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Technical Paper

The Effect of Target Features on Toyota’s Autonomous Emergency Braking System

The Pre-Collision System (PCS) in Toyota’s Safety Sense package includes an autonomous emergency braking feature that can stop or slow a vehicle independent of driver input if there is an impending collision. The goals of this study were to determine how hazard characteristics, specifically radar reflector size and degree of target edge contrast, affect the response of the PCS, as well as to scrutinize tests wherein the PCS failed to stop the vehicle before impact. We conducted 80 tests with a 2017 Toyota Corolla driven towards a car-like target in a straight line and under constant accelerator pedal position, reaching about 30 km/h at the PCS alarm. Vehicle speed and distance to target at the alarm flag (ALM) and at times corresponding to three other system flags (PBA, FPB, and PB) were read from the Vehicle Control History records. Time to impact (TTI) at each flag was calculated and the distance between the stopped vehicle and the target was measured for each test.
Technical Paper

The Accuracy of Toyota Vehicle Control History Data during Autonomous Emergency Braking

Newer Toyota vehicles store information about more than 50 parameters for 5 s before and after non-collision events in the Vehicle Control History (VCH) records. The goals of this study were to assess the accuracy of VCH data acquired during Autonomous Emergency Braking (AEB) events and to investigate the effects of speed, acceleration, and system settings on AEB performance. A 2017 Toyota Corolla with Safety Sense P Pre-Collision System (PCS) was driven in a straight line towards a car-like target at different combinations of four speeds (20, 25, 30, and 40 km/h; or 12, 15, 19, and 25 mph) and three accelerator pedal positions (constant 30%, 40%, and 50% accelerator opening ratios) until the AEB system activated. The vehicle speed, vehicle acceleration, radar target closing speed, and radar target distance recorded in the VCH were compared to a reference 5th wheel. We found that errors in the VCH distance, speed, and acceleration data varied with the test conditions.
Technical Paper

Behavior of Toyota Airbag Control Modules Exposed to Low and Mid-Severity Collision Pulses

The repeatability and accuracy of front and rear speed changes reported by Toyota’s Airbag Control Modules (ACMs) have been previously characterized for low-severity collisions simulated on a linear sled. The goals of the present study are (i) to determine the accuracy and repeatability of Toyota ACMs in mid-severity crashes, and (ii) to validate the assumption that ACMs function similarly for idealized sled pulses and full-scale vehicle-to-barrier and vehicle-to-vehicle crashes. We exposed three Toyota Corollas to a series of full-scale aligned frontal and rear-end crash tests with speed changes (ΔV) of 4 to 12 km/h. We then characterized the response of another 16 isolated Toyota ACMs from three vehicle models (Corolla, Prius and Camry) and 3 generations (Gen 1, 2 and 3) using idealized sled pulses and replicated vehicle-to-vehicle and vehicle-to-barrier pulses in both frontal and rear-end crashes (ΔV = 9 to 17 km/h).
Journal Article

Comparison of the Accuracy and Sensitivity of Generation 1, 2 and 3 Toyota Event Data Recorders in Low-Speed Collisions

The accuracy of the speed change reported by Generation 1 Toyota Corolla Event Data Recorders (EDR) in low-speed front and rear-end collisions has previously been studied. It was found that the EDRs underestimated speed change in frontal collisions and overestimated speed change in rear-end collisions. The source of the uncertainty was modeled using a threshold acceleration and bias model. This study compares the response of Generation 1, 2 and 3 Toyota EDRs from Toyota Corolla, Camry and Prius models. 19 Toyota airbag control modules (ACMs) were mounted on a linear sled. The ACMs underwent a series of frontal and rear-end haversine crash pulses of varying severity, duration and peak acceleration. The accuracy and trigger thresholds of the different models and generations of EDRs were compared. There were different accuracy trends found between the early Generation 1 and the more modern Generation 2 and 3 EDRs.
Journal Article

Predicting Snowmobile Speed from Visible Locked-Track and Rolldown Marks in Groomed/Packed Snow Conditions

The ability to accurately calculate a snowmobile’s speed based on measured track marks in the snow is important when assessing a snowmobile accident. The characteristics and length of visible snowmobile track marks were documented for 41 locked-track braking tests and 38 rolldown tests using four modern snowmobiles on a groomed/packed snow surface. The documented track mark lengths were used to quantify the uncertainty associated with using track mark length to estimate initial speed. Regression models were developed for both data sets. The regression model of the locked-track tests revealed that using an average deceleration of 0.36g over the length of the locked track mark provides a good estimate of the best-fit line through the data, with the upper and lower 95th percentile prediction interval bounds best represented by using deceleration rates of 0.23g and 0.52g respectively.
Journal Article

Acceleration and Braking Performance of Snowmobiles on Groomed/Packed Snow

There are limited scientific data available on the acceleration and braking performance of modern snowmobiles. In this study we investigated the acceleration and deceleration characteristics of four modern snowmobiles of varying engine size (500 to 1000 cc) and style (2-stroke and 4-stroke) on groomed/packed snow conditions. The acceleration tests were performed at quarter, half and full throttle. The deceleration tests were performed using full braking with locked tracks and rolldown with power both on and off. Target test speeds ranged from 20 to 60 km/h. Snow condition parameters were measured throughout the tests. The results of the acceleration tests showed that at higher speeds, higher horsepower rating generally corresponds to higher acceleration rates, with a maximum observed average acceleration of 0.70g.
Technical Paper

Predicting Low-Speed Collision Descriptors using Dissimilar Collision Data

In low-speed collisions, motor vehicles can lose a significant fraction of their initial kinetic energy without plastic deformation or damping elements in their bumper assemblies. Five vehicles were subjected to multiple, non-damaging barrier and vehicle-to-vehicle impacts. Position, velocity, acceleration and force data were recorded for all collisions. Modeling vehicles as non-rigid two degree of freedom systems accurately predicted velocity and restitution responses for five vehicles in barrier and vehicle-to-vehicle impacts.

Human Subject Crash Testing

For more than 50 years, crash studies involving human subjects have improved understanding of occupant and vehicle kinematics, helped explain injury mechanisms in lower speed collisions, and led to improved seat and vehicle design. Human Subject Crash Testing: Innovations and Advances includes 42 of the most important historical and current studies which used living human subjects in frontal, side, and rear-end impacts. Covering more than 50 years of research (from 1955 through 2006), the book includes numerous landmark SAE papers, as well as papers from other conference proceedings. Papers were chosen based on criteria that included quality and rigor of methods, uniqueness, number of subjects, and long-term reference value. This book also features a comprehensive bibliography, which contains brief summaries of other relevant human subject crash test studies that are not included in the book.
Technical Paper

The Accuracy of Crash Data Saved by Ford Restraint Control Modules in Lowcspeed Collisions

Crash data recorded by the restraint control module (RCM) installed in newer Ford passenger vehicles have recently become available to investigators. To quantify the accuracy of the crash data in low-speed collisions, two RCM-equipped vehicles were exposed to 84 aligned frontal barrier collisions with speed changes up to 13.5 km/h. The accuracy of the speed change reported by the RCM ranged from an underestimate of 1.8 km/h to an overestimate of 0.3 km/h. The error varied with speed change. The RCMs were mounted on a linear sled to investigate their sensitivity to specific collision pulse parameters. For both RCMs, the first eight acceleration data points were duplicated at the end of the data and the record of the crash pulse was often incomplete. Based on the results of this study, crash investigators need to carefully interpret the RCM-reported acceleration and speed change data before using it to reconstruct low-speed collisions involving Ford vehicles.
Technical Paper

Threshold Visibility Levels for the Adrian Visibility Model under Nighttime Driving Conditions

Adrian's visibility model is a useful tool for assessing the visibility of an object at night. However, it was developed under laboratory conditions. Thus, it is necessary to determine the visibility levels which are required for detection under nighttime driving conditions. Experimental data from Olson et al were applied to the Adrian visibility model to determine visibility levels at target detection for alerted drivers. The data has been modified to account for experimental delay in the recorded detection points and a correction has been applied to assess driver expectation. Driver age, headlight beam pattern, and target reflectivity were all found to have a significant effect on visibility level at target detection. For alerted drivers, 50th-percentile threshold visibility levels between 1 and 23 were calculated. For unalerted drivers, 50th-percentile threshold visibility levels between 13 and 210 were calculated.
Technical Paper

The Accuracy and Sensitivity of Event Data Recorders in Low-Speed Collisions

Collision data stored in the airbag sensing and diagnostic module (SDM) of 1996 and newer GM vehicles have become available to accident investigators through the Vetronix Crash Data Retrieval system. In this study, two experiments were performed to investigate the accuracy and sensitivity of the speed change reported by the SDM in low-speed crashes. First, two SDM-equipped vehicles were subjected to 260 staged frontal collisions with speed changes below 11 km/h. Second, the SDMs were removed from the vehicles and exposed to a wide variety of collision pulses on a linear motion sled. In all of the vehicle tests, the speed change reported by the SDM underestimated the actual speed change of the vehicle. Sled testing revealed that the shape, duration and peak acceleration of the collision pulse affected the accuracy of the SDM-reported speed change. Data from the sled tests were then used to evaluate how the SDM-reported speed change was calculated.
Technical Paper

Human Cervical Motion Segment Flexibility and Facet Capsular Ligament Strain Under Combined Posterior Shear, Extension and Axial Compression

The cervical facet capsular ligaments are thought to be an important anatomical site of whiplash injury, although the mechanism by which these structures may be injured during whiplash remains unclear. The purpose of this study was to quantify the intervertebral flexibility and maximum principal strain in the facet capsular ligament under combined shear, bending and compressive loads similar to those which occur during whiplash loading. Two motion segments (C3-4 and C5-6) from seven female donors (50 ± P 10 years) were exposed to quasi-static posterior shear loads of 135 N applied to the superior vertebra on four occasions while under compressive axial preloads of 0 N, 45 N, 197 N and 325 N. Vertebral body motions and the full Lagrangian strain field in the right facet capsular ligament were measured using stereophotogrammetry. After flexibility testing, the right facet joint of each motion segment was isolated and failed in posterior shear.
Technical Paper

Tire Friction During Locked Wheel Braking

Accurate values of tire-roadway friction are an essential requirement for an accurate collision reconstruction. This paper presents updated tire friction data for three grades (economy, touring, and performance) of commercially-available tires under both wet and dry road conditions. Differences between tires and road conditions were tested using 540 locked wheel braking tests with a single passenger vehicle on a single road surface over six consecutive days. The vehicle was braked from about 60 km/h to a stop using a mechanical brake actuator to minimize variations in brake pedal application. These results showed differences between the friction measured with economy, touring and performance tires under wet and dry road conditions. Dry road friction values were higher than those reported previously in the literature using older model tires and these dry road friction values were normally distributed.