Drivers: Don’t Be Slow To React, Truck ESC Recall

September 22, 2011 by · Leave a Comment
Filed under: News 

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

September 19, 2011 by · Leave a Comment
Filed under: Crash Reconstruction, Testing 

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.

Fire Suppression in Buses and Coaches

September 15, 2011 by · Leave a Comment
Filed under: Random, Testing 

According to the brandposten (English edition) the number of fires in buses and coaches has more than doubled since the end of the 1990s.  As a result many Buses and Coaches are now equipped with automatic fire suppression systems in the engine compartment.  The brandposten goes on to describe a test method for evaluating fire suppression systems.  There was an interesting recall on this topic in which a fire suppression system in certain Glaval Buses was incorrectly made with the discharge nozzles incorrectly placed in the driver’s area.  The consequence was described: “In the event of a system discharge, a significant cloud of powder could be released into the driver’s compartment possibly obstructing the driver’s view. This situation could result in a vehicle crash.”

The Take Away on Rollover Drag Factors

September 13, 2011 by · Leave a Comment
Filed under: Crash Reconstruction 

Dolly rollover tests suggest that the appropriate drag factor range for use in rollover reconstruction, excluding special circumstance, is 0.38 to 0.50.  The finding is from the calculated results of 81 dolly rollover crash tests statistically trimmed to exclude the upper and lower 15 percent.

Reevaluation of roll phase analysis of rollover tests on an actual highway found lowered average roll phase drag factors.  The average roll phase drag factor as published in the papers was 0.53 g (min = 0.39, max = 0.74) and the average reevaluated drag factor was 0.45 g (min = 0.36, max = 0.52).  Natural rollover tests suggest the appropriate drag factor range, excluding special circumstances, is 0.39 to 0.50.  The finding is from the calculated results of 21 naturally occurring rollover crash tests statistically trimmed to exclude the upper and lower 15 percent.

Getting Rollover Drag Factors Right

September 12, 2011 by · Leave a Comment
Filed under: Crash Reconstruction 

A comparison was conducted of numerous historical studies by reexamination of the original works, analysis of their data, and centralized compilation and analysis of their results. In total 81 dolly rollover crash tests, 24 naturally occurring rollover crash tests, and 102 reconstructed rollovers were identified.  Of the 24 naturally occurring tests 18 were steer induced rollover tests.

The range of drag factors for all examined dolly rollovers was 0.38 g to 0.50 g with the upper and lower 15 percent statistically trimmed.  The average drag factor for dolly rollovers was 0.44 g (Standard Deviation = 0.064) with a reported minimum of 0.31 g and a reported maximum of 0.61 g.   The range of drag factors for the set of naturally occurring rollovers was 0.39 g to 0.50 g with the upper and lower 15 percent statistically trimmed. The average drag factor for naturally occurring rollovers was 0.44 g (Standard Deviation = 0.063) with a reported minimum of 0.33 g and a reported maximum of 0.57 g.

Reevaluation of roll phase analysis published in two papers reporting results of rollover tests on an actual highway (Asay, 2009 and 2010) found lowered average roll phase drag factors as shown in table 1.  The average roll phase drag factor published in the papers was 0.53 g (min = 0.39, max = 0.74) and the average reevaluated drag factor was 0.45 g (min = 0.36, max = 0.52).  Reevaluation was performed from data published in the papers. A final analysis should be conducted using the actual test data.

Published results of reconstruction derived roll phase drag factors (Hight, 1972) between 0.40 g and 0.65 g was confirmed as the range representing the middle 60% of pre-1972 reconstructed rollover crashes on flat ground, figure 3. The reconstructed drag factors were in a range of 0.04 g to 1.20 g for all 102 plotted results, including downhill rollovers and rollovers with vertical drops.  For rollovers on flat ground the reconstructed range was 0.21 g to 0.83 g.

Sudden Acceleration in Reverse

September 8, 2011 by · Leave a Comment
Filed under: Crash Reconstruction 

I ran across an interesting recall this morning.  It is interesting because it points to potential for problems with software in the control modules of key safety systems.  The recall summary is:

“Honda is recalling certain model year 2011 CR-Z passenger cars with manual transmissions, manufactured from January 8, 2010, through June 27, 2011.  Should the engine stall while the brake pedal is not pressed, there is a possibility that the engine control unit (ECU) software may cause the electric motor of the hybrid system to move the vehicle unexpectedly in the opposite direction of the selected gear.”

Essentially this Honda recall identified a defect that results in sudden acceleration in the opposite direction of intended travel – sudden acceleration in reverse.

This is not the only recent recall on this issue: Buick Lacrosse’ were recalled because an improper diagnosis:

“may cause the ESC to falsely activate, resulting in sudden changes in vehicle handling and deceleration, particularly at higher speeds, which may cause the driver difficulty in maintaining the vehicle’s desired path of travel and desired vehicle speed, and could result in a crash without warning.”

Essentially the Lacrosse recall identified a defect that may result in brakes application on one side of a vehicle while it is traveling at highway speeds – sudden acceleration to the left (or right).