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Technical Paper

Heavy Truck Crash Analysis and Countermeasures to Improve Occupant Safety

This paper examines truck driver injury and loss of life in truck crashes related to cab crashworthiness. The paper provides analysis of truck driver fatality and injury in crashes to provide a better understanding of how injury occurs and industry initiatives focused on reducing the number of truck occupant fatalities and the severity of injuries. The commercial vehicle focus is on truck-tractors and single unit trucks in the Class 7 and 8 weight range. The analysis used UMTRI's Trucks Involved in Fatal Accidents (TIFA) survey file and NHTSA's General Estimates System (GES) file for categorical analysis and the Large Truck Crash Causation Study (LTCCS) for a supplemental clinical review of cab performance in frontal and rollover crash types. The paper includes analysis of crashes producing truck driver fatalities or injuries, a review of regulatory development and industry safety initiatives including barriers to implementation.
Technical Paper

Effectiveness of a Current Commercial Vehicle Forward Collision Avoidance and Mitigation Systems

This paper focuses on the safety performance of Commercial Vehicle Forward Collision Avoidance and Mitigation Systems (F-CAM) that include Forward Collision Warning (FCW) with Collision Mitigation Braking (CMB) technology as applied to heavy trucks, including single unit and tractor semitrailers. The study estimated the safety benefits of a commercially available F-CAM system considered to be representative of products currently in service. The functional characteristics were evaluated and its performance generically modeled to estimate safety benefits. This was accomplished through the following steps: (1) first characterize the actual performance of these systems in various pre-crash scenarios under controlled test track conditions, and then reverse engineering the algorithms that control warnings and automatic braking actions; (2) developing a comprehensive set of simulated crash events representative of actual truck striking rear-end crashes.
Technical Paper

Automated Control and Brake Strategies for Future Crash Avoidance Systems - Potential Benefits

This paper explores the potential safety performance of “Future Generation” automated speed control crash avoidance systems for Commercial Vehicles. The technologies discussed in this paper include Adaptive Cruise Control (ACC), second and third generation Forward Collision Avoidance and Mitigation Systems (F-CAM) comprised of Forward Collision Warning (FCW) with Collision Mitigation Braking (CMB) technology as applied to heavy trucks, including single unit and tractor semitrailers. The research [1[ discussed in this paper is from a study conducted by UMTRI which estimated the safety benefits of current and future F-CAM systems and the comparative efficacy of adaptive cruise control. The future generation systems which are the focus of this paper were evaluated at two separate levels of product refinement, “second generation” and “third generation” systems.
Technical Paper

Real-World Safety Effect of Roll Stability Control

Heavy truck rollover remains a primary factor in truck driver fatalities and injury. Roll stability control (RSC) and electronic stability control (ESC) are technologies that have been introduced to reduce the incidence of rollover in heavy truck crashes. This report provides an analysis of the real-world experience of a large for-hire company that introduced RSC into its fleet starting in 2004. The carrier provided a well-documented set of data on the operations of its truck-tractors, including both those equipped with RSC and those that did not have RSC installed. The purpose of the analysis is to determine the effect of RSC on the probability of rollover, as well as to identify other factors that either contribute to rollover or help reduce its incidence. This study presents results on the incidence of rollover both in terms of rollovers per 100 million miles traveled and the percentage of crashes that resulted in rollover.
Technical Paper

Regulatory Options for Improving Aerodynamic Performance of Commercial Vehicles

This paper examines how commercial vehicle aerodynamic improvements can be influenced by regulation particularly with respect to size and weight policy. It discusses the potential use of performance based standards (PBS) first introduced to optimize vehicle configurations in terms of vehicle stability and control and compatibility with highway geometry. There are several vehicle treatments that can be used to reduce aerodynamic drag, some of which lengthen or widen the vehicle without increasing cargo capacity. One such solution is referred to as ‘boat tails” consisting of a light weight external extension of the trailer allowing the air flow to remain attached as the vehicle cross section diminishes resulting in a reduction in the area of negative pressure at the end of the vehicle which reduces drag force.
Journal Article

Safety Performance and Benefits of Heavy Truck Stability Control: Providing Insight into Compliance Evaluation

This paper contains an analysis of the potential safety benefits of electronic stability control (ESC) for single unit trucks and tractor semitrailers within the U.S. operating environment. It is based on research projects [1,2] which combined hardware-in-the-loop simulation and vehicle testing with the analysis of independent crash datasets using engineering and statistical techniques to estimate the probable safety benefits of stability control technologies for 5-axle tractor-semitrailer vehicles and single unit trucks. The characteristics of ESC-relevant crashes involving these two vehicle classes were found to be very different as were the control strategies needed for crash avoidance. Rollover was the dominant ESC relevant crash type for tractor semitrailers while loss of control was the dominant ESC relevant crash for straight trucks.
Technical Paper

Characterization of Commercial Vehicle Crashes and Driver Injury

About 360,000 commercial trucks are involved in traffic accidents in the United States per year. Approximately 20,000 truck drivers are injured in those crashes. This study examines traffic crashes of the commercial truck fleet for model years 2000 to 2008 contained in the Trucks Involved in Fatal Accidents (TIFA) and General Estimates System (GES) databases. Specifically, driver injuries, using the KABCO scale (injury severity), were analyzed to determine the association with crash type as well as with the truck configuration. A crash typology was developed to identify crash types, including the type of other vehicle or object struck as well as the impact point on the truck, associated with the most serious injuries. This research focuses on the frequency of commercial vehicle accidents and driver injury levels rather than the cause of the vehicle crash. Based on these findings, example cases from LTCCS were selected. These examples typify the most frequent crashes and injuries.
Technical Paper

The Correlation of Heavy Vehicle Performance Measures

Performance measures such as static roll stability, rearward amplification and load transfer ratio are a means to assess the engineering performance of heavy vehicles and to support truck size and weight policy decisions. It was expected that, for a particular vehicle configuration, there would be some degree of correlation between the various performance attributes. For example, a relatively high static roll stability may be associated with a relatively low load transfer ratio, at least within a particular vehicle configuration. In terms of developing performance measures such correlations are of great significance because (i) the number of performance attributes requiring specification may be reduced and (ii) potential conflicts between performance criteria in different attributes may be avoided. This type of analysis has not been carried out before, and requires a large database of performance numerics in order to determine relationships between each of the performance attributes.
Technical Paper

Heavy Truck Suspension Dynamics: Methods for Evaluating Suspension Road Friendliness and Ride Quality

Evaluating heavy truck suspensions for road friendliness and ride quality is a complex challenge An experimental study has been conduced to explore various options for evaluating suspension performance The methods examined use laboratory equipment and focus on evaluating suspension performance without the influence of the whole vehicle The experimental program found that “in phase sinusoidal frequency sweep” of constant amplitude produced clear differentiation of suspension response
Technical Paper

Heavy Truck Suspension Damper Performance for Improved Road Friendliness and Ride Quality

The use of dampers (shock absorbers) in heavy truck suspensions is central to reducing dynamic wheel loads. Dynamic wheel loads are responsible for a significant component of vehicle related road damage. Improving the viscous damping characteristics of suspensions will substantially reduce dynamic wheel loads thereby enhancing suspension “road-friendliness”. Because dampers deteriorate over time, a new test is required to determine the in-service condition of dampers. There is a need to develop improved dampers that are optimized to reduce dynamic wheel loads while providing good ride quality. They must be sufficiently robust to dissipate the required energy from various magnitudes of road unevenness over extended life cycles.