Episode 158 – Measuring Driver Skill Level

This week, the topic is measuring a driver’s skill level.

Meeting the Demand

Starting in the mid-’70s, the Scotti School and now VDI clients wanted, actually demanded, that we supply them with an objective measurement of their employee’s driving skill, to produce a professional security driver who has been scientifically measured to an objective and documented standard. 

To meet that demand, we studied the research conducted by the Society of Automotive EngineersISO, and NHTSA. Back in the 1970s, conducting research was not as easy as it is now. There was no Internet and Google. 

Their research created an understanding of how drivers make decisions in emergencies and how long it takes them to make those decisions. We found that these organizations created minimum standards, based on the laws of physics, for measuring driving skill and, therefore, survivability in an emergency scenario. Also, we decided that to perform the duties of a professional security driver; the minimum standards were not sufficient.

80% Standard

From studying their research, we found white papers and studies that indicated that the average driver, when confronted with an emergency, can only use 40% of the vehicle’s capability before they relinquish control of the vehicle (give up). 

Starting in 1976, the Scotti School spent a considerable amount of time, effort, and money to develop training programs (Executive Protection and Security Driving) that implemented the standards created by these institutions. Please keep in mind that this was before computers. 

Our on-track testing showed that at the 40% mark, the vehicle becomes non-linear, which in turn creates driver anxiety (fear). We also found that once the driver was at the 40% usage of the vehicle, much more vehicle capacity was available for the driver to use. After a considerable amount of testing and evaluating, we decided that a good driver should be able to use a minimum of 80% of the vehicle’s capability, in the three modes of vehicle operation, in a measured minimum amount of time and space, to be considered for employment as the CEO’s driver—hence the 80% standard. 

The 80% standard has withstood the test of time. Forty-five years ago, the goal was to create a standard and training system accepted by the K&R and Corporate community, and that was accomplished. Anyone who attended an old Scotti School or a Vehicle Dynamics Institute program knows that reaching the 80% standard is demanding. 

How much of the vehicle do you use when driving the principal? 

During normal driving in any environment, you use 25% to 30% of the vehicle’s capability.

A while back, we (ISDA) conducted an experiment. Using a G meter in an iPhone App, we drove around in an urban environment. What is interesting was how little of the braking and cornering capacity of the vehicle is used during the daily driving routine. We measured .3 G’s braking and the highest G’s recorded topped off at .35 G’s while cornering. 

This was the normal braking you would do driving up to a stop sign or light. The cornering number only got to the .35 G range when I pushed it going around a rotary. Other than that, it was below .25 G’s. Society of Automotive Engineers paper has indicated that this is the comfort zone for most drivers. The vehicle we were driving had a capability of .85 G’s, which means we were using about 40% of the vehicle. 

But if an emergency popped up, a driver would instantaneously have to use .8 to .9 G’s, braking or cornering in a heartbeat. That’s what training is about, to get people past their comfort zones.

Translating the Numbers

Expressing skill levels in numbers is OK, but how do these numbers translate to reality? What is the driver experiencing at each of these levels of skill? 

Using 60% of the vehicle’s capability: 

If the driver uses 60% of the vehicle’s capability, they will start to feel changes in the vehicle’s feedback. The vehicle body will begin to lean. It will require constant attention, you can probably carry on a conversation, but you have to be paying attention to the road and keeping your eyes focused on what’s in front of you. Handling characteristics of the vehicle become evident. If the vehicle under or oversteers, you will start to feel it. If you are average or above average driver, you can control the forces acting on the car; driving at 60% is actually fun.

Using 70% of the vehicle capability: 

Your attention needs to be very high. If you are an above-average driver, the fun factor has gone up. The fun factor may be increasing for you, but the fun factor is definitely decreasing for your passengers; if they are not using seatbelts, they will start to move around in the vehicle. Objects in the car that are not tied down will also begin to move.

Using 80% of the vehicle capability: 

This will be a speed at which you cannot afford any superfluous conversation. 80% and above requires complete attention to the driving task. This is difficult and requires skill that comes from training; you are above average if you can accomplish this. You need to be ready for bad things to happen. Those handling characteristics that became evident at 60% will be slapping you in the face. You will have to use every bit of your skill to maintain control. Unless you are experienced at using this much of the vehicle, the fun factor is decreasing at a rapid rate. Passengers not belted in will start to be tossed around the vehicle, loose objects will become missiles, and the passengers will start to question your sanity.

90% of the vehicle capability: 

This will be too fast for anyone but a trained driver with a lot of experience. Small movements of the controls will create a loss of control. By this time, fun is not the operative word. Even if the passengers are belted in, the force will be so high that they will have a hard time moving their hands and arms. Small amounts of debris or imperfections in the road surface become real hazards. The question the passengers had about your sanity has been answered.

 100% of the vehicle capability:   

This would be driving at a speed that allows for no error and no unknown irregularity in the course or conditions. The vehicle will more than likely be sliding sideways. What you were looking at through your windshield will now appear in one of the front door windows. If sanity is intact, apprehension is present. Requires a great deal of skill and some luck; this is reserved for closed-course race car driving, such as qualifying for competition with the pole position in mind.


If you are attending a driver training program, the percentage of the vehicle you can use must be measured in all exercises. If not – why are you there? As an example, to pass a VDI protective driver training program, a student must achieve 80 % of the vehicle’s capability. 

 Although it is not recommended that you use 100% of the vehicle on purpose, but there will come a scenario where you will be required to use all the car has to offer in a very short period of time and space. 

 All the Above Can Be Scientifically Measured

There is equipment available now that can be plugged into the vehicle’s 12-volt power outlet to measure the amount of force the driver is applying to the vehicle. Depending on the device’s level of sophistication, it can be inexpensive ($190) or somewhat expensive ($1200). The device measures the force (G’s) exerted on the vehicle and how long those forces are applied. The measurement tells the instructor how much of the vehicle the driver is using. The high-end devices will transmit the results to your computer outside the vehicle. All the results are downloadable.

For the U.S. listeners – have a great Thanksgiving!

“Enjoy the little things, for one day you may look back and realize they were the big things.”

by Robert Brault

If you’ve enjoyed this week’s podcast episode, we invite you to check out the International Security Driver Association.  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.

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