A human factors approach to defining requirements for low-speed autonomous vehicles to enable intelligent platooning

This paper presents results from a series of focus groups, aimed at enhancing technical engineering system requirements, for a public transport system, encompassing a fleet of platooning low-speed autonomous vehicles (LSAV; aka pods) in urban areas. A critical review of the pods was conducted, as part of a series of technical workshops, to examine the key areas of the system that could affect users and other stakeholders, such as businesses and the public. These initial findings were used to inform a series of focus groups, aimed at identifying the public's views of multiple autonomous vehicles being deployed in a pedestrianised area that can join and form platoons. Analysis of findings from the focus groups suggests that while people view platooning public transport vehicles favourably as a passenger, they have some concerns from a pedestrian perspective. Thematic analysis was applied to these findings and a systematic approach was used to identify where subjective outputs could be formalised to inform requirements. Finally, a step-by-step requirements elicitation process is presented that illustrates the method used to convert qualitative user data to objective engineering requirements

An evolutionary approach to the optimisation of autonomous pod distribution for application in an urban transportation service

For autonomous vehicles (AVs), which when deployed in urban areas are called “pods”, to be used as part of a commercially viable low-cost urban transport system, they will need to operate efficiently. Among ways to achieve efficiency, is to minimise time vehicles are not serving users. To reduce the amount of wasted time, this paper presents a novel approach for distribution of AVs within an urban environment. Our approach uses evolutionary computation, in the form of a genetic algorithm (GA), which is applied to a simulation of an intelligent transportation service, operating in the city of Coventry, UK. The goal of the GA is to optimise distribution of pods, to reduce the amount of user waiting time. To test the algorithm, real-world transport data was obtained for Coventry, which in turn was processed to generate user demand patterns. Results from the study showed a 30% increase in the number of successful journeys completed in a 24 hours, compared to a random distribution. The implications of these findings could yield significant benefits for fleet management companies. These include increases in profits per day, a decrease in capital cost, and better energy efficiency. The algorithm could also be adapted to any service offering pick up and drop of points, including package delivery and transportation of goods

Exploring the impact of autonomous taxis on people with disabilities

Over the past two decades, transportation has become more accessible, but people with disabilities still face significant barriers to accessing these services. This research focuses on the impact of autonomous taxis on people with disabilities, an area that has seen limited improvement. The study aims to answer two research questions: 1) How do traditional taxi experiences shape expectations of autonomous taxis in terms of disability accessibility? 2) To what extent does the autonomy of self-driving taxis contribute to a perceived increase in travel freedom? Thirty-two semi-structured interviews were conducted with administrative staff from disability organizations, and the perspectives of 39,079 organization members were included. Thematic and sentiment analyses were applied to analyse the findings, which revealed three main themes: onboarding, in-vehicle conditions, and offboarding. The absence of a driver was strongly correlated with a positive sentiment of increased travel freedom, indicating that autonomous taxis could provide enhanced accessibility without the limitations or biases associated with traditional taxis. Participants expressed concerns about driver attitudes and behaviour as negative experiences with traditional taxis. In contrast, with autonomous taxis, their main concern was the availability of human assistance to meet specific user needs throughout the journey. This study emphasizes the necessity for further research into the diverse and intricate spectrum of disabilities, as well as the importance of user-centric market research in the design process. Such research is crucial in achieving the overarching goal of improved accessibility

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

The relationship between aggressive driving and driver performance : a systematic review with meta-analysis

Traffic crashes remain a leading cause of accidental human death where aggressive driving is a significant contributing factor. To review the driver’s performance presented in aggressive driving, this systematic review screens 2412 pieces of relevant literature, selects and synthesizes 31 reports with 34 primary studies that investigated the driver’s control performance among the general driver population in four-wheeled passenger vehicles and published with full text in English. These 34 selected studies involved 1731 participants in total. By examining the selected 34 studies, the measures relating to vehicle speed (e.g., mean speed, n = 22), lateral control (e.g., lane deviation, n = 17) and driving errors (e.g., violation of traffic rules, n = 12) were reported most frequently with a significant difference observed between aggressive driving and driving in the control group. The result of the meta-analysis indicates that the aggressive driving behaviour would have 1) a significantly faster speed than the behaviour in the control group with an increase of 5.32 km/h (95% confidence interval, [3.27, 7.37] km/h) based on 8 studies with 639 participants in total; 2) 2.51 times more driving errors (95% confidence interval, [1.32, 3.71] times) than the behaviour in the control group, based on 5 studies with 136 participants in total. This finding can be used to support the identification and quantification of aggressive driving behaviour, which could form the basis of an in-vehicle aggressive driving monitoring system

Performance analysis of mmWave vehicle-to-vehicle communications : a stochastic geometry approach

Advanced sensory systems are the driving force behind autonomous vehicles. They have led to such vehicles producing and processing much more content-intensive visual data. It is foreseen that traffic consisting solely of autonomous vehicles will enable people and goods to travel more safely. Using millimetre wave (mmWave) frequencies for wireless communication between vehicles is a rising research topic, both to enhance safety and reliability of autonomous vehicles and to meet the data rate required by the content-intensive data-set produced by their advanced sensory systems. The main goal of this thesis is to make a stochastic analysis of the signal quality that can be achieved by vehicles when using mmWave frequencies for the wireless communication between them. To address this issue, the tools of stochastic geometry is used in this thesis. Firstly, stochastic geometry provides advanced mathematical properties to model the system fairly accurate and tractable. Secondly, resulting analytical model helps system designers to develop insights to understand relationships between system parameters. The first academic contribution of this thesis is a two-fold probabilistic connectivity analysis of an autonomous vehicle fleet for a single-lane road. In other words, it stochastically models the connectivity probability of the sensory data of the head and tail vehicles of the fleet shared over intermediate fleet vehicles by using a Poisson point process and geometric probability tools. The proposed model takes into account both the threshold of the obtained Signal-to-interference-plus-noise ratio in terms of the critical distance requirements and the beam misalignment issues caused by the lateral displacement of the vehicles in the lane. The second contribution of this thesis is a mean interference analysis for a typical receiver if the vehicles employ in-lane and closest vehicle routing schemes for a two-lane road. By comparing these two routing schemes, a strategy is proposed for different antenna beam widths and vehicle densities. Additionally, the distribution of autonomous vehicular traffic, that is modelled by the shifted Poisson point process, gains more realism by taking into account platooning-based headway distance requirements. The third contribution of this thesis is a derivation of the coverage probability and road spectral efficiency for multi-lane vehicle-to-vehicle communications, by taking into account the blockage impact of adjacent lane vehicles and antenna-placement dependent path loss behaviour under an in-lane routing scheme. Finally, all the analytical models are verified by Monte Carlo simulations