 2019. The cost benefit analysis carried out showed that the benefit-cost ratios for this implementation strategy were in a range from 7.9 to 15.4, i.e. the payback for the system could be up to 15 times the cost of implementing and running it

Driving Simulators as Research Tools in Traffic Psychology

Research driving simulators, as opposed those employed in the development of driver training, are primarily used to facilitate scientific evaluations of driver behaviour. They enjoy many benefits over naturalistic studies using instrumented vehicles with their main advantage being a considerable versatility to configure virtual scenarios that exactly match the requirement of a particular investigation. Environmental conditions can be manipulated such as day/night operation, weather conditions and state of the road surface. The parameters of the driven vehicle can be altered: for example suspension design, tyre construction and steering characteristics can be matched to an existing or prototype vehicle. New and novel road schemes, methods of signage and highway infrastructure can be modelled virtually and evaluated prior to the logistical challenge of modifying large areas of roadway. Furthermore, there is the ethical advantage of an inherently safe environment for the participants of a particular study. This chapter discusses these merits along with the disadvantages of the use of driving simulators in driver behavioural research

Managing in-vehicle distractions: evidence from the psychological refractory period paradigm

Driver distraction by in-vehicle tasks has a negative impact on driving performance and crash risk. This paper describes a study investigating the effect of interacting with a surrogate in-vehicle system task -- requiring a two-choice speeded response -- in close temporal proximity to a subsequent lead vehicle braking event. The purpose of the study was to determine the 'task-free' interval required before a braking event to ensure safe braking performance. Drivers (N = 48) were split into six groups and randomly assigned an in-vehicle task defined by stimulus (three levels) and response modality (two levels). Four blocks of intermixed single- and dual-task trials were presented. The time interval between the two tasks was varied on dual-task trials. Slower braking responses on dual-task trials relative to single-task trials indicated dual-task interference. Driver braking performance demonstrated the psychological refractory period effect -- an increase in reaction time with decreasing temporal separation of the two tasks. The impact of in-vehicle task stimulus and response modality on performance is discussed in relation to predictions based on Multiple Resource Theory. This study demonstrates a fundamental human performance limitation in the real-world driving context and has implications for driver response speeds when distracted. Specifically, the presentation of an in-vehicle task in the 350 milliseconds before a braking event could have severe safety consequences. The use of the findings to manage in-vehicle stimulus presentation is discussed. Problems with implementation of the results are reported

Intelligent traffic signals for pedestrians: evaluation of trials in three countries

The DRIVE II project VRU-TOO (Vulnerable Road User Traffic Observation and Optimization) carried out trials of innovative pedestrian signalized crossings that were designed to be more responsive to pedestrians needs and thereby improve pedestrian safety and comfort. These advanced crossings were installed at sites in three European countries and a comprehensive evaluation of the impacts was carried out, with particular emphasis on changes in pedestrian behaviour and safety. While there were important differences in the impacts at the various sites, partly reflecting differences in system implementation, there were general gains in safety and comfort for pedestrians. These improvements were obtained without major side effects on vehicle travel. (C) 1999 Elsevier Science Ltd. All rights reserved