Johan Engström

Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk

This work was sponsored by the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies. This project was managed by Ken Campbell, Chief Program Officer for SHRP 2 Safety , and Jim Hedlund, SHRP 2 Safety Coordinator . The research reported on herein was performed by the main contractor SAFER Vehicle and Traffic Safety Centre at Chalmers, Gothenburg, Sweden. SAFER is a joint research unit where 25 partners from the Swedish automotive industry, academia and authorities cooperate to make a center of excellence within the field of vehicle and traffic safety (see www.chalmers.se/safer ). The host and legal entity SAFER is Chalmers University of Technology. Principle Investigator Tr ent Victor is Adjunct Professor at Chalmers and worked on the project as borrowed personnel to Chalmers but his main employer is Volvo Cars. The other authors of this report are Co - PI Marco Dozza, Jonas Bargman, and Christian - Nils Boda of Chalmers Universi ty of Technology (as a SAFER partner) ; Johan Engstrom and Gustav Markkula of Volvo Group Trucks Technology (as a SAFER partner) ; John D. Lee of University of Wisconsin - Madison (as a consultant to SAFER); and Carol Flannagan of University of Michigan Transp ortation Research Institute (UMTRI) (as a consultant to SAFER). The authors acknowledge the contributions to this research from Ines Heinig, Vera Lisovskaja, Olle Nerman, Holger Rootzen, Dmitrii Zholud, Helena Gellerman , Leyla Vujic, Martin Rensfeldt, Stefan Venbrant, Akhil Krishnan, Bharat Mohan Redrouthu, Daniel Nilsson of Chalmers; Mikael Ljung - Aust of Volvo Cars; Erwin Boer; Christer Ahlstrom and Omar Bagdadi of VTI.

A Review of Research on Driving Styles and Road Safety

Objective: The aim of this study was to outline a conceptual framework for understanding driving style and, on this basis, review the state-of-the-art research on driving styles in relation to road safety. Background: Previous research has indicated a relationship between the driving styles adopted by drivers and their crash involvement. However, a comprehensive literature review of driving style research is lacking. Method: A systematic literature search was conducted, including empirical, theoretical, and methodological research, on driving styles related to road safety. Results: A conceptual framework was proposed whereby driving styles are viewed in terms of driving habits established as a result of individual dispositions as well as social norms and cultural values. Moreover, a general scheme for categorizing and operationalizing driving styles was suggested. On this basis, existing literature on driving styles and indicators was reviewed. Links between driving styles and road safety were identified and individual and sociocultural factors influencing driving style were reviewed. Conclusion: Existing studies have addressed a wide variety of driving styles, and there is an acute need for a unifying conceptual framework in order to synthesize these results and make useful generalizations. There is a considerable potential for increasing road safety by means of behavior modification. Naturalistic driving observations represent particularly promising approaches to future research on driving styles. Application: Knowledge about driving styles can be applied in programs for modifying driver behavior and in the context of usage-based insurance. It may also be used as a means for driver identification and for the development of driver assistance systems.

Effects of Working Memory Load and Repeated Scenario Exposure on Emergency Braking Performance

Objective: The objective of the present study was to examine the effect of working memory load on drivers’ responses to a suddenly braking lead vehicle and whether this effect (if any) is moderated by repeated scenario exposure. Background: Several experimental studies have found delayed braking responses to lead vehicle braking events during concurrent performance of nonvisual, working memory—loading tasks, such as hands-free phone conversation. However, the common use of repeated, and hence somewhat expected, braking events may undermine the generalizability of these results to naturalistic, unexpected, emergency braking scenarios. Method: A critical lead vehicle braking scenario was implemented in a fixed-based simulator. The effects of working memory load and repeated scenario exposure on braking performance were examined. Results: Brake response time was decomposed into accelerator pedal release time and accelerator-to-brake pedal movement time. Accelerator pedal release times were strongly reduced with repeated scenario exposure and were delayed by working memory load with a small but significant amount (178 ms). The two factors did not interact. There were no effects on accelerator-to-brake pedal movement time. Conclusion:The results suggest that effects of working memory load on response performance obtained from repeated critical lead vehicle braking scenarios may be validly generalized to real world unexpected events. Application: The results have important implications for the interpretation of braking performance in experimental settings, in particular in the context of safety-related evaluation of in-vehicle information and communication technologies.

A General Conceptual Framework for Modelling Behavioural Effects of Driver Support Functions

In recent years, the number of in-vehicle functions interacting with the driver has increased rapidly. This includes both driving support functions (e.g. anti-lock brakes, collision warning systems, adaptive cruise control) and functions supporting non-driving tasks, e.g. communication and entertainment functions. Today, many of these functions are also featured on portable computing systems, commonly referred to as nomadic devices. Moreover, in order to handle this growth in diversity and complexity of in-vehicle functionality, several types of meta functions for human-machine interface integration and adaptation have been proposed. Such functions, often referred to as workload management functions, are intended to resolve potential conflicts between individual functions with respect to their interaction with the driver (see Engstrom et al., 2004; Brostrom et al., 2006). The term driver support functions will henceforth be used to refer to in-vehicle functions that support what drivers do, whether related to driving or not.

Demonstration of Two-Dimensional Temperature Characterization of Valves and Transparent Piston in a GDI Optical Engine

Thermographic phosphors thermometry was used to measure engine valves and transparent piston temperatures in two dimensions as well point wise of a running, optically accessible, gasoline direct injection engine. The engine, fueled with isooctane, was operated in continuous and skip-fire mode at 1200 and 2000 rpm. A calibration of the phosphorescence lifetime and spectral properties against temperature allowed temperature measurements between 25 and 600mDC. Results from the measurements show the potential of the technique for two-dimensional mapping of engine walls, valves and piston temperatures inside the cylinder.

Piston Temperature Measurement by Use of Thermographic Phosphors and Thermocouples in a Heavy-Duty Diesel Engine Run Under Partly Premixed Conditions

Piston temperature experiments were conducted in a single-cylinder heavy-duty diesel research engine both by use of optical temperature sensitive phosphor and of thermocouples mounted on the piston surface. In the former case, a thin coating of a suitable thermographic phosphor was applied to the areas on the piston surface to be investigated. The optical measurements involved the use of an optical window and of an endoscope. The possibility of using optical fibres into guide light in and out of the engine was also investigated. Results of the optical and of the thermocouple measurements were compared and were also related to more global data with the aim of exploring the use of thermographic phosphors for piston-temperature measurements in diesel engine. Thermographic phosphors thermometry was found to represent an alternative to the thermocouple method since it easily can be applied to various piston geometries.

A conceptual framework for requirement specification and evaluation of active safety functions

Active safety functions intended to prevent vehicle crashes are becoming increasingly prominent in traffic safety. Successful evaluation of their effects needs to be based on a conceptual framework, i.e. agreed-upon concepts and principles for defining evaluation scenarios, performance metrics and pass/fail criteria. The aim of this paper is to suggest some initial ideas toward such a conceptual framework for active safety function evaluation, based on a central concept termed ‘situational control’. Situational control represents the degree of control jointly exerted by a driver and a vehicle over the development of specific traffic situations. The proposed framework is intended to be applicable to the whole evaluation process, from ‘translation’ of accident data into evaluation scenarios and definition of evaluation hypotheses, to selection of performance metrics and criteria. It is also meant to be generic, i.e. applicable to driving simulator and test track experiments as well as field operational tests.

Visualization of Egr Influence on Diesel Combustion With Long Ignition Delay in a Heavy-Duty Engine

The effects of EGR on diesel combustion were visually examined in a single-cylinder, heavy-duty research engine with a low compression ratio, low swirl, a CR fuel injection system and an eight-orifice nozzle. Optical access was primarily obtained through the cylinder head. The effects of EGR were found to be significant. NOx emissions were reduced from over 500 ppm at 0% EGR to 5 ppm at 55% EGR. At higher levels of EGR (approximately 35% or more) there was a loss in efficiency. Constant fuel masses were injected. Results from the optical measurements and global emission data were compared in order to obtain a better understanding of the spray behavior and mixing process. Optical measurements provide fundamental insights by visualizing air motion and combustion behavior. The NOx reductions observed might be explained by reductions in oxygen concentration associated with the increases in EGR.

Effects of Cognitive Load on Driving Performance: The Cognitive Control Hypothesis

Objective: The objective of this paper was to outline an explanatory framework for understanding effects of cognitive load on driving performance and to review the existing experimental literature in the light of this framework. Background: Although there is general consensus that taking the eyes off the forward roadway significantly impairs most aspects of driving, the effects of primarily cognitively loading tasks on driving performance are not well understood. Method: Based on existing models of driver attention, an explanatory framework was outlined. This framework can be summarized in terms of the cognitive control hypothesis: Cognitive load selectively impairs driving subtasks that rely on cognitive control but leaves automatic performance unaffected. An extensive literature review was conducted wherein existing results were reinterpreted based on the proposed framework. Results: It was demonstrated that the general pattern of experimental results reported in the literature aligns well with the cognitive control hypothesis and that several apparent discrepancies between studies can be reconciled based on the proposed framework. More specifically, performance on nonpracticed or inherently variable tasks, relying on cognitive control, is consistently impaired by cognitive load, whereas the performance on automatized (well-practiced and consistently mapped) tasks is unaffected and sometimes even improved. Conclusion: Effects of cognitive load on driving are strongly selective and task dependent. Application: The present results have important implications for the generalization of results obtained from experimental studies to real-world driving. The proposed framework can also serve to guide future research on the potential causal role of cognitive load in real-world crashes.

Towards the Automotive HMI of the Future: Mid-Term Results of the AIDE Project

AIDE is an integrated project funded by the EC in the 6th Framework Programme. The project, which involves 30 partners including all major European vehicle manufacturers, deals with behavioural and technical issues related to automotive human-machine interface (HMI) design, with a particular focus on HMI integration and adaptation. The project involves tightly integrated empirical research, driver behaviour modelling and methodological- as well technological development. This paper provides an overview of the mid-term results achieved about half-way through the four-year project.