Vehicle Dynamics and Training

Joe Autera

THE BASICS
Vehicle Dynamics, two words you tend to see often in RFP’s, brochures, and on web sites dealing with driver training. Unfortunately most people don’t quite understand what the words mean and how it affects driving and driver training. As an example, we recently reviewed one of the many solicitations we receive for submitting bids on driver training programs. They asked the bidders to include a “vehicle dynamics exercises”.  Well, the simple fact is that driving to the shopping mall, parking your car, parallel parking are all exercises in vehicle dynamics. In fact, Vehicle Dynamics is not just one part of a training program it is the foundation of any driver training program.

While that may seem like a bold statement to some folks out there, the standard explanation of Vehicle Dynamics used by groups such as the Society of Automotive Engineers (SAE) demonstrates that this is fact, not just an opinion.

VEHICLE DYNAMICS
Vehicle Dynamics is the application of the laws of physics to a vehicle in motion.

That vehicle can be a fighter jet, train, or a horse draw cart. In our case it is a vehicle with four rubber tires or two or as in some training we have done 18 rubber tires. The basic principals are the same no matter how many tires are attached to the vehicles.  Hence when driving through cones, around corners, or trying not to hit a solid object the vehicle/driver combination must operate within the laws of physics. 

What is hard for most driver trainers to accept is that all driving scenarios, no matter how simple or complex, are an exercise in the laws of physics or, according to the SAE and others, vehicle dynamics.  Makes no difference if it’s a training program for high risk or low risk environments, or what type of vehicle – sedan, armored SUV, Lenco BearCat Tactical Vehicle or a bus, nor does it matter whether it’s a private sector corporation, government, military, or police agency. Because in both the training environment and the real world, the only set of laws we must live within while operating a vehicle are the laws of physics.  Luckily for us, the same laws apply equally to our adversary as well.  Which is why it is absolutely critical that any individual teaching advanced driver training have an understanding of the laws of physics associated with vehicle dynamics and, perhaps most importantly, be able to translate them into information that is useful to the student?

Having been at this for nearly four decades, it has become obvious that most people shy away from using the laws of physics as a training tool because of the math it requires. This may well be due to the fact that, for most people, their only exposure to the laws of physics is what they were taught in high school, where the subject  is mired in books and often times  seems to have no practical value. For those who are mathematically challenged, once the theory is explained in an easy to understand manner that applies to something they enjoy doing – like driving and driver training - and they learn how to turn a classroom discussion into a hands-on practical exercise based on a real world scenario, it is truly amazing how much sense all that math actually makes. Not to be redundant BUT all driving scenarios, no matter how simple or complex, are exercises in the laws of physics, so understanding and being able to apply the laws of physics isn’t something that is nice to know, it is a necessity.  Also if one wants to be able to develop training that will require students to develop the knowledge, skill and driving ability that will increase their survivability in the real world understanding the laws of physics is a must. This understanding is also the key to measuring an individual driver’s capability behind the wheel. Or put another way, it’s the only way to objectively measure their driving skill.

MEASURING DRIVING SKILL
First and foremost driver training is a science. If an instructor places a student in a scenario that defies the laws of physics they will fail, over and over again. A driver’s limit is dictated by the laws of physics (a science) as they apply to a specific vehicle and environment, like it or not, and despite what some might say, driving is a MEASURABLE SKILL. Many of the multi- discipline training programs, many of which include a driver train component, will objectively test every discipline EXCEPT driving, from our perspective this makes no sense at all and is a dis-service to the student. While it is true that measuring driving skill is a bit more complicated than measuring the students ability to shoot and hit the target – as evidenced by the “clang” of steel or the holes in the paper – or one’s ability to disarm a knife wielding attacker – as evidenced by the Red Knife lying on the mat and the attacker “tapping out” at the end of the drill. When looking at driving skills, there has been a great deal of research done, money spent and data collected that allows us to better understand  how drivers make decisions in emergencies and  how long it takes them to make the decisions that determine success or failure. The end result of all this research is the advancements that have been made in measuring driving skill and, therefore, survivability in an emergency scenario. For some inexplicable reason most of this vitally important information is largely ignored by the driver training community, with the exception of some of the high end racing schools. The appendix provided below, which describes just a fraction of the books and Technical Papers we (those of us instructing at TSVDI) read and, in turn, translate into information that will enhance the driver’s survivability, provides some insight into the information that is available. We encourage anyone interested in driver training to read through them.

The data in these books and papers highlight the criticality of accurately measuring and monitoring driver/vehicle characteristics and performance.  These measurements are essential to any and all advanced driver training programs that seek to improve the driver’s ability to recognize and effectively respond to behind-the-wheel emergencies without losing control of their vehicle. In situations that offer the driver limited maneuvering room and even less time, maintaining  control of a vehicle requires the driver to operate within a narrow range of speed (deceleration or acceleration) and steering inputs, the limits of which are defined by – you guessed it, the laws of physics . Once that is understood, it begins to make a whole lot of sense that all of the research available arrives at the same conclusion, in an accident or ambush the difference between success and failure is measured in tenths of seconds, and/or an increase or decrease in steering angle of a couple of degrees, and/or a speed differential of 2 MPH. With the difference between success and failure being so small, it is absurd to attempt to evaluate vehicle/driver performance just by observing the vehicle as it is driven through an exercise or scenario, or, worse yet, attempting to evaluate and coach from the passenger seat, where it is simply impossible to discern the dramatic effect a small variation in driver inputs is having on the vehicles outputs.  Scientifically and accurately measuring performance is really not that difficult – all it requires is a $200 on board computer, a radar gun, perhaps a stop watch, a working knowledge of the laws of physics and the single most important component of all, - an open mind – it’s a practice that is largely shunned by the driver training community.  In turn, exercises are often conducted for the sake of conducting them, with no real thought given to developing or refining specific skill sets or, for that matter, how the exercise may apply to real world scenarios the student is likely to encounter. At its worse, this can be wholly counter-productive as certain exercises may have no practical application to the environments and emergencies a student may have to confront while behind the wheel.

DESIGNING DRIVING EXERCISES
The purpose of  placing a student in a given exercise or scenario is to evoke a response from the driver/vehicle which introduces or reinforces specific skills or skill sets , and to afford an opportunity to coach the student on applying those skills and, of course, measure their baseline performance and quantify their improvement. None of this can be accomplished without understanding of vehicle dynamics. This understanding leads to questions that a professional driving instructor asks and can provide answers to:

• How far apart are the cones in the slalom?
• What is the width of the barrier in the lane change?
• What is the maximum capability of the vehicle, measured in G’s, in each exercise?
• What is the maximum rate of de-acceleration of the vehicle?
• At what speed does the student approach the vehicles maximum capability in each exercise (or scenario) that you place them in?

Why are the answers to these questions so important? Because if the instructor does not know the maximum capability of the vehicle and what conditions and/or limitations an exercise will impose on that vehicle, it is impossible to measure the capability of the driver. And if the instructor cannot determine what the driver was capable of at the beginning of their training and then compare that to what the student is capable of at the conclusion of their training, there is no way to determine if the training was effective; in fact, there is no way to establish and meet objective goals for the training.  Perhaps more importantly, without measuring the student’s capability there is simply no way for them to fully recognize what they can, and cannot, do behind the wheel.

Ultimately, you cannot separate vehicle dynamics from driver training; hence instructors MUST have a thorough understanding of vehicle dynamics and the ability to apply that knowledge to driver training.  Because once they have that understanding, they then have the ability to provide training that incorporates the three critical factors of survivability behind-the-wheel emergencies – the driver, the vehicle and the environment – into exercises that not only provide a mechanism for measuring the driver’s improvement, but also closely replicate the types of emergencies he or she is likely to face.

For an example of just how advantageous this understanding  can be to the instructor, we  just need to look  back at a an Instructor-level Vehicle Dynamics and Exercise Design program TSVDI conducted for a Federal Agency. When we passed out the calculators (standard issue for the vehicle dynamics savvy instructor), one of the students was looking at the calculator like a monkey might look at a watch – confused. It wasn’t long before he came up to Tony and expressed his displeasure that he would have to learn math to pass the course. He, like many others we have trained, pointed out that during his high school days; (with some it even extends into their college days) math was the bane of his existence. In a roundabout way he made the point that he was concerned that he would not pass the course because of the math. Tony’s answer was the same for him as it has been for scores of others with the same concern - hang in for a few days, and give it your best shot, while we give our best shot to teaching you the math.

Three days later, as we were on the track designing a training exercise to recreate a specific incident that involved their unique vehicles and the difference a new found knowledge of math and vehicle dynamics made was quite obvious. Tony had put together some guidelines for the students regarding the exercise design elements, and this same guy that had, just a couple of days before, been concerned about passing the course walks up to him and says “I don’t agree with the way you suggested we design this exercise”. He then proceeded to walk Tony through nearly a full page of calculations he had worked out to express how he thought the exercise should be designed and thoroughly explained why he thought that. In just a few days this instructor had gone from being intimidated by the math required to design driving exercises to combining his knowledge of the laws of physics (and, god forbid, math)  with his operational knowledge of the agencies mission objectives, the unique vehicles they operated and the types of incidents they had faced in the past to develop an exemplary driving exercise; one in which the drivers capability to resolve the problem while maintaining control of the vehicle was able to be objectively measured and, more importantly, drivers would be able to recognize that they were fully capable of resolving successfully.

At the end of the day, that is the real value provided by an instructor who understands vehicle dynamics and how they apply to drivers training.

Appendix One
Listed below are a small number of the Books and Papers that guide Scotti Certified Instructors

Books
The Fundamentals of Vehicle Dynamics
By – Thomas D. Gillespie

How to Make your Car Handle
By - Don Alexander

Driver Safety Systems
By – Bosch

Professional Driving Techniques
By – Anthony J Scotti

Road Vehicle Dynamics
By -  Dukkipatti – Pang – Qatu – Sheng – Shuguang

Race Car Vehicle Dynamics
By – Milken

Analysis Techniques for Racecar Data Acquisition
By – Haney

Society of Automotive Engineers Papers
Motor Vehicle Driver Characteristics – Crash Avoidance Behavior - SAE Technical Paper Series # - 2007 – 01 -1449

Evaluating Driver Response to a Sudden Emergency - SAE Technical Paper Series # -  2002 – 01 – 0089

Vehicle Handling Assessment Using a Combined Subjective – Objective Approach
SAE Technical Paper Series # - 980226

Driver Ability in Closed Circuit Testing -
SAE Technical Paper Series # - 2000 – 01 – 0179

ISO Lane Change Simulation - SAE Technical Paper Series # - 2002 -01-1569

What Constitutes Good Handling - SAE Technical Paper Series # - 2004 – 01 – 3532

Effects of Loading on Vehicle Handling - SAE Technical Paper Series # - 980228

Recent Trends in Van and Small Truck Safety (Old) -  SAE Technical Paper Series # -790478

Nighttime Driving and Visual Degradation (Old) -  SAE Technical Paper Series # - 820414