Collision: The International Compendium for Crash Research
ollision C The International Compendium for Crash Research
Volume 1 Issue 1
Accuracy of Speed Recorded by an SDM & the Effects of Brake & Yaw Events Analysis of the GM Sensing & Diagnostic Module in 360 Degree Linear Momentum Collisions: Real Case Analysis CDR Data Presentation & Validation in Legal Proceedings
A Review of Various ACM Module Types & Data Recorded Volume 1, Issue 1 - June 2006
Implementing Policy for CDR Incorporating CDR Services in an Existing Forensic Practice Motorcycle Collinear Collisions Involving Motor Vehicles Equipped with EDRs
Premier Issue Case Study:
Crash Data Retrieval CDR Conference Proceedings Event Calendar Organization News
Includes CD 2006 CDR User’s Conference
www.CollisionPublishing.com
If you found this article useful, look into a subscription to Collision Magazine at www.CollisionMagazine.com
Find out more about the next EDR User’s Summit at EDRSummit.com
Contents june 2006
of interest 2
From the Editor
4
Calendar of Events
6
Organization News
8
Letter From NAPARS
On The Cover Photo By: Scott Baker Taken at the Bremerton Race Track in Washington at the 2002 ARCCSI Crash Conference. This was approximately a 52 MPH collision. Trivia: This photo was used as the framework for the ARC-CSI logo.
features 9
The Accuracy of Speed Recorded by an SDM and the Effects of Brake, YAW and other Factors
17
Analysis of the GM Sensing and Diagnostic Module in 360 Degree Linear Momentum Collisions
43
CDR Presentation and Validation in Legal Proceedings
53
A Review of Various ACM Module Types and Data Recorded
56
Rational Legislative and Organizational Policy for Automotive Event Data Recorders
69
Practical Ascpects of CDR Using the Vetronix System
82
Motorcycle Collinear Collisions Involving Motor Vehicles Equipped with EDRs
case study 28
Crash Data Case Study
97
Case Study Solution
28
The Accuracy of Speed Recorded by an SDM and the Effects of Brake, Yaw and Other Factors -Timothy J. Reust, James M. Morgan Accident Science, Inc.
to evaluate the event.To date, only a limited study of the SDM-reported Many 1999 and newer speed accuracy has been reported by General Motor vehicles Lawrence. have an event data recorder (EDR) that can record data which NTRODUCTION includes pre-event speed. The EDR is incorporated into the air bag Late model General Motors system sensing and diagnostic module vehicles incorporate an (SDM). In this study, the accuracy of event data recorder with the vehicle-reported speed was tested the sensing and diagnostic module. during acceleration, coasting, braking The SDM can record pre-event and yaw at speeds between 1 to 90 speeds at one-second intervals for miles per hour. The accuracy was approximately five seconds preceding also tested during heavy acceleration, the event. The speed is in units of when an undersized spare tire was miles per hour and is recorded in 1 mounted on the drive axle and with mile per hour increments. Other tires having new and worn tire tread information recorded by the SDM depths. The vehicle-reported speed includes, engine RPM, throttle was compared to the speed measured percent and brake application. The by a calibrated GPS speed measuring recorded event can be triggered by system. The results showed that the air bag deployment or a deceleration. vehicle-reported speed matched well The vehicles used for this study were during acceleration and coasting, manufactured by General Motors and underestimated the speed during included both front wheel drive and braking and underestimated the speed rear wheel drive. This information during a yaw event. Information can be downloaded using the Vetronix downloaded from a SDM after Crash Data Retrieval (CDR) kit. an accident event can be used in conjunction with conventional The current trend in accident methods of accident reconstruction reconstruction is to make use of the
A
BSTRACT
I
available electronic data. The data can make a significant contribution to the engineering reconstruction of a vehicle accident. In some cases, the SDM data can provide information that traditional methods cannot. This paper addresses the accuracy of the SDM-reported speed and the affects of brake, acceleration and yaw events.
M
ETHODS
A series of well-documented tests were conducted with various types of vehicles. The testing included 12 different vehicles which included both front and rear wheel drives. The vehicle included passenger type, SUV, pickup and minivan. Some of the vehicles were equipped with the StabiliTrak electronic stability control system. All the testing was conducted on dry and level roadway surfaces. The tires of the vehicles were the original equipment size and were inflated to their recommended pressures. More than 80 instrumented tests were conducted for this research paper. Some of the testing was done by slowly accelerating the vehicle up to speed, others with maximum acceleration and Collision
some also included coasting and was done for the purpose of checking the accuracy of the vehicle-reported speed versus an instrumented speed. The brake testing speeds ranged from 15 to 90 miles per hour. The majority of the brake tests were conducted with the ABS brake system active, however some were with the system deactivated. Most of the brake tests were conducted with maximum brake application and some tests were done within the normal range of brake application. The yaw testing was conducted with and without brake application. A few tests were conducted with heavy acceleration induced wheel slip. Testing was also conducted with an undersized spare tire which was obtained from a vehicle and mounted to its drive axle.
V
ehicles
The following vehicles were used during the testing:
A. 2001 Buick Regal B. 2002 Chevrolet Venture. C. 2002 Chevrolet Camaro SS (manual transmission) D. 2004 Pontiac Bonneville E. 2005 GMC Yukon XL (with StabiliTrak) F. 2005 Chevrolet Suburban (with StabiliTrak) G. 2005 GMC Sierra Z71 H. 2005 Pontiac Bonneville I. 2005 Pontiac Bonneville J. 2005 Chevrolet Trailblazer K. 2005 Buick Le Sabre L. 2005 Cadillac Deville
I
NSTRUMENTATION
Vehicle speed was measured using a Racelogic VBox III GPS system .The VBox system has a speed accuracy of 0.063 mph averaged over four samples. Collision 10
The Racelogic (IMU) inertial measurement unit was used during the yaw tests to measure yaw rate and lateral acceleration. The VBox also recorded brake and throttle data. The initiation of brake pedal application was recorded by placing a tape switch on the surface of the brake pedal. Throttle sensor position information was measured by placing wire taps onto the leads of the vehicle’s throttle position sensor
and provided a relatively smooth data line. The difference between the VBox speeds at both the beginning and end of the step was used as the vehicle-reported speed error. (Figure 1) For the brake tests and yaw tests a percent error was calculated between the VBox speed (actual speed) and the Tech 2 (vehicle-reported speed). The tests of the tires with worn and new tread depth were compared and used to show the variation in speed accuracy.
The instrumentation signals were ESULTS recorded by the VBox system. The vehicle-reported speed and additional The low acceleration tests engine and running gear data were provided data at speeds recorded as a snapshot through the between 1 to 76 miles per vehicles’ data link connector using hour and were combined together in a the Vetronix Tech 2. common graph. Based on this testing,
R
Each test produced two data sets: the instrumentation data (VBox) and the snapshot data (Tech 2). The data acquisition system of the VBox records 100 samples per second. The Tech 2 recorded a snapshot with approximately 3 to 10 samples per second
D
ATA REDUCTION
The throttle sensor data from both the VBox data acquisition and the Tech 2 snapshot were used as the common trace to synchronize the two data sets together. The VBox speed was used to be the actual speed of the vehicle. After the recorded data was synchronized, the VBox speed and the snapshot speed from each test were evaluated. For the low acceleration, coasting and tire tread depth tests, the vehicle-reported speed provided several data points at one speed and then would “step” to the next mile per hour value. During that time the VBox speed was constantly changing
the speed accuracy is ±1.5 mile per hour during low acceleration. (Figure 2)
The coasting tests were conducted at speeds between 24 to 70 miles per hour and were combined in a common graph. Based on this testing, the speed accuracy is +0.5 to -2.0 miles per hour during coasting. (Figure 3) The maximum acceleration tests were conducted at full throttle (100%) using the 2002 Chevrolet Camaro SS (rear drive with 5.7 liter LS1 engine) and the 2005 Pontiac Bonneville (front drive with 3.8 liter engine). The results show that speed errors are generally within the ±1.5 mile per hour except during initial takeoff and gear shifts. The graphs show the maximum error at each speed. (Figures 4 and 5) The maximum effort brake with ABS tests showed the vehicle-reported speed is underreported by approximately 8 to 18 percent at vehicle-reported speeds of 30 miles per hour and higher. The exception to this upper range was the pickup which had an error of 25 % which would occur briefly at approximately 0.28 seconds after brake application. A common trend