There are two words that are often used in the automotive industry and protective driver training vernacular the words are handling and cornering.
To get a better understanding of how the driver interacts with the vehicle requires understanding the difference between Handling and Cornering. While conducting a driver training program understanding this interaction is a must – when running a secure transportation operation, knowledge of this interaction adds to the principal’s safety and security.
Handling and Cornering are often used to describe the same vehicle/driver characteristics, but they are two separate issues.
Cornering is the amount of centrifugal force the car can generate measured in g’s, and is expressed as Lateral Acceleration, and can be called Cornering Power.
Handling can be qualified and quantified as to how the car responds to the drivers inputs – handling expresses controllability. It can be used to measure how much of the vehicle’s cornering power the driver can control.
Cornering and Training
Knowing how much cornering power is available for a vehicle has always been problematic – with some searching, you can find vehicles cornering power and numbers by looking at the test conducted by various car magazines – although they seldom test vehicles used in executive transportation.
But we did find that in a Motor Trend test of an S Class Mercedes-Benz, they measured the vehicle to have .88 G’s of Lateral Acceleration or Cornering Power. A Car and Driver test of the Suburban and the Exhibition measured them to have .68 G’s of Lateral Acceleration or Cornering Power.
As we have mentioned many times in the past, research and science define driving skill as the driver’s “ability” to use the vehicle’s “capability.”
The cornering power defines the vehicle’s capability, and the driver’s level of skill is determined by how much of that cornering power they can handle.
Cornering power is measured in Gs, which is a measurement of the amount of force exerted on the vehicle’s center of gravity. The higher the Gs, the more force the vehicle can absorb, which means there is more cornering power available to the driver to use in the event of an emergency.
Most magazines get their cornering power number via a Skid Pad, which is driving in a circle with a known radius and increasing the speed until they cannot keep the car on the radius, and then they take the MPH number and apply it to a relatively simple equation that determines the vehicles cornering power – lateral acceleration.
Although a skidpad is a good measurement of vehicle handling, security drivers don’t drive in circles all day. In an emergency, there is a substantial difference between the numbers presented via skidpad versus the numbers presented by an exercise such as the Lane Change. To ensure accurate cornering power numbers via skidpad or Lane Change requires the vehicle to be fitted with an onboard computer that measures the amount of GS the vehicle generates.
To ensure accurate results, the magazine’s instrument cars with computers that measure Lateral Acceleration/Cornering Power. The instrumentation used by car magazines tends to be expensive, but for very little money, $170, you can get an accurate G Meter device to measure the vehicle’s Lateral Acceleration/Cornering Power. Or, for 99 cents, you can download a G Meter to your Smart Phone, and you can apply a simple equation (5th-grade math required) to a slalom exercise and get accurate results. We use all three methods and compare the results.
When conducting a security driver program, you cannot measure the driver’s ability unless you know the vehicle’s cornering power. There is no excuse for not knowing a vehicle’s cornering power.
Handling is defined as how the car responds to the driver; handling expresses controllability. Handling is the car and driver working together. In an article that appeared in the publication Car Driver, engineers from several vehicle manufacturers said this about the definition of handling.
- Handling is about predictability – The car has to be stable up to the limit of adhesion.
- Handling is what happens when it reaches the limit of adhesion.
- When the car starts to lose its grip – the traction should not decrease quickly (like not fall off the end of a cliff) and should not create a surprise to the driver.
The engineers are all saying the same thing – what happens to the vehicle’s output at or approaching the limit of its cornering power is what defines handling.
Handling is communication between the driver and the car –good handling cars are linear. Good handling cars communicate the approach to the limit of adhesion – good drivers understand this communication – good driving instructors teach and coach their student to understand the communication between the vehicle and the driver, and scientifically measure the student’s capability.
Training and Cornering
A driving instructor should know the Lateral Acceleration/Cornering Power of the training vehicles, measured in G’s. If the instructor does not know what the vehicle is capable of – how would they know what the driver is capable of?
If the course has a slalom – evasive exercises – lines and apexes – high-speed driving, for example, and the instructor does not know the vehicles cornering power capability, or worse, does not know what lateral acceleration or cornering power is, and how to measure them, any critiquing by the instructor relative to those exercises is a guess and not even an educated guess.
Handling and Two Vehicle Scenarios – In the surveys for executive vehicles that we conduct every two years and have been conducting for the past eight years, the two vehicles that always come out on top as the most used are the Mercedes-Benz S class and the Chevy Suburban as an SUV – in the first part of the article we mentioned that the S class has a cornering power of .88 G’s In the Suburban has a cornering power of .68 GS.
As mentioned above, the cornering power of vehicles used in secure transportation vary considerably from a Mercedes-Benz to a suburban with high CG issue SUV, a Mercedes sprinter van to an armored vehicle; the cornering power of those vehicles changes dramatically As much as 33 to 35% from one vehicle to another.
Consider this if a Mercedes-Benz is used as the principal vehicle and a Suburban is used as a backup vehicle, the cornering power of those two vehicles can vary as much as 35 to 40%; the drivers of the two vehicles must manage the cornering power of the two different vehicles and to do so, they must be in sync with each other.
Protective driver training providers must have some form of a driving test to determine the vehicle’s cornering capability; for decades we use an adaptation of the ISO 3888 – 2 test. If the vehicle’s cornering capability is unknown, it is impossible to measure the driver’s ability to handle the cornering power that the vehicle presents.
As an instructor, understanding the difference between Cornering and Handling and the basics of Vehicle Dynamics is crucial in presenting a quality training program.
If you have an interest in learning more on these topics I invite you to check out the International Security Driver Association’s website ISDACenter.Org and get access to the encyclopedia of executive protection and secure transportation – The ISDA knowledge center. The knowledge shared encompasses a wide range of EP and ST focused topics with resources, information, and metrics.
For more information on all of the member benefits, head over to https://isdacenter.org.