198 – Tires and Tire Pressures, Dynamic and Human Driving Tasks

For this week’s episode we are revisiting a previous topic, tires and tire pressures, to answer a question we received, and we’ll introduce a new paradigm – the Dynamic Driving and the Human Driving Tasks. 

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Tires and Tire Pressures

The reason we spend a lot of time talking about these subjects can be found in a comment made by a Bridgestone engineer – “Tire pressure affects every aspect of the tire, including the load-carrying capacity, tread contact patch shape—where the tire touches the road—and size and handling characteristics.” 

Therefore optimizing tire pressure will increase the safety and security of the principal and is essential knowledge for the Security Driver and Executive Protection Practitioner.

As we have often said, tires are the only part of your vehicle that makes constant contact with the pavement. 

To obtain the vehicle manufacturer’s suggested inflation level for your executive vehicle, take a look at the tire sidewall and the label often located in the door jamb. If it’s not there, check the owner’s manual. 

Recently, we were asked why tire sidewalls often show a pressure rating, shown in maximum pounds per square inch (psi), that differs from the vehicle maker’s recommendation.

How is the recommended tire pressure determined?

How do they determine the recommended pressure that appears on the tire and the recommended pressure on the sticker located on the vehicle or in the vehicles’ manual?

To get the answer, we did go to the standards set by the Tire and Rim Association (TRA) in the United States and the European Tire and Rim Technical Organization (ETRTO). We looked at their guidelines in developing tire sizes’ maximum psi and maximum load levels.

The maximum tire pressure is precisely that the maximum pressure the tire can safely hold. But within that, there is the ideal pressure to maximize the performance of the vehicle, and that is the tire pressure recommended by the vehicle manufacturer. 

Tire manufacturers develop ideal tire pressures based on various factors such as how much load the vehicle puts on its left front wheel during a right turn at 60 mph. 

We assume that the tire manufacturer drives the vehicle at the maximum handling capability of the vehicle tire combination at a speed of 60 MPH. This is our assumption, and it seems to make sense.

Through rigorous testing, the vehicle’s recommended tire pressure is determined, with the idea of balancing considerations of performance, fuel efficiency, safety, and overall longevity.

Check PSI Once a Week

The key to maintaining proper tire pressure is checking psi levels at least once a week or more. But according to the tire companies and the National Highway Traffic Safety Administration (NHTSA), not many people do that. Just 19 percent of drivers properly check and inflate their tires, even though tires tend to deflate by about one psi a month. According to the agency, about a quarter of all cars have at least one tire that is significantly underinflated. As a Security Driver or Executive Protection Practitioner that can’t be you.

Tire Pressure Monitoring System

At some point, almost everyone has seen the tire pressure monitoring system (TPMS) warning light appear on the dashboard. Its purpose is to warn you that at least one or more tires are significantly under-inflated, possibly creating unsafe driving conditions. The tire pressure readings are provided by pressure-sensing transmitters mounted inside each tire and sent to a central computer (ECU) for display on the dashboard. The problem is that the warning light on the instrument panel does not come on until there is a 25-percent drop in tire pressure. By the time the warning light is displayed, you and the passengers are in a very unsafe vehicle.

If you have attended a protective driver training program, you should know how much tire pressure affects a vehicle’s ability to corner, drive out of an emergency, and stop.  A while back, we produced an episode on TPMS, and we mentioned that by the time the TPMS light comes on, the driver would lose 15 to 20 percent of the vehicle’s emergency capability. That means if the vehicle/driver combination could escape an emergency at 40 MPH, they could not avoid the same scenario at 32 MPH if the TPMS light is on. 

The Dynamic Driving Task and the Human Driving Task 

In all our 48 years in the profession, we would have never thought or considered that the automotive engineering community would be required to define how humans and computers interact while driving a vehicle.  A human interacting with the vehicle computers, specifically the ADAS, is called the human driving task.

Before we talk about the Human Driving Task, we need to talk about The Dynamic Driving Task, which may sound familiar to old Scotti School and present VDI students – it is the Security Driver Triangle – driver, vehicle, and environment. 

Dynamic Driving Task

Similarly, the Dynamic Driving Task is defined as – the driver performing the lateral and the longitudinal driving task by considering the driving environment. 

The Society of Automotive Engineers (SAE) defines the environment as – road markings, road signs, road infrastructure, other vehicles, objects on the road/roadside, other traffic members. The Security Driver must monitor all of the previously mentioned, not only in the mode of safety but also include their security implications.

The SAE has a standard for the definition of Monitoring the Environment. According to the SAE Standard J3016, Monitoring the Environment is defined as all the activities and/or automated routines that accomplish comprehensive object and event detection, recognition, classification, and response preparation, as needed to perform the dynamic driving task competently. The key phrase is “or automated routines.” Vehicles equipped with ADAS are monitoring the environment for safety, not security.

When driving vehicles that are not equipped with automated driving systems, human drivers visually sample the road scene sufficiently to competently perform the dynamic driving task while also performing secondary tasks that require short periods of eyes-off-road time (e.g., adjusting cabin comfort settings, scanning road signs, tuning a radio, etc.). Thus, Monitoring does not entail constant eyes-on-road time by the human driver

We know that there are times when the Security Driver will need to take their eyes off the road, but that has to be kept as short as possible.

The Human Driving Task

The Human Driving Task is defined as a person who drives a particular vehicle and who, in a vehicle equipped with an automated driving system, exchanges the dynamic driving task with such a system as necessary during vehicle operation. 

What that means is if the ADAS has detected what it feels is a problem, the Human Driver “exchanges,” which means hands over control to the ADAS.

Once the ADAS takes over the Dynamics Driving Task, it supplies what the SAE calls a  REQUEST TO INTERVENE. This is a notification by the automated driving system to a human driver that s/he should promptly begin or resume performance of the dynamic driving task

In our opinion, the SAE Standard J3016 and the Human Driving Task were brought on by the introduction of the various levels of autonomous driving, and the ISDA feels these ads posted by many of the vehicle manufacturers are irresponsible. 

Human Driving and Dynamic Driving tasks in relation to autonomous driving

Let’s talk about Human Driving and Dynamic Driving tasks in relation to autonomous driving.

Autonomous LEVEL 0 – NO AUTOMATION – The full-time performance by the human driver of all aspects of the dynamic driving task. There are not many Executive Vehicles that have no ADAS.  

LEVEL 1 – DRIVER ASSISTANCE – The part-time or driving mode-dependent execution by a driver assistance system of either steering or acceleration/deceleration with the expectation that the human driver performs all other aspects of the dynamic driving task. All Executive Vehicles are Level 1. The Security Driver needs to know and understand what portion of the dynamic driving task the ADAS is monitoring; it may not be the same task when moving from one vehicle to another.

LEVEL 2 – PARTIAL AUTOMATION – The part-time or driving mode-dependent execution by one or more driver assistance systems of both steering and acceleration/deceleration with the expectation that the human driver performs all other aspects of the dynamic driving task. Most all Executive Vehicles are Level 2. It is the same scenario as previously mentioned. The Security Driver needs to know and understand what portions of the dynamic driving task the ADAS is monitoring; it may not be the same task when moving from one vehicle to another.

LEVEL 3 – CONDITIONAL AUTOMATION – The part-time or driving mode-dependent performance by an automated driving system of all aspects of the dynamic driving task with the expectation that the human driver will respond appropriately to a request to intervene. Some but not all Executive Vehicles are Level 3.

In a past episode – episode 152, we talked about the Security Driver Algorithm. We covered what the SAE calls Intervene, but others call it the switch point. As we mentioned, the point where the ADAS (aka the computer) asks the driver to “intervene” may work well in a safety scenario but not in a security scenario. 

Here is the excerpt from episode 152.

The Switch – Security Versus Safety 

When the ADAS takes over control of the vehicle, it’s not making decisions based on security; the computer makes decisions based on what an algorithm says the vehicle’s path should be. In a security scenario, the path the computer wants you to drive and the path the driver will need to avoid a security incident may not be the same. The vehicle can supply the safety algorithm – but the driver’s mind and eye working with their skill, knowledge, and experience are the security algorithm. 

The question that the ADAS algorithm cannot answer is the switch due to safety or a security event. The algorithm can’t make that decision. The individual holding on to the steering wheel has to control the security algorithm.

The Switch Point and Training

The switch point, the switch from a human to a computer controlling the vehicle, is becoming a science all unto itself. From the training perspective, this change from human to computer needs to be managed; training scenarios need to be designed to create the switch, and instructors need to know how to measure the driver’s response to the switch. 

It is imperative that the instructor knows when, where in the exercise, and at what speed the switch will occur before the driver enters the exercise. The switch needs to be monitored, instructed, measured, and made into a teaching point.

As a security driver or supplier of secure transportation, your job is to drive the vehicle and perform the dynamic driving task in safety and security.

Keep in mind that when driving a vehicle equipped with ADAS, understand that you have switched from the dynamic driving task to being part of the human driving task. It is your job, your obligation to understand the switch from you controlling the vehicle to the ADAS controlling vehicle.

If you attend either Executive Protection or protective driver training program, the switch from human to computer control of a vehicle needs to be discussed.

Join ISDA

If you have an interest in going much deeper into these types of topics, I invite you to check out the International Security Driver Association’s website and consider joining the membership to gain access to the encyclopedia of executive protection and secure transportation – The ISDA Knowledge Center.

For more information on all of the member benefits head over to https://isdacenter.org.

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