Ching-Yao Chan

Pedestrian detection in transit bus application: sensing technologies and safety solutions

Pedestrian safety is a primary traffic issue in urban environment. The use of modern sensing technologies to improve pedestrian safety has remained an active research topic for years. A variety of sensing technologies have been developed for pedestrian detection. The application of pedestrian detection on transit vehicle platforms is desirable and feasible in the near future. In this paper, potential sensing technologies are first reviewed for their advantages and limitations. Several sensors are then chosen for further experimental testing and evaluation. A reliable sensing system will require a combination of multiple sensors to deal with near-range in stationary conditions and longer-range detection in moving conditions. An approach of vehicle-infrastructure integrated solution is suggested for the pedestrian detection in transit bus application.

Characterization of Driving Behaviors Based on Field Observation of Intersection Left-Turn Across-Path Scenarios

There have been significant research and developments in recent years for intersection-safety solutions that are intended to alert drivers of hazardous situations by utilizing sensing, computing, and communication technologies. Since the effectiveness of intersection-safety systems depends strongly on driver perception and acceptance of the provided warning signal, the understanding of driver actions under the targeted scenario is a central research topic. One significant safety concern at intersections is the left-turn crossing-path scenarios, where a left-turning vehicle is confronted by oncoming traffic. This paper describes the analysis and synthesis of real-world data for such scenarios observed in field observations. Specifically, traffic interactions in left-turn across-path situations are evaluated to compare data from various intersections with different operation and traffic attributes. The analyzed data were characterized to gain insight into a time gap acceptance exhibited by a population of drivers. The knowledge of driving behaviors can provide the guidelines for future investigation as well as a knowledge basis for the selection of warning criteria to allow timely alerts to drivers in the intended safety applications

On the detection of vehicular crashes-system characteristics and architecture

Safety systems for ground vehicles are deployed in different phases according to the timing of activation relative to the occurrence instant of an accident. Collision warning or avoidance systems function prior to an accident, while occupant protection systems act during a collision to mitigate the damage or injuries caused by an accident. This paper deals with crash sensing systems that detect a collision and evaluate the severity of a crash. One major application of these sensing systems is their current use in occupant restraint systems. They may also be utilized in the future for advanced vehicle control and safety systems. With air bags becoming standard equipment in new passenger vehicles, crash sensing technologies have advanced considerably. Yet, existing challenges and new innovations continue to demand improvements in their functions. This paper focuses on the system performance of crash sensing systems. The purpose of this paper is to propose a framework of addressing various design issues from both a component level and a system perspective. Through the discussions of crash data analysis, the design concepts of crash sensors are highlighted. The characteristics of representative mechanical and electronic sensors are analyzed and the guidelines of sensor selection to meet design requirements are discussed. Also, an assessment of sensor reliability is reviewed with various system architectures. Finally, suggestions are made to enhance system performance in areas that may benefit from the addition of sensing functionality. The public has become conscientiously aware of the importance of transportation safety. With more advanced technologies introduced into ground vehicles, the safety concerns will intensify. The demand for a friendly driving environment and vehicle interior will further promote the requirements of vehicular safety systems. Crash sensing will remain a challenging and active area for years to come.

Evaluation of cooperative roadside and vehicle-based data collection for assessing intersection conflicts

Intersection collisions represent a significant portion of highway accidents. Recent research and development activities have suggested potential solutions to address this critical safety issue by supplying timely alerts to drivers of imminent collisions. These intersection decision support systems utilized sensor, communication and computer technologies to help drivers recognize risky conditions, thus actions can be taken to avoid collisions. A cooperative vehicle-infrastructure concept, built upon such premises, seek to combine the information available from vehicles and roadside in a synergistic framework so that a flexible yet sensible system can be deployed in the near future. The work presented in this paper represents an experimental effort conducted at a real-world intersection, by the use of an instrumented vehicle and roadside traffic monitoring, to explore technical challenges encountered in a vehicle-infrastructure integration approach.

Magnetic sensing as a position reference system for ground vehicle control

In advanced vehicle control and safety systems, position measurement is an important link for the identification of vehicle locations, such as lateral position relative to a lane or a desired trajectory. This paper focuses on magnetic sensing systems that are used for ground vehicle control and guidance. The magnetic fields from sample magnets are first measured to determine the characteristics of their patterns as the basis for detection and position identification. The effects of external objects, such as rebar or scraped metals on roadways, are then assessed with a random selection of potential objects. Tests are also conducted in a variety of infrastructure locations to observe the probable impacts from the earth fields on the recognition of magnet field patterns. Also presented in the paper is a discussion of sensing algorithms applicable to the sensing of magnets and their use for vehicle guidance. Exemplary measurements are shown to illustrate sensing approaches that have been considered or developed in real-time applications. Implications from different sensing algorithms regarding sensitivity to measurement variations are also reviewed. A list of design objectives and constraints for components of a magnetic sensing system is outlined as the basis for its optimization. With successful demonstrations in several applications and different operating environments, position measurements using magnetic markers have proven to be an appropriate candidate for ground vehicle guidance and control. For system-wide deployment of similar technologies, the subject deserves further investigations into broader issues such as system durability and total costs in conjunction with continual improvements in accuracy and reliability of sensing capabilities.

Observations of Driver Time Gap Acceptance at Intersections in Left-Turn Across-Path-Opposite-Direction Scenarios

Intersection collision warning systems can potentially reduce the number of collisions and associated losses. A critical design aspect of these systems is the selection of warning criteria, which represent a set of conditions and parameters under which the decision and the timing to issue warnings are determined. Proper warning criteria allow the generation of timely signals for drivers while minimizing false and nuisance alarms. The paper describes the development of a methodology to observe and analyze the selection of time gaps exhibited by driver behaviors in a real-world setting. The data collection procedures and analysis techniques are explained for left-turn across-path-opposite-direction scenarios, which constitute more than a quarter of crossing path crashes at intersections. Exemplar data sets from an urban, signalized intersection are used to illustrate methods of deriving time gap acceptance behaviors. The extracted information can serve as the basis for selecting gap acceptance thresholds in warning criteria, and the demonstrated methodology can be applied in the development of intersection collision warning systems.

Feasibility analysis of steering control as a driver-assistance function in collision situations

This paper addresses the feasibility of post-impact maneuvers that aim to mitigate accident sequences. In particular, the discussions emphasize the possibility of applying steering control to stabilize the trajectories of vehicles involved in a collision. The problem of interest is defined with descriptions of accident scenarios, limitations of applicability, and performance requirements. A model of vehicle dynamics is constructed to facilitate the design of steering controllers. Various collision scenarios are simulated to demonstrate the effectiveness of a generic feedback controller. The analysis provided herein shows steering control is promising as a driver-assistance function in emergency situations.

Trends in Crash Detection and Occupant Restraint Technology

In the past two decades, occupant restraint systems for automobiles have made considerable progress globally. There has been a tremendous increase in the complexity and sophistication of functional requirements. Particularly significant in the overall evolution of restraint systems is the growth in electronics content, which is concurrent with similar phenomena in the automotive world, as well as in many other technology-related fields. In conjunction with this trend, the shift to digital components and subsystems expanded, while the design of restraint systems has become more diversified with enhanced adaptability and flexibility. In addition to the airbags that are standardized for passenger vehicles, there has been a whole spectrum of emerging safety features that provide additional safety improvements. For example, rollover and occupant sensing are being added onto an integrated occupant protection system. Global positioning systems are coupled with crash sensors into emergency notification services. Increasingly, vehicles are now being equipped with active safety systems. The availability of both passive restraints and active safety functions will allow an additional layer of synergistic integration across safety systems. Research and developments in vehicular safety can be expected to remain active in the foreseeable future. This paper describes the system-level design trends that have occurred in the past and offers a perspective of future design transition in automotive restraint systems

Defining Safety Performance Measures of Driver-Assistance Systems for Intersection Left-Turn Conflicts

Vehicular safety research and development activities have been active in recent years with the implementation of driver assistance systems. Intersection collision is a primary category of roadway safety concerns that can benefit from vehicle-based as well as infrastructure-based solutions. This paper describes the definition of safety performance measures for the purpose of assessing the effectiveness of driver-assistance systems for intersection left-turn conflicts. The safety measures allow a comparison of performances in the design and development stages as well as the evaluation in the field testing and deployment stages. The availability of surrogate measures in the absence of the ultimate measures of crash reductions provides a realistic indication of plausible effects from safety improvements. The methodology of calculating the suggested safety measures is based on field observation data, thus lending strong support to the validity and applicability of the suggested approach

Safety Performance of High-Occupancy Vehicle (HOV) Facilities: Evaluation of HOV Lane Configurations in California

Collision data from High Occupancy Vehicle (HOV) facilities with two different types of access, continuous and limited, are examined in this paper. The findings show that HOV facilities with limited access offer no safety advantages over those with a continuous access. Compared with continuous access HOV lanes, a higher percentage of collisions was concentrated on limited access HOV lanes. Limited access HOV lanes also had higher collision rates. Findings from investigating the relationship between collision rates in HOV lanes with respect to shoulder width, length of access, and the proximity of access to its neighboring ramps are also documented. These findings provide enhanced understanding about the effects of geometric factors on the collision rates in HOV lanes.