Drivers: Don’t Be Slow To React, Truck ESC Recall
A recent Recall by Daimler Trucks of 2006 to 2012 Freightliner Trucks highlights recent concern regarding inadvertent actuation of Electronic Stability Control (ESC) Systems. Potentially 47,000 units are recalled with Meritor Wabco ESC system manufactured since September of 2005. According to the recall summary, “Under certain road and driving conditions, vehicle body roll and road inclination characteristics may adversely affect the slip angle calculation of the Eectronic Stability Control (ESC) system. This might cause the ESC to perceive an over steering situation and therefore apply the outer wheel brake on the front axle until the vehicle is perceived to be stable.” The Meritor Wabco technologies include ESC, Roll Stability Control and trailer stability control. Some of these systems are described in the Meritor literature as being available since 2002.
Interesting that the vehicle based risk to motor vehicle safety (the recall) lists the defect’s consequence as, “If the driver is slow to react during this ESC intervention, the vehicle may deviate from the intended line of travel increasing the risk of a crash.” In other words, the manufacture is saying they are responsible for an unexpected and dangerous external disturbance to the vehicle – presumably a disturbance from no driver input – but the increased risk of a crash occurs if the driver is slow to react??
NHTSA Published Update of ESC Analysis
The August 10, 2011 Federal Register contained NHTSA’s updated statistical analysis on its existing Safety Standard 126, Electronic Stability Control Systems. The report’s title is: Crash Prevention Effectiveness in Light-Vehicle Electronic Stability Control: An Update of the 2007 NHTSA Evaluation. The Notice stated:
“Statistical analyses based on data for calendar years 1997 to 2009 from the Fatality Analysis Reporting System (FARS) and the General Estimates System (GES) of the National Automotive Sampling System (NASS) estimate the long-term effectiveness of electronic stability control (ESC) for passenger cars and LTVs (light trucks and vans). Safety Standard 126 establishes standards for electronic stability control systems manufactured for use in light vehicles. This report is an update of a previous NHTSA analysis of ESC effectiveness (72 FR 41582) published in 2007.”
“The principal findings are that ESC was associated with a six percent decrease in the likelihood that a vehicle would be involved in any police reported crash and an 18 percent reduction in the probability that a vehicle would be involved in a fatal crash. For passenger cars, the reductions are 5 percent and 23 percent, respectively; for LTVs, 7 percent and 20 percent. Each of these reductions is statistically significant except for the 5 percent overall effect in cars.”
Comments from the public are solicited and must be received by December 8, 2011.
Correcting the Record on NA Luxury Brand ESC Implementation
The North American (NA) implementation of Electronic Stability Control was detailed in the 2008 Society of Automotive Engineers (SAE) paper “Industry Implementation of Automotive Electronic Stability Control (ESC) Systems,” by Nicholas Durisek and Kevan Granat of Dynamic Analysis Group LLC. The Paper compares the luxury vehicle brands Mercedes, BMW and Lexus/Toyota and draws conclusions based upon this comparison. The problem is that Lexus/Toyota is two different brands owned by one manufacture and only Lexus is a luxury brand.
Automotive News Data records, in 2002 Toyota sold 1,756,127 vehicles in the United States; Lexus accounted for 234,109 sales. Also in 2002, the BMW division of the BMW group sold 232,032 vehicles and Mercedes sold 213,225 vehicles.
Comparing Mercedes, BMW and only Lexus passenger cars reveals a disturbing and diverging trend in ESC as standard equipment implementation rates beginning in 1998. Mercedes and BMW were essentially at zero implementation prior to 1998 and 100% implementation for 2000 and on, while Lexus using yearly sales recorded in Automotive News Data had ESC implemented as standard equipment in its passenger cars at the rate of 43% in 2000, 40% in 2001, 39% in 2002 and 37% in 2003. Mercedes and BMW saw the value of ESC and quickly implemented the technology in their entire North American fleet. Lexus missed the opportunity of ESC and delayed full standardized implementation by at least 8 years.
Comparing Mercedes, BMW and only Lexus, instead of Lexus and Toyota together, reflects a Toyota marketing strategy that left many Lexus owners with far inferior vehicles when it came to the benefits of ESC. ESC has been described as providing safety benefit second only to seatbelts. The underlying technology of using individual wheel brake application intervention when drivers lose control of their vehicles began development at Bosch in the late 1980s and was first commercialized in their home countries by Toyota and Mercedes in 1995.
According to Durisek and Granat, “Mercedes’ implementation included less than 2000 vehicles for each of the first three years an ESC system was offered, 1996 through 1998. Those units amounted to less than 2% of the total number of vehicles sold by Mercedes. By model year 2000, Mercedes equipped all models with an ESC system as standard equipment except the SLK. An ESC system was not available on the SLK until 2001…. Implementation by BMW similarly began with relatively low volumes in 1998 and was increased to 100% by model year 2001…. Toyota’s North American implementation of ESC systems as standard equipment began with its Lexus brand in 1998 and included over 50,000 units, more than any other manufacturer for that model year. In model year 2006, the number of Toyota vehicles with an ESC system as standard equipment was over 640,000 units, more than double the number of units sold by Mercedes or BMW.”
Durisek and Granat concluded, “The phase-in of ESC system technology by lower volume manufacturers (i.e. luxury brands) took five to six years before having 100% ESC system implementation into their vehicle lines.” However, according to the Durisek and Granat data, BMW’s North American implementation of ESC as standard equipment took four years with over 95% implementation in three years (by 2000). Mercedes’ implementation of ESC as standard equipment took six years with almost 95% implementation in five years (by 2000). Mercedes had less than 2% implementation in 1998, almost 95% standard equipment implementation in 2000 and in 2001 was at 100% implementation. Not to ignore the importance of full implementation, but Mercedes went from essentially zero to almost complete in two years. For both BMW and Mercedes the final standard implementation of ESC was on a single model with low production. Lexus began implementation in 1998, and completed implementation of ESC as standard equipment in 2007, a full ten years. The last Lexus model with ESC standard was its highest production volume ES line which in 2002, according to the Automotive News Data, accounted for 71,450 Lexus sales – almost half of all Lexus passenger cars sold in 2002.
Will Electronic Stability Control Eliminate Tire Tread Separation Crashes?
By Mark Arndt
Will Electronic Stability Control Eliminate Tire Tread Separation Crashes?
Probably not, but the technology holds great promise to substantially reduce these crashes. Recently published testing results demonstrate that Electronic Stability Control (ESC) systems provide drivers a greater steering margin of safety when their vehicle experience a rear tire tread separation.
The study also found that not all ESC systems are alike in their potential benefit. Some systems provide a greater benefit to the driver in the event of a rear tire tread separation than others.
A rear tire tread separation event can lead to loss of vehicle control as a result of an unexpected deviation to the vehicle’s intended path in combination with significant change that occurs to the vehicle’s steering characteristics. Vehicle designers have had difficulty providing substantial improvements in basic vehicle response after a tire tread separation, but ESC was shown to make a substantial improvement in rear tire failure events (video).
Black Box Proven Accurate and Valuable to Crash Reconstruction
By Mark Arndt
A paper recently published at the 2009 SAE World Congress demonstrates the accuracy and utility of speed data collected by the Powertrain Control Module (PCM) of late model Ford vehicles. Testing described in the paper was completed in conjunction with an evaluation of Electronic Stability Control (ESC) systems supported by Tab Turner of the law firm Turner & Associates.
An instrumented 2005 Ford Explorer was used to evaluate speed data provided from its PCM at high slip angles and other dynamic maneuvers. The slip angle is the angle between the heading of a vehicle and its velocity direction –- a vehicle that is side-slipping or spinning out has a high slip angle.
PCM speed was compared to speed and slip angle collected from a calibrated velocity sensor. In addition to speed, slip angle and other standard handling test measurements the vehicle brake switch and throttle were recorded so PCM data could be synchronized. After each test run the vehicle ignition was turned off and the PCM was downloaded using commercially available Bosch hardware and software. The principal maneuver was the National Highway Traffic Safety Administration (NHTSA) sine-with-dwell test consisting of a 0.7 HZ sinusoidal steer with a 0.5 second dwell at the steer reversal peak.
Runs were conducted with the vehicle’s Electronic Stability Control (ESC) disengaged so that the test vehicle would achieve large slip angles. Other dynamic maneuvers included: NHTSA’s sine-with-dwell with ESC engaged; 100% accelerator to 80 mph with 0.5G braking to stop; and acceleration to 50 mph with maximum ABS braking to stop.
Results demonstrate agreement between the speed recorded by the calibrated instrumentation and speed recorded by the vehicle’s PCM for conditions when the vehicle slip angle and rear wheel slip were near zero. PCM speed was lower than instrumented speed in high slip angle maneuvers. PCM on average underreported during maximum ABS braking and at medium to high speed in 0.5G braking. In acceleration the PCM speed had no detectable under-reporting error except at the highest speeds with 100% accelerator application.
Mark W. Arndt
