Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the practical application of health information. Nutrition. Exercise. Diet. Supplementation. I look at the science behind them, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
Has this ever happened to you? I was waiting behind someone at a red blinking left turn signal. You know the kind—stop and then go? The traffic was clear, but the driver decided to wait. When it turned to a green arrow, off they went. A little later, I was in the same situation but behind a long line of cars. This time, it seemed to take forever before the first car moved, then the second car, and on and on. I’ve said, “What are they waiting for, a written invitation?” that my grandson Riley is starting to pick it up. Who knows what they were doing to take so long to respond. There is a possibility, though.
There is little question what’s going on since the last time I approached this subject with the volume of smart phones that are available today: the people were texting. A clue was that their heads were looking down. Aside from the fact that it’s illegal here in the state of Michigan, and probably where you live as well, it creates a whole set of problems. While that’s bad but just irritating, the real problem exists when people text while driving. I’ve seen a person holding their phone in the center of the steering wheel so that their fingers were free yet make it seem like they actually were steering the car. In a parking lot recently, a woman was texting as she passed me and driving into a parking place. What in the world is so important that you can’t wait just three seconds?
There are so many issues texting causes, such as decreased attention, but to me, the real issue is reaction time. That’s the time from the onset of a stimulus until the movement is completed. In this case, the stimulus is the appearance of the arrow and pressing on the gas pedal that’s starts the car moving is the completion of the movement. But if someone isn’t looking at the arrow to begin with, the process never begins. It’s even worse when someone is in a moving vehicle. Let me give you a couple of examples so that if you text and drive, you may decide to stop.
There are different speed limits for cars and big rigs on the highways. As a result, when a truck passes a truck, a line of cars that want to pass both trucks piles up behind the truck in the passing lane. What amazes me is how close cars will get to the cars waiting to pass—sometimes less than a car length— as they line up to pass the trucks.
If you’re traveling at 70 mph, you’re going 102 feet per second—roughly 33 yards as we’re in football season as I record this. The average car is 12 to 18 feet long. That means if your reaction time from floor to brake is a tenth of a second, you will just miss hitting the car in front of you IF you’re about one car length behind. That’s if they just tap their brakes; if they brake to stop, no way you’re going to miss them. And that wouldn’t be very good for your health.
Keep in mind that reaction time declines as we get older. Combine that with not being as fit and muscles not being as toned, and driving too close could end up being a disaster.
Now let’s get to a texting and driving scenario. Let’s use 20 mph as the speed a person is traveling. That’s the typical neighborhood speed of 20 mph—at least here in Grand Rapids. Kids out playing and kicking a ball into a street. People riding bicycles. 20 mph works out to about 30 feet per second or about 2-2.5 car lengths depending on the car. These are the factors that have to be considered according to the Safety Center at Southern Illinois University. They’ve broken stopping while driving into four different categories.
Human Perception time/distance is the distance your vehicle travels from the time your eyes see a hazard until your brain recognizes it. Perception time for an alert driver is about ¾ second—a lot longer than I used in my example at highway speeds. At 55 mph, a car would traveled 60 feet in ¾ second. If a driver is distracted by texting, the process would start when they see what’s in the road in front of them be it someone crossing an intersection or a car that put on their brake lights. At 20 mph, the car would travel about 23 feet or one and a half car lengths in that time—and we haven’t started to brake yet.
Keep in mind that it’s even more complicated than this. One hand is off the steering wheel while a person is texting—unless someone is steering with their knees—which I have seen happen when someone is eating and driving. Having one hand on the wheel means that a person would most likely turn the wheel toward the hand that’s on the wheel—right if the right hand, left if the left hand.
Human Reaction time/distance is the distance traveled from the time your brain tells your foot to move from the accelerator until the time your foot pushes the brake pedal. An average driver reacts within ¾ second. So, we’re adding another 1.5 car lengths if we’re traveling at 20 mph or another 23 feet.
Vehicle Reaction time/distance. Once the brake pedal is applied there is the vehicles reaction time. That’s the time it takes the braking system starts to actually engage the brakes. That depends on your car and it can be anywhere from immediately up to 1/4 second. That could be one-half car length at 20 mph or about 10 feet.
Vehicle Braking distance is the distance it takes the vehicle to stop once you hit the brakes. That has about 10 variables to consider from the type of braking system, tire pressure, and status of the pavement. Dry, wet, or ice-covered in which case the person driving is toast. At 20 mph on dry pavement, it would take a car with good brakes about 1.5-2.0 seconds to stop. That’s adding another 3-4 car lengths or 45-60 feet to stop.
When you consider all factors, it would take 3-4 seconds to stop and the car would travel 55-70 feet under ideal conditions—and you’re only going 20 mph. When’s the last time you really drove that slow in neighborhood traffic? The real issue is that none of this time or distance starts until you actually see the problem. Even if you trained yourself to look up every second while texting, you’re going to add at least 20 feet to the calculations.
If you think this is complicated, you can break it down even further if we consider what’s going on with the eyes, nervous system, and muscular system.
I’ll confess that I tried stopping while doing 20 mph and it didn’t seem like it would take anywhere near the calculated distance for Vehicle Braking. What I could not duplicate was the Human Perception and Reaction times. No matter how real you try to make it, you react differently when you know it’s coming. The whole point is that when you’re driving, you don’t know it’s coming.
Can you improve reaction time? Yes—at least the neuro-muscular side. But let’s face it, between aerobic exercise and weight training, you’ve got enough to do to stay fit and healthy without adding more. The nice thing is that those activities do help the nervous system and muscular elements of reaction time as well.
But training reaction time to be able to text and drive is not the point. I would rather you eliminate texting while driving. Listen to another episode of Straight Talk On Health because for sure, I’m not going to put you to sleep. Focus on the task at hand and leave the texting to another time. I’d prefer for you get to where you’re going safe and sound. That’s it for this episode. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
