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Cutting Edge Testing For Rollover Cases: NHTSA’s Road Edge Recovery Maneuver

By Brian Chase on August 23, 2005 - No comments

By Brian D. Chase

I. Introduction:

For those of you who practice in the area of auto crashworthiness litigation, in particular rollover accidents, how many times have you heard the auto manufacturer, its experts, or a jury boldly proclaim some or all of the following: “This vehicle meets all Federal Motor Vehicle Safety Standards (FMVSS)”; “This vehicle complies with or exceeds all National Highway Traffic Safety Administration (NHTSA) guidelines or recommendations”; “NHTSA has investigated, or considered investigating, the alleged defect and determined that its not necessary to issue any new guidelines or safety standards”; and, “This vehicle passes the auto manufacturer’s rigorous stability and handling testing”? In addition to those proclamations, how many times have you had your vehicle stability experts criticized in deposition or on the witness stand as having “manipulated” their testing, that their testing it is not “objective” or “repeatable”, or that their testing is “merely a plaintiff’s test that has nothing to do with what happens in a real world accident”? Lastly, how many time have you heard, and this is the one that grates on me the most in a rollover case, the driver “panicked” and “over corrected” thereby somehow causing the vehicle to rollover unnecessarily and stating it was “driver error”?

Well folks, finally, those days are GONE!

NHTSA has recently adopted a dynamic rollover test to assess rollover propensity of light trucks/SUV’s — those vehicles with a gross vehicle weight rating under 10,000 pounds — to be used for its five-star consumer information rating program of 2004 model year vehicles. While the “NHTSA test” is not legally binding on a manufacturer from a compliance standpoint, nevertheless , now we can boldly proclaim to the auto industry, jury, or trier of fact that “this vehicle doesn’t pass NHTSA’s (the Government’s) rollover test”! Moreover, we can now criticize the manufacturer and their experts for not performing NHTSA’s test on their vehicles and brazenly assert that it is their testing that is “manipulated”, not “objective” or “repeatable”, or, better yet, “merely a manufacturer/defense test that has nothing to do with what happens in a real world real life accident.”

II. Historical Background:

NHTSA’s National Center for Statistics and Analysis reports that from 1991 to 2001 the total number of fatalities resulting from auto accidents, generally, has remained relatively stable, while the number of deaths resulting from rollover accidents has increased substantially. NHTSA observed that during this time period the number of occupants killed in all motor vehicle accidents increased by only 4 percent, while fatalities in rollover accidents increased 10 percent. NHTSA further noted that during this same time period passenger car occupant fatalities in rollovers declined 15 percent while light truck/SUV occupant rollover fatalities increased 43 percent.

Based on the foregoing trend, NHTSA began evaluating rollover testing in the 90’s. In 2001, NHTSA began publishing rollover rating information for consumers based primarily on a vehicle’s Static Stability Factor (SSF) (expressed mathematically as T/2H, which is the ratio of a vehicles track width to two times the center of gravity height), which is a non-dynamic rollover analysis.

At about this same time, the Transportation Recall Enhancement, Accountability, and Documentation Act (TREAD Act) required NHTSA to develop a dynamic test to assess rollover propensity for the purposes of: (1) implementing a consumer information program regarding vehicle stability; (2) carrying out a program of conducting such a test; and (3) conducting a rulemaking process to determine how best to disseminate stability test results to the public.

On July 3, 2001, NHTSA published a Request for Comments notice announcing that it was going to evaluate a number of dynamic driving maneuver tests for rollover resistence and then develop or adopt a dynamic rollover test for light trucks/SUV’s.

On October 7, 2002, NHTSA published a Notice of Proposed Rulemaking proposing alternative ways of using various dynamic maneuver test results in consumer information regarding the rollover resistance of new vehicles.

The culmination of this work has resulted in NHTSA’s adoption of a dynamic rollover test to assess rollover propensity of light trucks/SUV’s to be used for its five-star consumer information rating program beginning with the 2004 model year vehicles. The dynamic test NHTSA adopted is called the “fishhook” maneuver. The results from this test and the vehicle’s SSF will be combined to determine a predicted rollover rate. The predicted rollover rate is to be translated into a five star rating system which is the same as the prior star rating system that was in use: One star indicating a vehicle’s rollover rate at greater than 40 percent; two stars indicating a vehicle’s rollover rate at between 30 and 39 percent; three stars indicating a vehicle’s rollover rate at between 20 and 29 percent; four stars indicating a vehicle’s rollover rate at between 10 and 19 percent; and five stars indicating a vehicle’s rollover rate at 10 percent or less.

III. Fishhook/Road Edge Recovery Maneuver:

NHTSA evaluated various auto manufacturers’ stability and handling testing ranging from computer modeling to on-road dynamic testing. NHTSA was looking for a test which offer the highest levels of: (1) true vehicle limits testing; (2) objectivity; (3) repeatability; and (4) discriminatory capability. NHTSA was critical of most of the industry’s proposals for violating one and usually more of the four these objectives.

Ultimately, NHTSA decided to adopt the fishhook maneuver as it was found to be the only true dynamic maneuver that tested the true limits of the vehicle with regard to rollover propensity along with meeting NHTSA’s objectives. The test gets its name from its literal resemblance to a fisherman’s hook: a test driver travels in a straight line and makes a single lane change to the left or right. The driver then makes a sharp and sudden turn in the opposite direction, holding the steering wheel in this position until the vehicle comes to rest.

Initially, NHTSA re-named the fishhook maneuver to the “Road Edge Recovery Maneuver”. NHTSA reasoned:

NHTSA analysis of crash databases have found that the most common scenario leading to untripped rollover is road edge recovery. This scenario begins with the vehicle dropping two wheels off the right edge of the paved roadway onto an unpaved shoulder….The driver attempts to regain the paved roadway by steering to the left. Due to the lip between the pavement and the shoulder, a substantial steer angle is required to start the vehicle moving to the left. However, once the vehicle overcomes the lip and starts moving, it quickly threatens to depart from the left side of the road. Therefore, the driver rapidly countersteers to the right. (67 Fed.Reg. at 62539 (October 7, 2002) [emphasis added].)

This is exactly what happens to the vast majority of our clients involved in a rollover accident and NHTSA’s research, analysis, and reasoning here provides us with great arguments showing that our client, or the driver of the vehicle, did nothing “unreasonable” once they were confronted with this very serious emergency situation, a situation, quite frankly, only made serious due to the inherent instability of most of today’s light trucks, SUV’s and 15 passenger vans. For example, NHTSA’s analysis shows that a driver drifting two wheels off the edge of the roadway onto the shoulder is not something unforeseeable, aberrational, or even unlikely, as NHTSA correctly points out it is the “most common scenario” of how untripped rollovers occur.

Next, NHTSA’s analysis, (i.e., the Government’s Traffic Safety Administration) shows that the argument that the driver of the vehicle was negligent by “overcorrecting” or “overreacting” either when trying to re-enter the roadway or after re-entering the roadway lacks merit, because once again, NHTSA correctly points out this occurrence is the “most common scenario” leading to an untripped rollover, in part because “a substantial steer angle is required to start the vehicle moving left.” Lastly, this “most common scenario” confirms and bolsters exactly why consumer attorneys have been advocating this type of rigorous real world dynamic test all along. As NHTSA points out: “This decision maximizes the vehicle information used to make the rollover rate prediction and will allow us to ensure that rollover…information corresponds even more closely to real-world rollovers.” NHTSA Docket NHTSA-2001-9663, Notice 3, RIN 2127-AI81, page 5. The results from this type of testing also confirm why the auto manufacturers don’t like it and don’t use it because it shows many of their vehicles are inherently unstable and prone to rollover.

At the last minute due to intensive lobbying efforts from the manufacturers, NHTSA changed the name of this test from “Road Edge Recovery Maneuver” back to “fishhook”. The industry did not like the name of the test because it was too-close-to-home with regard to how these accidents occur in the real world under real world accident facts. They would much rather describe the test as fishhook rather than Road Edge Recovery Maneuver. Keep this in mind when examining industry witnesses after they testify the fishhook maneuver is not a real world accident pattern maneuver.

A. How The Test Is Run:

  1. Speed:
    The entrance speeds begin at 35 mph and are increased in 5 mph increments up to 50 mph or until the test is terminated due the vehicle achieving simultaneous two wheel lift of two inches or greater. If two wheel lift is attained, then a downward iteration of vehicle speed is used in 1 mph increments until such lift is no longer attained. When two wheel lift is detected, then the test is run two additional times at that speed to determine if two wheel lift is repeatable.
  2. Loading Conditions:
    The test is conducted using two different loading conditions. The light load is a test driver plus instrumentation in the right front passenger seat which equates to two occupants, a driver and front seat passenger. For vehicles capable of carrying five occupants or more, three water dummies were used weighted to 175 lbs., plus instrumentation which was considered the heavy load. If a vehicle attained two wheel lift with the light load condition, the test was not run at the heavy load. This makes sense because usually the more passengers you have in a vehicle the center of gravity increases and rollover resistance is decreased.
  3. Steering Inputs:
    The steering inputs utilized for this test are designed is to simulate the steering a driver might use acting in an emergency road edge recovery situation. The steering inputs are performed using an automated steering controller to make the test more objective and eliminating the subjective feel a test driver can add to their steering inputs to manipulate test results. Additionally, the reverse steering input (countersteer), is timed to coincide with the maximum roll angle of the vehicle in order to create the “worst case” scenario with regard to rollover potential. The steering wheel rates are performed at 720 degrees per second.

The initial steering input is calculated to place a steady lateral acceleration of 0.3 g on the vehicle at 50 mph. This averages out to approximately a steering input of 270 degrees on most vehicles. The dwell time – the time between completion of the initial steering input and the initiation of the countersteer – are defined by the roll motion of the vehicle, i.e., however long it takes to attain the approximate maximum roll angle of the vehicle, which is determined by the steering machine which monitors the vehicle’s roll rate. If the initial steering input is to the left, then the reverse steering input is performed when the roll rate of the vehicle first equals or goes below 1.5 degrees per second. If the initial steering input is to the right, then the reverse steering input is performed when the roll rate of the vehicle first equals or exceeds 1.5 degrees per second.

IV. Static Stability Factor (SSF):

As stated above, in addition to using the fishhook maneuver, NHTSA chose to also utilize information taken from a vehicle’s SSF to assist in evaluating rollover propensity. While consumer attorneys have always believed in the validity and use of such a measurement, the auto industry has always deemed that SSF as a measure of rollover resistance as being too simplistic and opposed its use because it did not include the effects of suspension deflections, tire traction and electronic stability control (ESC). However, once again, NHTSA disagreed with the industry party line noting:

Congress…directed the agency to fund a National Academy of Sciences (NAS) study on vehicle rollover ratings. The study topics were “whether the static stability factor is a scientifically valid measurement that presents practical, useful information to the public including a comparison of the public including a comparison of the static stability factor test versus a test with rollover metrics based on dynamic driving conditions that may induce rollover events.” The National Academy’s report was completed and made available at the end of February 2002.

The NAS study found that SSF is a scientifically valid measurement of rollover resistance for which the underlying physics and real-world crash data are consistent with the conclusion that an increase in SSF reduces the likelihood of rollover. It also found that dynamic tests should compliments static measures, such as SSF, rather than replace them in consumer information on rollover resistance. The dynamic tests that NAS recommended would be driving maneuvers used to assess “transient vehicle behavior leading to rollover.” (NHTSA Docket NHTSA-2001-9663, Notice 3, RIN 2127-AI81, at 12 [emphasis added])

Here we have another blow to the auto industry, straight from the Government’s mouth, that a rollover resistence measurement that consumer attorneys have been advocating for years is in fact, scientific, valid, and does correspond to real world accident data.


Finally, for those of us who do rollover cases, we can now have our experts perform a dynamic rollover test that can’t be attacked as “merely a plaintiff’s test that has nothing to do with what happens in a real world accident.” We now have a test which has been adopted by the National Highway Traffic Safety Administration as being a real world, real life test to demonstrate what happens to our clients in real world rollover accidents. Furthermore, our experts can’t be attacked as having “manipulated” their testing or that their testing it is not “objective” or “repeatable.” And, finally, we now have some ammunition against the argument that our clients, or the drivers of the vehicles they were riding in, “panicked” and “over corrected” thereby somehow causing the vehicle to rollover unnecessarily and stating it was “driver error.” NHTSA has now provided us with the analysis that these types of situations and reactions thereto are normal, expected and foreseeable, not careless, negligent and unforeseeable.

Lastly, the static stability factor has now more than ever been endorsed by NHTSA as a valid rollover resistance measurement that is scientific and valid and corresponds to real world accident data.

Posted in: Car Accidents

About the Author: Brian Chase

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