Is ESC left on during tests?
Yes. During emergency handling tests, all safety systems are engaged, including the stability control system.
At what speed is the GX going in the video?
Most vehicles can negotiate the corners of our handling track at about 50 mph. During the testing, however, we will drive faster before and after the corners. In the video, the GX was traveling approximately 60 mph when the throttle is lifted in order to slow the vehicle to make the corner.
Is there a deliberate steering action to induce oversteer?
No. During the normal course of the emergency handling testing, we test for each vehicle's ability to handle several different driver inputs. For instance, one of our tests includes lifting off the throttle in corners to see the vehicle's reaction. The Lexus GX performed poorly when the throttle is lifted in mid-corner. The oversteer was not induced by a steering action; the vehicle was being smoothly steered into the arc of the sweeping corner.
How do other SUVs perform in this test?
Over the years we have tested many SUVs with and without stability control, and we have not experienced such an abrupt and severe oversteer situation. Usually the front tires lose traction first.
What does this test illustrate?
This particular aspect of the test simulates the reaction of a vehicle if a driver enters a sweeping turn, such as an off-ramp, and lifts off the throttle to negotiate the corner. We look for a vehicle to have benign handling characteristics in this test, remaining predictable and controllable through the turn.
Shouldn't drivers be responsible for driving, rather than depend on vehicle electronics to protect them?
Even if the driver obeys the posted limits, that they may need to quickly slow down in a corner due to an obstacle in the road or a traffic backup. Our tests have shown that even vehicles without the protection of vehicle electronics like stability control don't exhibit the oversteer behavior that the GX did. Finally, many drivers lack the training to counter unexpected oversteer, and properly-calibrated stability control can still do that faster and more effectively than even a trained driver.
How do SUVs do in this test without ESC on?
We do not turn off the stability control system during emergency handling tests of SUVs. When testing sporty vehicles that might be used at a track event or autocross, we will shut off the system to evaluate performance.
How does sliding in this test equate to rollover danger?
Traveling sideways can lead to a tripped rollover if the vehicle goes off the road and hits a curb, a rut, or even digs into soft soil. Tripping in this way is the leading cause of rollover. Because the GX is a tall SUV with a high center of gravity, we feel the chance of a rollover is greater than with vehicles that are lower to the ground.
How does the Toyota 4Runner do in this test?
We tested the redesigned-for-2010 Toyota 4Runner at the same time as the GX 460. And while it is based on the same platform, it handled very differently. In the same tests, the 4Runner began to plow forward and the stability control quickly slowed the vehicle to maintain control. At no point did the rear of the car slide out.
Should CR issue a "Don't buy" for any vehicle without ESC?
While stability control is a very important safety feature and adds an extra margin of safety in many driving situations, most vehicles without stability control perform far better in our lift-off oversteer test than the GX 460. We will continue to assess vehicles with hands-on emergency handling tests rather than judging them on the mere presence or absence of safety features. The government has mandated that all vehicles have stability control as a standard feature for the 2012 model year.
