Human Road Users Research Articles

Pedestrian's risk-based negotiation model for self-driving vehicles to get the right of way

Negotiations among drivers and pedestrians are common on roads, but it is still challenging for a self-driving vehicle to negotiate for its right of way with other human road users, especially pedestrians. Currently, the self-driving vehicles are programmed for conservative behavior, yielding to approaching pedestrians. Consequently, the future urban traffic will slow down significantly. In this paper, a conceptual model of vehicle–pedestrian negotiation is proposed. This model allows individual decision making of multiple vehicles and pedestrians, extending a prior negotiation model for a single vehicle and a single pedestrian. The possible negotiation opportunities for vehicles are modeled considering different risk-taking behaviors of pedestrians. Simulation results show an overall improvement in the waiting time of vehicles and thus in the intersection throughput, compared to conservative vehicle behavior. The simulation results show also that the benefit of reduced waiting times for vehicles comes at the cost of some waiting time for pedestrians. However, the observed pedestrian waiting times in this model are not more than the generally accepted waiting times reported in empirical studies.

Safe System Speed Management

Speed management is crucial to a safe road and traffic system. Unsafe speeds travelled by motor vehicles contributes to around 40% of road fatalities. This lecture discusses the pivotal role of speed management in safe system road safety and how to address the problem of speeding. With the adoption of Safe System principles for road safety strategies, it is no longer acceptable that people should die or be seriously injured due to mistakes made when using roads. The design and management parameter for road and traffic systems should focus on the fallibility and vulnerability of human road users. Speed is a most critical factor because it is the crash impact speed that determines the degree of harm that is inflicted on people. Speed management is perhaps the most contested issue in road safety and the most difficult one to perform effectively. Part of this problem has to do with the very nature of human beings. Instead of making every effort to keep safe, people tend to always try to optimise the benefits of their risk behaviour. To make things worse, behavioural research has found that human beings do not generally judge risk accurately and have an optimism bias. So, when it comes to driving speed selection people tend to misjudge the time it will take for them to take evasive action or stop in time to avoid a crash. Perception, reaction and braking times will be covered in this lecture. From crash data analysis and biomechanical research findings the impact crash speeds that can kill people in various crash types are now known. For example, the percentage of risk of fatally injuring a pedestrian rises sharply after the impact speed exceeds 30 km/h. Road networks generally have a variety of functions. There are roads that have primarily flow through functions, roads with access functions and roads that serve to cater for a mix of vulnerable and less vulnerable road users. The Dutch first fostered the notion that road hierarchies should be defined, encompassing all of the functions that the road network aims to support. Then possible crash or traffic conflict types can be analysed. If the overriding priority is to prevent road deaths, the safe limit for roads with possible conflicts between cars and unprotected road users is 30 km/h or lower. For locations where impacts with fixed roadside objects are possible the limit should be no higher than 40km/h. For intersections with possible lateral conflicts between cars 50km/h would be the maximum limit. Roads with possible head-on crashes between cars would have a limit no greater than 70 km/h. Where head-on and side-on conflicts with other road users are impossible, limits greater than 70 km/h can be considered. Motorways with side barriers and centre barriers should be limited to 110 km/h maximum. This lecture will discuss the actions that can be taken to prevent speed-related road injuries and fatalities. It will cover social, behavioural and engineering solutions.

Designing for Interactions with Automated Vehicles: Ethnography at the Boundary of Quantitative‐Data‐Driven Disciplines

This case study presents ethnographic work in the midst of two fields of technological innovation: automated vehicles (AV) and virtual reality (VR). It showcases the work of three MSc. Techno‐Anthropology students and their collaboration with the EU H2020 project ‘interACT', sharing the goal to develop external human‐machine interfaces (e‐HMI) for AVs to cooperate with human road users in urban traffic in the future. The authors reflect on their collaboration with human factor researchers, data scientists, engineers, experimental researchers, VR‐developers and HMI‐designers, and on experienced challenges between the paradigms of qualitative and quantitative research. Despite the immense value of ethnography and other disciplines to collectively create holistic representations of reality, this case study reveals several tensions and struggles to align multi‐disciplinary worldviews. Results show the value of including ethnographers: 1) in the design and piloting of a digital observation app for the creation of large datasets; 2) in the analysis of large amounts of data; 3) in finding the potential of and designing e‐HMI concepts; 4) in the representation of real‐world context and complexity in VR; 5) in the evaluation of e‐HMI prototypes in VR; and finally 6) in critically reflecting on the construction of evidence from multiple disciplines, including ethnography itself.

Designing the interaction of automated vehicles with other traffic participants: design considerations based on human needs and expectations

Automated vehicles (AV) are expected to be integrated into mixed traffic environments in the near future. As human road users have established elaborated interaction strategies to coordinate their actions among each other, one challenge that human factors experts and vehicle designers are facing today is how to design AVs in a way that they can safely and intuitively interact with other traffic participants. This paper presents design considerations that are intended to support AV designers in reducing the complexity of the design space. The design considerations are based on a literature review of common human–human interaction strategies. Four categories of information are derived for the design considerations: (1) information about vehicle driving mode; (2) information about AVs’ manoeuvres; (3) information about AVs’ perceptions of the environment; and (4) information about AVs’ cooperation capabilities. In this paper, we apply the four categories to analyse existing research studies of traffic participants’ needs during interactions with AVs and results of the CityMobil2 project. From the CityMobil2 project we present central results from face-to-face interviews, an onsite-survey and two focus groups. To further support the AV designers we describe and rate different design options to present the information of the four categories, including the design of the infrastructure, the vehicle shape, the vehicle manoeuvres and the external human–machine interface of the AV.

“What Makes a Cooperative Driver?” Identifying parameters of implicit and explicit forms of communication in a lane change scenario

An automated vehicle needs to learn how human road users communicate with each other in order to avoid misunderstandings and prevent giving a negative outward image during interactions. The aim of the present work is to develop an autonomous driving system which communicates its intentions to change lanes based on implicit and explicit rules used by human drivers. To reach this goal, we aimed at gaining a deeper understanding of which aspects of lane change behaviour makes them cooperative from the perspective of other drivers. Therefore a vehicle used various lane change announcement strategies by varying combinations of driving parameters in a static driving simulator. (First study: Start indicator signal, Waittime, lane change duration; Second study: Longitudinal acceleration). It’s impact on the perception and behaviour of other road users was observed in two studies (N = 25 per study). The results showed that the earlier the merging vehicle was indicating its intentions, the more cooperative it was perceived. When turning on the indicator at a later time participants considered it as more cooperative to merge with a slower or faster lane change duration or to wait longer in the lane before starting to move to the other lane. An early longitudinal acceleration when starting to change lanes is perceived more cooperative. These findings can be used to model a lane change strategy based on human behaviour, which will eventually lead to more acceptable and safer interactions between automated and non-automated road users.

Cooperation behaviour of road users in t-intersections during deadlock situations

Mixed traffic between automatic guided cars and human road users makes it necessary to understand cooperative behaviour between road users in order to adapt automated behaviour to human expectations. Road traffic offers various challenges, one being cooperative situations, which are not regulated by law. For example a t-intersection in which one road user is driving straight forward and two road users are turning left. To solve this situation the road users have to cooperate with each other. Different kinds of approaching behaviours in such situations were generated and analyzed according to cooperation readiness, preference to drive first and perceived safety of the situation by means of an experiment.The results show that in complex situations – like the investigated scenario – human road users prefer not to drive first. Additionally a high cooperation readiness of the opposite driver combined with a defensive driving style received higher ratings in the “confidence of passing”.