# Presentation: 484770

## Recent NHTSA Dynamic Rollover Testing Experience

**Dr. W. Riley Garrott**
***National Highway Traffic Safety Administration***
***Vehicle Research and Test Center***
**April 12, 2001**

**Recent NHTSA Dynamic Rollover Testing Experience**

## Presentation Overview

**Summary of Recent Testing**
**Test Maneuvers**
**Our Test Facilities**
**Repeatability**
**Outstanding Issues**

## Summary of Recent Testing

**NHTSA has been performing dynamic rollover testing steadily since fall of 1996**
**Isuzu Trooper investigation in 1996**
**Phase I-A research in 1997**
**Phase I-B research in 1997 – 98**
**Phase II research in 1998**
**Phase III research in 1999 – 2000**
**Ford Explorer investigation in 2000**
**Phase IV research in 2001**

## Dynamic Rollover Testing Video

**AVI Not Included**

## Test Maneuvers

**Two broad categories**
**Open-loop.  Handwheel steering angle is specified function of time**
** ****J-Turn**
** ****J-Turn with Pulse Braking**
** ****Fishhooks (reverse steer)**
** ****Resonant Steer**
** ****Single Sine **
**Each of above has many variations**

## Test Maneuvers

**Closed-loop.  Handwheel steering angle varies according to actions of vehicle**
**Driver closes feedback loop**
** ****Double Lane Change**
** ****Off-Road Recovery simulation**
**Instrumentation closes feedback loop**
** ****Fishhook with Roll Rate Feedback**

## Our Test Facilities

**VRTC located on the grounds of the Transportation Research Center, Inc.**
**Major automotive proving grounds**
**TRC’s Vehicle Dynamics Area – the large, flat paved area needed for dynamic rollover testing**
**Programmable steering controller**
**Rollover instrumentation suite**

## TRC’s Vehicle Dynamics Area

## Programmable Steering Controller

## Rollover Instrumentation Suite

## Repeatability

**During dynamic rollover testing, vehicles become highly non-linear**
**Small changes in inputs, test conditions can lead to large changes in test outcomes**
**Testing in early-70’s found up to 40% run-to-run variability**

## Repeatability

**Have had good repeatability in our testing**
**Major improvement over 70’s**
**Less tire wear with radial tires plus better equipment**
**Open-loop maneuver repeatability**
**Peak lateral accelerations – 0.05 g**
**Peak roll angles  – 0.5 degrees**
**Minimum speed for two-wheel lifts to occur  – ********2 mph**
**Closed-loop double lane change repeatability**
**Maximum traversal speed – ********10%**

## Issues

**Maneuver(s) to use for rollover ratings**
**Ensuring that cannot get good rollover rating by degrading vehicle handling**
**By putting tires with poor traction on a vehicle, can prevent two-wheel lifts in these maneuvers**
**Safety may be degraded because cannot turn as sharply**
**Use of two-wheel lifts as safety-relevant measure**
**Minor two-wheel lifts may not be safety issue**
**Requiring major two-wheel lifts may cause test driver safety problems**

## Issues

**Longer-term repeatability**
**Effects of weather of results**
** ****Summer versus winter**
**Changes to the same test surface with time**
**Reproducibility**
**Effects of testing on different test surfaces**

## Issues

**Outrigger effects**
**Must have for safety, prevention of test surface damage**
**How do they change a vehicles rollover propensity?**
**Tire wear**
**How much testing can be performed on a set of tires before wear effects become significant**
**Tire debeading**
**What to do if tires debead while performing rollover rating testing**