Toward a Holistic Communication Approach to an Automated Vehicle's Communication With Pedestrians: Combining Vehicle Kinematics With External Human-Machine Interfaces for Differently Sized Automated Vehicles

Future automated vehicles (AVs) of different sizes will share the same space with other road users, e. g., pedestrians. For a safe interaction, successful communication needs to be ensured, in particular, with vulnerable road users, such as pedestrians. Two possible communication means exist for AVs: vehicle kinematics for implicit communication and external human-machine interfaces (eHMIs) for explicit communication. However, the exact interplay is not sufficiently studied yet for pedestrians' interactions with AVs. Additionally, very few other studies focused on the interplay of vehicle kinematics and eHMI for pedestrians' interaction with differently sized AVs, although the precise coordination is decisive to support the communication with pedestrians. Therefore, this study focused on how the interplay of vehicle kinematics and eHMI affects pedestrians' willingness to cross, trust and perceived safety for the interaction with two differently sized AVs (smaller AV vs. larger AV). In this experimental online study (N = 149), the participants interacted with the AVs in a shared space. Both AVs were equipped with a 360° LED light-band eHMI attached to the outer vehicle body. Three eHMI statuses (no eHMI, static eHMI, and dynamic eHMI) were displayed. The vehicle kinematics were varied at two levels (non-yielding vs. yielding). Moreover, “non-matching” conditions were included for both AVs in which the dynamic eHMI falsely communicated a yielding intent although the vehicle did not yield. Overall, results showed that pedestrians' willingness to cross was significantly higher for the smaller AV compared to the larger AV. Regarding the interplay of vehicle kinematics and eHMI, results indicated that a dynamic eHMI increased pedestrians' perceived safety when the vehicle yielded. When the vehicle did not yield, pedestrians' perceived safety still increased for the dynamic eHMI compared to the static eHMI and no eHMI. The findings of this study demonstrated possible negative effects of eHMIs when they did not match the vehicle kinematics. Further implications for a holistic communication strategy for differently sized AVs will be discussed

Understanding interactions between autonomous vehicles and other road users: A literature review

This review draws on literature relating to the interactions of vehicles with other vehicles, interactions between vehicles and infrastructure, and interactions between autonomous vehicles and cyclists and autonomous vehicles and pedestrians. The available literature relating to autonomous vehicles interactions is currently limited and hence the review has considered issues which will be relevant to autonomous vehicles from reading and evaluating a broader but still relevant literature.The project is concerned primarily with autonomous vehicles within the urban environment and hence the greatest consideration has been given to interactions on typical urban roads, with specific consideration also being given to shared space. The central questions in relation to autonomous vehicles and other road users revolve around gap acceptance, overtaking behaviour, behaviour at road narrowings, the ability to detect and avoid cyclists taking paths through a junction which conflict with the autonomous vehicle’s path, and the ability of autonomous vehicles to sense and respond to human gestures. A long list of potential research questions has been developed, many of which are not realistically answerable by the Venturer project. However, the important research questions which might potentially be answered by the current project are offered as the basis for the more detailed consideration of the conduct of the interaction trial

Gap acceptance study of pedestrians crossing between platooning autonomous vehicles in a virtual environment

Autonomous vehicles (AVs) operating in shared urban environments, often referred to as “pods”, will constantly have to interact with pedestrians. As a result, an effective strategy will be required for pods to continue operating, while in close proximity to people. This strategy could be in terms of active negotiation, where a pod identifies a person and gives way; or a more passive strategy, such as requiring pods to travel close together in platoons, in order to reduce the number of individual vehicle encounters. For this latter example, it is critical to understand how the spaces between pods and AVs in general are perceived by pedestrians, and what factors will persuade and dissuade crossing. Therefore, this paper seeks to understand this relationship, and presents results from a pedestrian gap acceptance study for platoons. To ensure the safety of participants, a virtual environment was used instead of real vehicles. The goal of the experiment described in this paper, is to understand the gap acceptance behaviour of participants, when presented with a platoon of pods in different environments. The experiment evaluated four vehicle speeds, from 1 km/h to 16 km/h, four temporal gaps, from 2 s to 5 s, and two environments. These environments were a typical road layout, with footpath and line markings, and a shared space, where all markings and separation between pod and pedestrian were removed. For each scenario, participants were asked if they would cross between the pods and how safe they felt about the situation, recorded as a Likert score. The results suggest that people are more likely to attempt to cross between a platoon of pods when they are travelling closer together in a shared space (no line markings or separation between vehicles and pedestrian), compared to a road environment (separated by raised pavement and road markings). However, it was also found that people’s subjective rating of safeness was higher in the road environment, when presented with a platoon of pods, compared to the shared space

Psychological Mechanisms in Pedestrian Road Crossing Behaviour: Observations and Models

As automated vehicles (AVs) become advanced, there is a growing concern over how AVs should interact with pedestrians. Increasing attention has, therefore, been drawn to pedestrian crossing behaviour research. Given the complexity of human behaviour and the traffic environment, existing studies have identified many influential factors related to pedestrian crossing behaviour. An important problem, however, is the need for more effort to uncover the human psychological mechanisms underpinning these observed behavioural patterns. Hence, the key aim of this project is: to narrow the gap between psychology and pedestrian crossing behaviour by bringing ideas from psychology into the analysis of pedestrian crossing behaviour and modelling this behaviour from a psychological perspective. This doctoral project conducted a range of research, including experimental study and empirical data analyses, to investigate pedestrian crossing behaviour in different traffic scenarios, i.e., uncontrolled intersections with a constant-speed vehicle, constant-speed continuous traffic flow, or a yielding vehicle. It was found that visual looming theta_dot (the rate of change of the optical size of the vehicle on the pedestrian's retina) is significantly negatively related to the percentage of crossing gap acceptance in constant-speed scenarios, supporting that looming may cause a sense of collision threat that affects pedestrian crossing decisions. In vehicle-yielding scenarios, the empirical data indicated that another looming-related visual cue tau_dot (the rate of change of tau, tau=theta/theta_dot) is a potential visual cue for detecting vehicle-yielding behaviour. A hybrid perception framework was then developed to account for pedestrian crossing behaviour by combining both theta_dot and tau_dot. In continuous constant-speed traffic flow scenarios, it was found that pedestrians might dynamically adjust their crossing decisions by comparing theta_dot of the previously rejected gap, the currently faced gap, and the following gap. Based on these findings, this project developed models to characterise both pedestrian crossing decision and its time-dynamic nature. Crucially, validations across different datasets demonstrated that these models reproduce pedestrian crossing decisions qualitatively and quantitatively. Predictions from these models highlight the notion that looming-related visual cues are directly available to the pedestrian visual system. Finally, in addition to these psychological mechanisms and models, this project also provided novel observations in pedestrian crossing behaviour. It suggested that the behaviour of pedestrians tending to accept smaller gaps at higher vehicle speed conditions might lead to potential safety issues for pedestrians. Distracted pedestrians might self-regulate their engagement between the crossing task and distraction based on the traffic situation in the continuous traffic flow, such as time gap size. Moreover, in a vehicle behaviour estimation study, it was found that in the early stage of road-crossing scenarios, pedestrians tended to interpret low driving speeds as a signal to give way, regardless of whether the vehicle was slowing down. Overall, understanding pedestrian road-crossing behaviour and its underlying mechanisms is a difficult challenge. Beyond purely experimental research and data analysis, this project demonstrates that applying theories and models developed in psychology will bring considerable benefits to pedestrian road-crossing behaviour research

Comparing state-of-the-art and emerging augmented reality interfaces for autonomous vehicle-to-pedestrian communication

In the last few years, a considerable literature has grown around the theme of how to provide pedestrians and other vulnerable road users (VRUs) with a clear indication about a fully autonomous vehicle (FAV)'s status and intentions, which is crucial to make FAVs and VRUs coexist. So far, a variety of external interfaces leveraging different paradigms and technologies have been created. Proposed designs include vehicle-mounted devices (like LED panels), short-range on-road projection, and road infrastructure interfaces (e.g., special asphalts with embedded displays). These designs have been experimented in different settings, using mockups, specially prepared vehicles, or virtual environments, with heterogeneous evaluation metrics. Some promising interfaces based on Augmented Reality (AR) have been proposed too, but their usability and effectiveness have not been tested yet. This paper aims to complement such body of literature by presenting a comparison of state-of-the-art interfaces and new designs under common conditions. To this aim, an immersive Virtual Reality-based simulation was developed, recreating a well-known scenario used in previous works represented by pedestrian crossing in urban environments under non-regulated conditions. A user study was then performed to investigate the various dimensions of vehicle-to-pedestrian interaction in both objective and subjective terms. Results showed that, although an interface clearly standing out over all the considered dimensions does not exists, one of the studied AR designs was able to provide state-of-the-art results in terms of safety and trust, at the cost of a higher cognitive effort and lower intuitiveness compared to LED panels showing anthropomorphic features. Together with rankings on the various dimensions, indications about advantages and drawbacks of the various alternatives that emerged from the study could be an important information source for next developments in the field

An operational research-based integrated approach for mass evacuation planning of a city

Large-scale disasters are constantly occurring around the world, and in many cases evacuation of regions of city is needed. ‘Operational Research/Management Science’ (OR/MS) has been widely used in emergency planning for over five decades. Warning dissemination, evacuee transportation and shelter management are three ‘Evacuation Support Functions’ (ESF) generic to many hazards. This thesis has adopted a case study approach to illustrate the importance of integrated approach of evacuation planning and particularly the role of OR/MS models. In the warning dissemination phase, uncertainty in the household’s behaviour as ‘warning informants’ has been investigated along with uncertainties in the warning system. An agentbased model (ABM) was developed for ESF-1 with households as agents and ‘warning informants’ behaviour as the agent behaviour. The model was used to study warning dissemination effectiveness under various conditions of the official channel. In the transportation phase, uncertainties in the household’s behaviour such as departure time (a function of ESF-1), means of transport and destination have been. Households could evacuate as pedestrians, using car or evacuation buses. An ABM was developed to study the evacuation performance (measured in evacuation travel time). In this thesis, a holistic approach for planning the public evacuation shelters called ‘Shelter Information Management System’ (SIMS) has been developed. A generic allocation framework of was developed to available shelter capacity to the shelter demand by considering the evacuation travel time. This was formulated using integer programming. In the sheltering phase, the uncertainty in household shelter choices (either nearest/allocated/convenient) has been studied for its impact on allocation policies using sensitivity analyses. Using analyses from the models and detailed examination of household states from ‘warning to safety’, it was found that the three ESFs though sequential in time, however have lot of interdependencies from the perspective of evacuation planning. This thesis has illustrated an OR/MS based integrated approach including and beyond single ESF preparedness. The developed approach will help in understanding the inter-linkages of the three evacuation phases and preparing a multi-agency-based evacuation planning evacuatio