Another Look at Electronic Stability Control

Thomas McMahon
Posted on January 27, 2017
This photo from the National Transportation Safety Board shows a curve in Talley Road in Chattanooga, Tennessee, at the site of the Nov. 22 fatal school bus crash.
This photo from the National Transportation Safety Board shows a curve in Talley Road in Chattanooga, Tennessee, at the site of the Nov. 22 fatal school bus crash.

The phone rang, and I looked down at the caller ID: “CHATTANOOGA TN.” I immediately knew the awful reason for the call, if not who the caller was.

It was Tuesday, Nov. 22, the morning after the devastating school bus crash in Chattanooga, Tennessee, in which six students were killed and many more were injured. The crash attracted an onslaught of coverage in the nation’s media outlets, the initial wave of which was filled with much uncertainty and even some exaggerated details. For example, one early news story reported that “at least 12 people died.”

But on Tuesday morning, more reliable facts about the crash had been released by police in Chattanooga. The investigation was in full swing, and a clearer picture of the event was emerging.

I answered the phone and was greeted by a reporter from the Chattanooga Times Free Press. As expected, he was calling to talk about the previous day’s school bus crash.

What surprised me about this reporter’s questions was that he didn’t narrow in on the seat belt issue, as many other media outlets did. (The bus in the crash didn’t have seat belts, which aren’t required on Tennessee school buses.)

Instead, the reporter was more interested in asking about a technology that can help prevent crashes: electronic stability control (ESC).

For the uninitiated, ESC systems have sensors that monitor vehicle movement and steering. They can help mitigate rollover incidents by using automatic computer-controlled braking, and they can aid the driver in addressing severe under-steer or over-steer conditions that can lead to loss of control.

In 2015, the National Highway Traffic Safety Administration (NHTSA) issued a final rule that will require ESC systems on heavy trucks and some large buses, such as motorcoaches, but the agency exempted school buses.

During the proposal phase of that rulemaking, some organizations — including the National Transportation Safety Board — called for an ESC mandate for all buses greater than 10,000 pounds, including school buses. But NHTSA cited federal data showing that most school bus crashes are not rollover or loss-of-control crashes that ESC systems are capable of preventing.

“For these reasons, we will not require school buses to be equipped with ESC at this time,” NHTSA said in the final rule, which was published in June 2015.

Interestingly enough, just two weeks before the Chattanooga crash, a NHTSA official revealed that the agency was reconsidering its decision.

At the National Association of State Directors of Pupil Transportation Services conference on Nov. 8, NHTSA Program Analyst Brian Chodrow said the agency is taking another look at ESC for school buses. He said the technology wasn’t found to be cost-effective for school buses at the time of the rulemaking, but that is likely to change now that the large school bus OEMs offer ESC as an option.

Chodrow said that the topic was “something we’ll be looking at closely,” and left it at that “hint,” as he put it.

That came to my mind two weeks later, as I reviewed the details of the Chattanooga crash. According to investigators, the school bus departed the roadway to the right, took out a mailbox, veered to the left, struck a utility pole, rolled onto its right side, and then crashed into a tree. The posted speed limit on the road was 30 mph, with a lower advisory speed for curves, and police estimated that the bus was traveling around 50 mph.

Coincidentally, just three days before the Chattanooga crash, another school bus in Tennessee — this one taking students to Opryland in Nashville on Nov. 18 — rolled over after the driver reportedly lost control and overcorrected. Fortunately, the injuries in that crash were not life-threatening.

As I told the reporter from the Chattanooga Times Free Press, I can’t say how the outcome of the Chattanooga incident might have been different if the bus had been equipped with ESC. But the technology has proven to be effective on various types of vehicles, large and small, and I’ve test-driven a school bus with ESC and felt the impact it makes to prevent loss of control — especially when driving too fast on a curve.

The NTSB, which advocated for school buses to be included in NHTSA’s 2015 ESC rulemaking, is investigating the Chattanooga crash and will issue a final report in about a year. It will be interesting to see whether ESC enters into the agency’s analysis.

Meanwhile, we now know that NHTSA is taking another look at ESC for school buses, but it remains to be seen whether that will lead to a new rulemaking.

The bottom line is that while ESC doesn’t take any responsibility away from the driver, in some situations it can help the driver keep the vehicle under control.

Related Topics: electronic stability control, NHTSA, NTSB, school bus crash, Tennessee

Thomas McMahon Executive Editor
Comments ( 1 )
  • Bryan

     | about 11 months ago

    I also wonder how tempered vs. laminated glass, in the student windows, could be a factor in keeping students inside.

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