Analyzing and Modeling Drivers’ Deceleration Behavior from Normal Driving

Abstract

Most research in vehicle automation has mainly focused on the safety aspect with only limited studies on occupants' discomfort. In order to facilitate their rapid uptake and penetration, autonomous vehicles (AVs) should ensure that occupants are both safe and comfortable. Recent research however revealed that people felt uncomfortable when AVs braked. This may be due to their robot-like braking performance. Existing studies on drivers' braking behaviour investigated data either from controlled experiments or driving simulators. There is a dearth of research on braking behaviour in normal driving. The objective of this paper is therefore to examine drivers' braking behaviours by exploiting naturalistic driving data from the Pan-European TeleFOT (Field Operational Tests of Aftermarket and Nomadic Devices in Vehicles) project. On a fixed route of 16.5km long, 16 drivers were asked to drive an instrumented vehicle. A total of about eleven million observations were analysed to identify the profile, value and duration of deceleration events. Since deceleration events are nested within trips and trips within drivers, multilevel mixed-effects linear models were employed to develop relationships between deceleration value and duration and the factors influencing them. The results indicate that the most used profile of the deceleration behaviour follows a hard braking at the beginning when detecting a danger and then becomes smoother. Furthermore, they suggest that the speed, the reason for braking and the deceleration profile mostly affect the deceleration events. Findings from this study should be considered in examining the braking behaviour of AVs.Deligianni, Quddus, Morris, Anvuur, Reed 3 INTRODUCTIONResearch on autonomous vehicles (AVs) has attracted a significant interest from the research community worldwide in recent years. Fundamentally, vehicle automation aims to eliminate or decrease human involvements from the routine tasks of driving (1). Ensuring human-like driving performance is however a basic condition for the wide acceptance of (semi)autonomous vehicles (2).Despite the remarkable research and development progress in the area of (semi)autonomous vehicles over the last decade, there is a concern that occupants may not feel comfortable due to the unnatural driving performance of the current technology which sometimes differs from the average human driving (2). Driver comfort is understood as a state which is achieved by the removal or absence of uneasiness and distress. Even though many factors may affect driver's comfort (such as lateral and longitudinal acceleration, time headway etc.), one of the most important is the braking. In other words, a (semi)autonomous vehicle should decelerate in the style which could avoid mental discomfort to the people both inside and outside of the vehicle. Regarding the braking performance, stress and nervousness are apparent if the timing at which the vehicle automatically brakes differs from the driver's own judgment or whether the level of deceleration is great...

Communicating the intention of an automated vehicle to pedestrians: The contributions of eHMI and vehicle behavior

“…In the yielding conditions, it came to a full stop at 5 m before the pedestrian. The three different yielding behaviors exhibited different braking characteristics: Gentle braking: At a distance of 45 m away from the pedestrian, the car started to brake steadily, to indicate a deliberate but smooth yielding behavior, resulting in a total braking distance of 40 m. This was done to emulate a deceleration rate of 2.4 m/s 2 which was found as the deceleration rate for average and common braking by previous research [5]. This condition was therefore treated as a representative of a 'normal' braking pattern which would ideally correspond with a 'yielding' message from an eHMI.…”

“…Aggressive braking: At a distance of 24 m away from the pedestrian, the car braked hard. In this aggressive yielding behavior, the total braking distance was 19 m. This was done to emulate a deceleration rate of 5.17 m/s 2 which was found as the maximum deceleration rate for hard braking by previous research [5]. This condition was therefore treated as a representative of behavior that would initially seem to contradict a 'yielding' message from an eHMI.…”

Examining lane change gap acceptance, duration and impact using naturalistic driving data

“…On the other hand, there might be variation between lead gaps from different lane change motivations and/or different road types, i.e., between-cluster variation. Therefore, a statistical model is needed to jointly control both within-and betweencluster variations(Deligianni et al, 2017).…”

Stress-inducing factors among occupational drivers in Karachi, Pakistan

“…Additionally, a study project conducted among Pan-Europeans found that behaviour of drivers, specifically deceleration, was mainly due to detecting danger on the road followed by hard braking that resulted in slowing of the vehicle (31). Thus, anxiety and stress play a major role defining the behaviour of drivers while driving.…”