PoliceDriver.Com The gateway to a collection of educational information and resources for the driver trainer
An Introduction
About PoliceDriver.Com PoliceDriver.Com (PDC) is an information source for those with an interest in Vehicle Dynamics and its application to driving, vehicles and driver training. PDC is the gateway to a collection of educational information and resources for the driver trainer. The information is disseminated via Blog Posts, and eventually Powerpoints, and white papers. The goal of PDC is to share knowledge and to simplify the Science of Driving. We are opened, in fact welcome, others to submit articles for publication in PoliceDriver.Com. Editor - Tony Scotti For more than 40 years Tony Scotti has combined his knowledge of science, (He holds a B.S. in Engineering from Northeastern University) and Vehicle Dynamics to accommodate the training needs of corporations and public service agencies. He has conducted instructor level training programs for governments, corporations, law enforcement agencies and military. Going on his 5th decade his training programs have been conducted in over 33 countries, and he has trained students from sixty-four countries and conducted training programs on five continents. Co Editor - Dan Donza Dan is a retired Detective from the New York City Police Department; he joined the force in 1990. From 1997 until retiring in 2011, he was assigned to the Police Academy Driver Education & Training Unit as a classroom and field instructor. Dan taught emergency & non-emergency driving skills, safe vehicle operation, tactical vehicle tips & techniques, vehicle dynamics, and legal issues related to proper vehicle operation. As the lead driving instructor for the unit he developed curriculum, created, updated and revised lesson plans, conducted instructor development programs, and was the Commission on Accreditation for Law Enforcement Agencies Driver Training Coordinator. Dan possesses instructor certificates from the New York State Division of Criminal Justice Services in General Topics, Emergency Vehicle Operation, and Police Pursuit. He holds a Master EVOC Instructor certificate along with a National Driving Instructor Certificate from the Federal Law Enforcement Training Center. After retiring from the police department Dan joined the instructor staff of Tony Scotti’s Vehicle Dynamics Institute where he continues to teach advanced driver training topics including security / evasive driving programs, off road 4 wheel drive operation, high center of gravity vehicles, armored and SWAT vehicles. Dan is a member of ALERT International (The Association of Law Enforcement Emergency Response Trainers) since 2000 and it’s Northeast Regional Representative since 2008.
Line of Sight and Emergency Driving We have all had the experience of driving on a major highway and running into stop and go traffic, the first thought you have is that there must be an accident just over the hill or around the bend. But when you get to the top of the hill or around the bend the traffic starts to flow, and there is no accident – what caused the slowdown. Two things traffic volume and “line of sight." Line of Sight or Sight Distance is defined as the length of road surface a driver can see and have an acceptable reaction time. The people that are responsible for designing our highways, the American Association of State Highway and Transportation Officials (AASHTO), have guidelines concerning “line of sight”, and from those guidelines developed the all-important Decision Sight Distance (DSD) AASHTO defines DSD as the distance needed to recognize a problem and complete the maneuver safely and efficiently. And according to the scientists who have done an enormous amount of research on driver reaction time the “average” driver needs 2.5 seconds to complete the “recognize a problem” part of the DSD. The questions then becomes – How much distance do you use up before you get to the “maneuver safely and efficiently” part of the process. A good rule of thumb is that for every 10 MPH a driver needs 40 Feet of sight distance. If you are moving at highway speed of 60 MPH, you will need 240 Feet (40X6) of sight distance at 75 MPH you would need 300 Feet. Hence, if you are driving on the highway and for whatever reason, usually a hill, or a series of bends in the road, and there is not 240 to 300 feet of sight distance, drivers will slow down. If the volume of traffic is sufficient, it will cause an accordion affect. Please keep in mind that these distances are for the average driver Sight distance plays an important role in police driving. It is a major factor in determining if the event you drive into is winnable. During patrol know how far you can see NEVER DRIVE FASTER THAN YOU CAN SEE – Which means drive at a speed that will not give you the time to react at the given sight distance. The question you need to ask yourself is “At the speed I am moving with the given sight distance how much time do I have – and in that time frame what can I do with the vehicle.” It makes no difference what training you received and where you received it or what type of vehicle you are driving. No matter what the scenario If you don’t have enough sight distance at the speed you are moving it is a no win scenario.
In the Blink of An Eye Police Driving is a decision making process that requires the driver to manage time and distance, and anything that slows that process down can and often does become an emergency. Whether driving on routine patrol, pursuit or while off duty with your family understanding the basic principles of managing time and distance is life saving knowledge. Our frame of reference for measuring time and distance is the speedometer which supplies information in units of miles and hours – MPH. The driver does not have an hour or a mile to make life saving decisions; in a vehicle emergency Miles Per Hour is irrelevant unit of measurement. An Explanation To make sense of a vehicle emergency the driver needs to convert MPH to Feet Per. Second (FPS). Travelling at 40 MPH the driver is moving at the rate of 58.8 Feet Per Second (FPS). Converting MPH to FPS requires some elementary grade arithmetic; you need to multiply the MPH number by 1.47. Driving at 30 MPH the vehicle is moving through space at 44.1 Feet/Second,( 30 MPH times 1.47) at 60 MPH the vehicle is moving 88.2 Feet/Second ( 60 MPH times 1.47). Distance At 20 mph the driver travels 29.4 ft/sec At 30 mph the driver travels 44.1 ft/sec At 40 mph the driver travels 58.8 ft/sec At 50 mph the driver travels 78.5 ft/sec At 60 mph the driver travels 88.2 ft/sec As mentioned above any delay in the decision making process adds exponentially to level of difficulty needed to survive the event, not delays of measured in seconds but delays measured in tenths of seconds. As an exam-
ple; at 30 mph, in .2 seconds, the driver travels 8.8 feet, at 60 MPH in .2 seconds the driver would travel 17.6 feet. Why two tenths of a second? Because that is how much time it takes to blink your eyes. When you are driving 60 mph, literally in a blink of an eye, you move 17.6 feet. Any training that can speed up the decision making process – by as little as a blink of an eye dramatically increase the chances of surviving the emergency. MPH Distance Travelled In The Blink of an Eye 20 5.88 Ft 30 8.82 Ft 40 11.76 Ft 50 14.7 Ft 60 17.64 Ft
Emergency Maneuver vs. Pursuit Training to avoid an emergency is difficult for both the student to learn and the instructor to teach. When the officer is confronted with an emergency the amount of turning, steering and braking that is needed to get out of trouble is not predetermined, in fact that’s why it’s called an emergency. When the officer is confronted with an emergency – it’s “Holy Stuff”, and then the driver goes to work. From a vehicle dynamics perspective an emergency maneuver is different than driving through a corner. When driving through a corner the energy applied to the center of gravity of the vehicle is being applied relatively slowly and smoothly. I know it does not seem slow from inside the vehicle but from vehicle dynamics point – it is. There is a big difference between energy applied to the vehicle going through a corner at speed and the energy applied to a vehicle during an emergency maneuver. In an emergency, there is a huge spike of energy applied to the center of gravity of the vehicle. Again the officer does not purposely put a high spike of energy on the vehicle. Consider that if they are moving at the rate of 40 MPH and an obstacle is in their path 75 feet away they are 1.25 seconds away from the obstacle. Since it is a surprise, the driver’s reaction time will eat up at least half a second. At that point the driver has to apply enough energy to move the vehicle away from the obstacle and not too much energy that would cause the vehicle to go out of control, and do all that in a couple of tenths of a second, in the blink of an eye. The success of the event will depend on the speed of the vehicle, how quick the steering wheel is moved, and the capability of the student/vehicle combination. Racing fans may consider the following blasphemy. But when the center of gravity of a vehicle gets hit with a large spike of energy it does things that would challenge the best racer. The officer will need to perform an emergency maneuver with a vehicle that has about 75% less handling capability of the average race car. That is one hell of a dance. The skill needed to drive out of an emergency will not be learned driving lines and apexes. This is a skill learned in the lane change exercise –the dimensions of the exercise, the speed the students enter, and when the signal is given for the lane change all need to be synchronized. When it’s all together and working, it is one of the most valuable skills that can be taught.
Reaction Time
While driving if confronted with an emergency scenario, the driver’s reaction time can be the difference between success and failure. Although it is an important part of driving, and driver training reaction time is not easy to demonstrate. But there are exercises that can show the effect of reaction time on the decision-making process. The Reaction Time Process There are many factors that can affect the driver’s reaction time, but before we talk about them, let's find out just what reaction time is. Reaction time is the sum of the time needed for: 1. The brain to receive information from the senses. The senses we're referring to also include sensations of motion and related "seat of the pants" sensations. 2. Making decisions on what to do next. Many times, this is a reflexive reaction that carries a potential for danger with it, such as immediately smashing down on the brake pedal when we feel the car begin to skid. 3. Transmission of the messages from the brain to the muscles needed to react and move the controls. 4. The muscles to respond. Step 3 is important, but there is not much that can be done in an EVOC program to improve that portion of reaction time. The most-critical portion of the reaction process is Step #2. After the senses detect the danger, a decision has to be made about what to do with the received information. The time proven example of the inter action between steps 2 and 3 are young drivers. They have very fast reflexes, Step 3, but it is preceded by the wrong decision Step 2. They can react fast (Step 2) but unfortunately, they make the wrong decision, and they do it quickly. Surprise vs. Reaction Time The best research done on the affects of surprise on reaction time is by Dr. Marc Green. He has been studying the concept of reaction time for over 34 years. If you are running an EVOC program I would strongly suggest you read his work – just Google his name, and you will get many articles written by the Doctor. In one of his articles, he discusses the difference between reaction time when the event is expected, (which could relate to an experienced driver) and when the event is a surprise (that could relate to an inexperienced driver). As an example, when the driver knows they have to brake they can achieve the best possible reaction time. Dr Green says that the best estimate is 0.7 second. Of this, 0.5 is perception and 0.2 is movement, the time required to release the accelerator and to depress the brake pedal.
When the need to brake is a complete surprise reaction time is substantially different. In this case Dr. Green suggests that the best estimate is 1.5 seconds for something that may be coming at you from the side and a few tenths of a second faster for straightahead obstacles. Surprise creates a perception time of 1.2 seconds and a movement time of 0.3 second. The Numbers As many of the articles in the past have mentioned, an emergency is a time distance relationship. How much time does the drive have and how much distance does the driver have. If the decision-making process eats up a big chunk of time nothing good is going to happen. As an example - If the driver is moving at 40 MPH (58.8 Ft/Sec) and is driving into exercises where they expect to use the brake, the distance used up in reacting to the exercises would be .7 times 58.8 feet or 41.3 feet. Same speed the driver is surprised and then reacts at 40 MPH (58.8 FT/Sec) the distance used up would be 1.5 times 58.8 feet or 88.2 Ft. Demonstrating Reaction Time This is a learning point that does not add time to your training program yet can be an invaluable tool. An exercise you find in most all EVOC programs is the Slalom course. Cones separated by a known distance and the student drives through them at a speed the instructor determines. I’ll use the dimension of the slalom course we use at our training program which is cones separated by 60 Feet. Students start out an around 30 MPH; speed monitored by a radar gun. 30 MPH is approximately 44.1 Feet per Second; the cones are 60 Feet apart if you divide 60 by 44.1 you will find that it takes 1.36 seconds to drive from cone to cone. That
would be 1.36 seconds for the student to make all the decisions they need to make, so they don’t hit the next cone. Raise the speed to 35, which is 51.45 Feet per Second follow the same math divide 60 by 51.45 and the student now has 1.16 seconds of decision time between cones. An increase in 5 MPH and a decrease in time to react (reaction time) of .2 seconds, ask your students the difference that .2 seconds less time to react makes, I’m sure the answer will be a lot. At 40 MPH that would be 58.8 feet per second same math would give you 1.02 seconds in between each cone. At 40 MPH with cones at 60 Feet, it would be extremely difficult, if not impossible. The difference between it being easy and be being near impossible is .3 seconds. If you’re going to do this it has to be done using a radar gun, you cannot accurately measure speeds by sitting in the passenger seat looking at the speedometer. Lesson Learned As little as .2 seconds more time to react makes the difference between success and failure. By the way .2 seconds is the time it takes to blink your eye. In the blink of an eye, you can change failure into success.
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