Article,Features,Hypermiling

Pulse and Glide

17 Jul , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

In this post, I will attempt to provide a simplistic overview of a hypermiling technique known as “Pulse and Glide” (P&G). Before we get started, you need to know that the application and technique for P&G is variable based on many factors such as the car, terrain, traffic, current speed limit, etc. For all those reasons, this will be an overview and not overly detailed. My concern is that if I provided any real details: 1) you would try to apply the details where they don’t fit, and 2) someone will argue the minutia of the details.

How Do You Pulse and Glide?

Many times, I compare hypermiling to riding a bicycle. This works because almost everyone knows how to ride a bike, which makes it a universal reference. Also, you most likely remember how tired you can become if you do not ride efficiently. Though neither you nor your car will get tired, you have to focus on the amount of effort being exerted; the goal is to travel farther with less effort.

The Pulse. Just like riding a bike, the intent of the pulse is to get up to speed. When accelerating from a dead stop, use a brisk acceleration: accelerate quickly but not stomp on the gas. Once you have reached a speed that is, perhaps, a little faster than the speed limit or average traffic speed, let up on the accelerator.

The Glide. Think about riding that bike. Once you have reached a decent speed, it requires only a minimal amount of effort to maintain it. In fact, depending on the situation, you might be able to coast for a long distance before needing to pedal again. In exactly the same way, the point of the glide is to “stop pedaling”.

The first and second generation Prius were exceptionally good at gliding because they had a “dead band”. This dead band is a spot in which there would be no power coming from the engine or batteries to drive the wheels and also no regeneration from the wheels to the batteries. A practiced driver could work the accelerator into that dead band and let the car roll.

Unfortunately, this type of “free wheeling” is nearly impossible in almost all modern hybrids. And so it is with modern hybrids that the glide is an attempt to reduce the energy flow to a point as low as possible.

Pulse Again. As you can imagine, after coasting for a while, you will start to slow down. Once you’ve slowed to a speed you are no longer comfortable with, pulse again. Unlike the dead-stop pulse, this time you want to use just enough acceleration to get back up to speed. Just like riding that bike, it’s not a sprint back up to speed but rather just enough.

And then you glide again. Then pulse, then glide, repeat.

Why Does it Work?

The concept is simple: the entire intent of P&G is to glide more than you pulse. The following image provides a sort-of representation starting from a dead stop, accelerating up slightly above the desired speed, gliding, pulsing, and then gliding again. As you can imagine, the farther you can glide the better. The black line in the following image might represent the average traffic flow, the speed limit, or simply the speed you want to average. Your situations will vary.

Pulse and Glide Image

It works because gliding is essentially free. It’s the pulsing that costs you. Therefore, rather than paying to constantly maintain a steady speed, you allow your speed to vary. The trick comes in making sure the pulsing uses less effort than would otherwise be used maintaining a steady speed.

Situational Considerations

  • As with all hypermiling techniques, obey all posted traffic signs and do not impede the flow of traffic for your selfish desires.
  • If you have rolling hills, that is awesome. Pulse up the hill and glide down the other side. They key is being able to gauge the most efficient time to transition from pulse to glide and vice versa.
  • One hypermiler told the funny story of being pulled over because the policemen observed he was “incapable of maintaining a steady speed” and assumed he was drunk. I didn’t say it was funny for him. He said that once he explained what he was doing, the policemen didn’t bother writing a ticket.
  • If you see a stoplight up ahead, consider modifying your pulse and glide timings to either glide into the stop or pulse a little faster to ensure catching the green light.

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What Drives Us episode

Read the Stoplights

4 Jun , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

There is no denying that one of the greatest hindrances to hypermiling is the stoplight. They force you to ruin a perfectly good head of steam and then force you to make the car accelerate from a dead stop. As mentioned in another article, it would be best to use the brakes as little as possible by timing the stoplights such that stopping is not required. Some suggestions were provided in that article but they only scratched the surface. This article aims to dig deeper and provide some suggestions and insight into dealing with various types of stoplight intersections.

NOTE: These examples are based on my experience with stoplights. There are some places were the order of progression is different from those given below. For example, in some locations, left-turn lights precede straight whereas in other places, straight precedes turns. If the lights are different where you live, then please try to work out the differences as they apply.

The Standard Stoplight

Let’s start with an easy one.
1. Easy Stoplight

In this case, the stoplight is green and you can continue through it. But is it really that easy? How long has the light been green? If you know your route, you have a general idea how long before this light changes to yellow and then red.

If you just saw this light turn green, take your time. However, if you feel this light is “stale” or have no idea when it might change, then it might be best to accelerate through it. Sometimes it is better to burn a little gasoline speeding through a light than take the massive hit brought on by dead-stop acceleration.

Red Means Stop

Here is a typical red light.

2. Red LIghts - Yellow on the Sides

Most people would look at this and see that the light is red and therefore, you will be required to stop. A hypermiler, on the other hand, looks at the side lights and sees they are yellow. With some luck and good timing, you should be able to coast up to the light just after it turns green. Always watch the side street for people running the yellow or red.

Bonus Points: If you are turning left at this intersection, you are most likely going to stop. Many left turn lanes are triggered only when there is a car waiting. Since this scene does not show a car, there is a good chance the “straight” light will change green while the left-turn light will stay red. If you have the option, consider continuing straight and trying your luck with the next light.

Left Turn Light

Notice that the left turn light is green and there is a car waiting to go straight.

3. Green Lights with Green Turn Light

If you are going straight through the intersection, there is no need to rush. The left-turn light is delaying the oncoming traffic. Even after the left-turn light changes to yellow and red, the oncoming traffic will have their entire turn during which time you will have the green light.

This is also important when there is a line of cars in front of you. Perhaps only ten cars can get through the light normally; when the left-turn light extends the straight light, perhaps fifteen or twenty.

Car Turning Left

Notice that the oncoming car is going straight while the car in front of you is turning left.

5. Red Lights - Car Turning Left

In a very real way, this situation is about ten seconds prior to the previous image. The car in front of you will trigger the left-turn light when your light turns green. The oncoming car is not in the left-turn lane and will sit there. You will have an extended green light to proceed at whatever rate you desire.

Red Light with an Oncoming Car Turning Left

Notice the yellow lights on the sides and the oncoming car in the left-turn lane.

4. Red Lights - Yellow on the Sides

As you approach this intersection, there’s simply not much you can do. The oncoming car is going to get the left-turn light and you will have an extended red.

The Killer

Yellow lights.

6. Yellow Lights - You're turning Right

This is the situation no one likes to see. Yellow lights as you approach the intersection. In this situation, you will stop.

Bonus points: Notice this image has the addition of a right-turn lane. If the white car is turning left, there is a strong chance you will get a right-turn light. If this is the case – and you will know this because you have memorized your route – then you should be able to slow enough to wait for the turn light and then zip through the intersection. However, you must look at the white car to make sure it is in the left turn lane. Additionally, be on the lookout for cars in front of you who do not know there is a right-turn light; they will probably come to a complete stop.

Two Lanes, Two lines of Cars, No Right Turn Light

No picture for this one. As much as I preach staying in the right lane unless passing, this is the situation in which I always get into the left lane. The reason is simple: there’s a high probability at least one of the cars in the right lane is going to turn right. This means cars will lurch forward to go through the intersection but have to slam on their brakes when someone slows to make the turn. On the contrary, every car in the left lane is going straight unless there’s a left-turn lane and some of the cars shear off to the left. Double-bonus!

Summary

I’ve presented some intersection and stoplight possibilities. There are, of course, many more. But hopefully, with these examples, you have seen how important it is to identify the condition of other lights, the position of other cars, and the conditions they might bring about. When you start to notice these things and reacting appropriately, the number of complete stops will dwindle and overall mileage will increase.

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Article,EPA,Hypermiling

Know Your Route

28 May , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

So many times, when it comes to achieving higher mileage, people focus on their car and how they drive. Most times, they just assume the commute is an unavoidable variable. A predefined route that some days has good traffic while other days has bad traffic. This article will explain why the route you take and how you drive it plays as much a role as all other variables. When it comes to improving, never consider anything to be predetermined. The goal is to scrutinize everything.

Find a Mileage Friendly Route

If you happen to live in a large city, there’s a very good chance there are multiple options when it comes to the daily commute. Personally, I have three choices that I will call “Fastest”, “Easiest”, and “Hypermiling”.

“Fastest”: I have the opportunity to hop on an interstate for about ¾ of my commute. Doing so would save about ten minutes and is an attractive option when time matters. The downside is that the interstate maintains a relatively constant 70 – 80 MPH except when it comes to a screeching halt for no particular reason before slamming back up to 70 MPH. In other words, exactly the opposite of hypermiling.

“Easiest”: There is a state highway that runs is literally a straight shot from town to town. Albeit, one with multiple stoplights. Like the interstate, traffic is either racing along (though closer to 50 MPH), stopping for the red light, or accelerating Grand Prix style at the green light. It’s a multi-lane stop-and-go early-morning ball of stress. In no way do I look forward to starting or ending my day on this drive.

“Hypermiling”: This drive is 5 miles and 9 minutes (on average) longer than the “Easiest” route. This drive has longer stretches without stoplights and some stoplights are timed. It passes two schools and one nature preserve. The highest speed limit sign is 45 MPH. It is on this route that I see joggers, walkers, and the occasional wildlife. On nice days, I drive this route with my windows down enjoying the sights and sounds. All the while, the speed is conducive to attentive hypermiling and plays into the capabilities of my car.

By selecting a different route, I can not only achieve better mileage, I can choose how my day starts and ends. If you find that you arrive at work already stressed and you return home mentally ragged, do yourself a favor and seek out a more casual and hypermile-friendly route.

Memorize Your Route

Here is an analogy parents can appreciate. Let’s say your son goes to the first day of school and is presented with a difficult, lengthy exam. How would you expect him to score on that exam? Probably not very good. On the second day, he is presented with the exact same exam. Should he do better than the day before? Perhaps. Let’s pretend your son is presented with the exact same exam every day for the entire 180-day school year. You would expect him to be acing that exam with absolutely no effort, wouldn’t you?

Now what about people working an average 250 days per year? Most of them drive the exact same route every day, to AND from work. Even after all this repetition, it has been my experience that people drive their daily commutes as though it’s their very first time. Every time.

You are a human (I hope). You are preprogrammed to identify and memorize patterns. It’s what we do.

  • Does your commute have a string of fast food joints all next to each other? If so, every evening there’s a strong chance a hungry driver will stop and turn without signaling. Expect it.
  • Do you cross railroad tracks? Make a mental note of when the commuter train comes through. Don’t forget to consider school busses stopping at the tracks during the school year.
  • Timed stoplights? If you didn’t make it from one light to another yesterday, or last week, or last year then you’re not going to make it today. Stop accelerating full-bore as though you have a chance. On the other side of that coin, memorize the speed at which the light will change from red to green as you approach.
  • I have a round-about. I know exactly at what speed I can make that round-about without braking (on a clear day and dry pavement). Coupling this with how far back I let up on the accelerator allows me to coast to the round-about, pray for no cars, and roll through without once touching my brakes.

If you drive a hybrid, consider basing battery usage on drive segments. Pick up some charge during the fast segments in order to run farther on battery during the slow segments. Or vice versa: consider going deep into the battery pack if you know an upcoming faster segment will allow you to recharge. Recharging will impact the instantaneous mileage. Ignore that; it’s the average that matters.

It’s all about driving the same route every day, figuring out what works best, and repeating it.

Summary

If you have the opportunity, drive a route that returns the highest mileage. If it turns out to also be least stressful, then it’s a double-win. The only way to know which route is the most fuel-efficient is to document each pass in order to develop an average and recognize patterns. Once the best route is identified, memorize how to handle each segment with the intent of getting better with each day.

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What Drives Us episode

Check Your Tires’ Pressure

21 May , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

According to FuelEconomy.gov, under-inflated tires can lower your mileage by 0.3% for every 1 psi drop of all four tires. Other sites put the figure at 0.4%. Even though it doesn’t sound like much, the point of this ongoing series of articles to make clear that all things – when taken together – can account for a significant improvement in overall efficiency.

When to take the Measurement

Hot air expands.

That’s it. Now you understand how the temperature of the tire will affect the temperature of the air and therefore the measurement of pressure. Always measure the tire pressure before driving the car. Taking the measurement after a long drive – especially at high speeds – will return a deceptively high reading.

Ideally, you should measure your tire pressure every month. First of the month? Check your pressure.

Winter versus Summer

In addition to hot air expanding, cold air constricts. Most sources put the anticipated psi drop at 1psi for every 10 degrees of temperature drop. In some locations, the difference between the hottest Summer day and the coldest Winter morning could be more than 100 degrees Fahrenheit. For tires, that’s a potential 10psi swing.

When Autumn comes, don’t be surprised if the tires start reading low. It will be necessary to add air to maintain pressure. In the Spring, – and this is important – it might be necessary to remove air to keep the tires from becoming inadvertently over-inflated.

Tires are Part of the Suspension System

Before getting into maintaining and manipulating tire pressure, it should be mentioned that the tires are an integral part of the car’s suspension system. Having shock absorbers is great and all, but it’s the pliability of the tires that cushions the car from all the bumps in the road.

Over-inflating your tires will create a rougher and bumpier ride. It does. There is no way around that. If you decide to over-inflate your tires, you must realize that you do so fully understanding the impact it will have on the smoothness of your ride.

At the Very Least: Maintain Recommended Pressure

door-placardEvery car has a sticker somewhere indicating the recommended tire pressure. Usually, it’s on the driver’s door jamb but some cars have the sticker on the inside of the trunk hatch.

It is important to keep in mind that the tire pressure on the side of the tires might actually differ from the pressure recommendation on the sticker.

The reason for the potential variance is that the tire is manufactured for a wide range of cars. The tire manufacturer does not know the size and weight of the car it will be mounted on. The manufacturer of the car, on the other hand, knows all the variables and calculates their recommendation. This is why you should always refer to the sticker on the car rather than the sidewall number.

If you do nothing else, absolutely maintain the recommendation on the sticker.

The Dangers of Under-Inflated Tires

Most people who have ever ridden a bicycle have ridden on under-inflated tires. Squishy tires make controlling the bicycle very difficult because the rim is sliding from side to side. The same is true on a car except that cars travel much faster and corner much harder. An under-inflated tire could potentially create the situation in which a quick decision cannot be realized with a quick movement.

Do you remember when all those Ford Explorers were losing control and sometimes flipping over? In every case, one of the tires exploded, which make people suspect it was the fault of Firestone. After a bunch of investigating, it was found that in almost every case, the pressure of the remaining tires was low. As a result, it was determined that the exploding tires were cased by under-inflated tires overheating and rupturing resulting in sudden loss of control. Under-inflated tires create additional friction and could possibly become so hot they weaken and rupture.

It has been proven that under-inflated tires are more prone to skidding in the rain, making stopping more difficult. At the very least, braking distance is increased. Worst-case situation: braking distance is farther than the distance to the car in front of you.

Under-inflated tires do not contact the road the way they are supposed to. This affects overall handling and tire wear. Some estimates put the impact of under-inflation as high as 25% faster tire wear.

So there you have it. If you take nothing else away from this article, please check your tire pressure once a month to make sure you are safe.

Exceeding the Recommended Tire Pressure

NOTE: This is a contested concept for the reasons explained below. It is assumed you are a mature and responsible adult capable of making decisions for yourself that affect the operation of your vehicle. If any part of this bothers you, don’t do it. Just because you read about it on the internet doesn’t mean you have to do it.

There are many people on PriusChat.com working to improve their mileage. They employ many techniques and reliably report their results. I mention this because there is substantial anecdotal evidence that increasing your car’s tire pressure can return higher mileage.

The recommended tire pressure for a 2004-2009 Prius is 42psi front and 40psi rear (42/40). The 2psi difference is explained as additional support for the engine in front. Some people increase to 45/43 and report repeatable mileage improvements. Some have gone as high as 50/48 and continued to report even better overall mileage. However, above this pressure, on real significant improvements are realized.

These results – though shunned by many – seem to indicate there is a mileage improvement to over-inflating tires. To a point.

Concerns of Uneven Wear

Many opponents to over-inflating tires use the argument that the tires will develop a bulge and develop a bald stripe along the radial axis. This was true a long time ago. Modern steel-belted radial tires, however, are reinforced in such a way that over-inflating does not bulge the tire.

Concerns of the Tires Exploding

The level to which some drivers over-inflate their tires is only a few psi. Perhaps as high as 10psi. This sounds like a great amount. But the realization that it’s intentionally a fraction of the tire’s potential is not something you will ever see advertised.

I had the pleasure of meeting an actual tire engineer at a car show. I can’t mention his name or which manufacturer he works for. To be honest, it has less to do with confidentiality and more with a horrible memory.

In our discussions, I mentioned that I had inflated my tires above the recommendations and was mildly concerned. He gave a “pa-shaw” sound and rolled his eyes. He then explained that the sidewall tire recommendation is based more on the risk of litigation than the potential of the tire. This gave me a certain level of ease.

Summary

As I look over this article, it’s clear that much of it addresses arguments against over-inflating tires. It’s just that this article only addressed potential mileage gains of over-inflating tires the comments section would light up with those very arguments. So they are pre-emptively addressed in an attempt to make it clear that I’m fully aware of those arguments and am not making blanket suggestions without realizing potential consequences.

Make sure to check your tires’ pressure every month. At the very least, maintain the tire pressure recommendations listed on the sticker in your car. If you choose to over-inflate your tires, be aware that you will experience a bumpier ride because the tires are part of the car’s suspension system. Though there are concerns of damaging tires with higher pressure, the evidence simply isn’t there to support them.

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What Drives Us episode

Be Aware of Your Car’s Aerodynamics

16 May , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

Anyone who has watched Star Trek: The Next Generation understands the futility of the sleek design of the Enterprise when compared to a Borg ship. I call it futility because someone spent a lot of time designing a sleek and aerodynamic design for a ship that will only ever travel in a vacuum, devoid of air (except, of course, when it’s crash landing on Veridian III).

My point here is that when there is no air, the cube shape of the Borg ship is equally as aerodynamic as any Starfleet vessel. Unfortunately, we do not maneuver our vessels in a vacuum; we have to deal with wind resistance and the impact it has on our fuel consumption.

Willie Yee’s Zhang Heng is exactly as aerodynamic as the starship Enterprise. In a vacuum.

Willie Yee’s Zhang Heng is exactly as aerodynamic as the starship Enterprise. In a vacuum.

Because we have to deal with air resistance, we must pay special attention to the way air flows around our cars. One thing is for sure: when a manufacturer puts a car into a wind tunnel, they don’t strap a Thule cargo carrier on the roof and a couple bikes onto the back. In order to earn the lowest coefficient of drag possible, the manufacturer tried to make their car as streamlined and “slippery” as possible. The goal is to disturb the air as little possible. Anything attached to the car will create a lot of disturbance and defeat the intentions.

In this article, we’re going to explore aerodynamics and how keeping your car free from external add-ons will make your car more efficient, improve your mileage, and save you gas money.

Let’s Geek Out on Aerodynamics for a Minute

Before we can delve into how things impact aerodynamics, we should sidebar for a minute and discuss what aerodynamics actually is. The easiest and simplest definition is that Aerodynamics deals with the way air flows around objects. As it turns out, the invisible air we take for granted does some really cool and strange things when objects are pushed through it.

For example, we don’t even consider it but when a car is being pushed through the air, the car is an object that wasn’t in that particular spot just a few second ago. So what? Have you ever pounded a nail into a piece of wood? That nail represents your car and the wood represents the air. The wood was perfectly happy at a state of equilibrium until you came along with your “I have a hammer and therefore everything is a nail” mentality. The nail is literally ripping the wood apart in the same way the car has to separate the air in order to pass through it. Nails are pointed to make it easier; clip the point off the nail and try again. The added effort required represents the wood’s resistance to a having a blunt object pushed through it. That’s visually the same thing as driving a Corvette compared to driving a Hummer.

Aerodynamics_FrontalPressure

Cars and air are different because the car keeps moving, which forces the air to collapse behind it. Air is, for most sakes and purposes, a fluid. Fluids take time to flow from one location to another. Therefore, when the air is collapsing behind the car, there is not an immediate “everything’s back to normal.” In fact, because of the car there is literally a hole in the air. Since the air cannot fill the hole as quickly as the car is moving, there is less air in the space immediately following the car, causing a zone of pressure that is negative compared to the surrounding air. This negatively pressurized space literally pulls the car backwards as it collapses.  The engine is working to push the car forward, splitting the air and at the same time, fighting the pressure attempting to pull the car backwards.  The goal, therefore, is to make one or both of these aspects more efficient.

Aerodynamics_RearVacuum

All manufacturers have to deal with Aerodynamics. Some don’t care; like when manufacturing extra-large SUVs and trucks. Some spend weeks or months in a wind tunnel tweaking and tuning every last bend and curve to improve the frontal and rear aerodynamics. The goal is to split the air and return it to normal as efficiently as possible. To that end, some people are so obsessed that they render – and sometimes create – their own impressions of what a super efficient, super aerodynamic car would look like.

Super-Aero Prius

OK. That should be enough to get the point across. The smoother and slicker the car, the more efficiently it will travel, the higher the mileage, and the more money you’ll save on gasoline.

For a really good explanation and much more information, go to BuildYourOwnRacecar.com. This is where I got the two images from. http://www.buildyourownracecar.com/race-car-aerodynamics-basics-and-design/

Remove Things from the Roof of your Car

The roof is a great place to lug a cargo carrier, kayak, Grandma, or whatever might need to be moved from one place to another, out of sight, and without taking up interior cargo room. But when these things are no longer needed, do yourself a favor and remove them. Too many times, it’s just easier to leave the things on the roof. It makes sense because it was probably difficult to get it all strapped in to begin with and removing it will be a hassle considering you’re going to need it again at some point. But if that “at some point” is in two years when you take another family trip, remove it.

Remove Things from the Back of your Car

By now, this should be pretty obvious. Not only does the bike rack full of bikes represent turbulence, it disrupts the air’s ability to smoothly exit the back of the car. This turbulence creates eddies that increase drag. When you’re not taking your bikes to go riding, remove them from the back of your car.

Make sure your Next Car is Aerodynamic

Perhaps your current car isn’t the most aerodynamic. There’s not much you can do about that now. But you can think about the future. Whenever you’re in the market for a new car, try to make sure the new one is more aerodynamic than the one you are trading in. By doing this, you will continuously make strides towards better mileage.

Summary

The study of aerodynamics is actually really neat and if you have time, dig into it. You should try to purchase vehicles that are designed with a low coefficient of drag because they most efficiently move through the air. Mounting things to the roof and/or the back of the car interrupts the smooth movement of the air, creates eddies and turbulence, and should be removed when not in use.

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Article,EPA,Hypermiling

Follow Large Vehicles (at a safe distance)

9 May , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

First of all, I want to make it clear that this is not an article about drafting. To prove that point, let me explain what drafting is and why it’s dangerous, illegal in some places, and a really, truly, and seriously bad idea.

In auto racing, drafting is also referred to as “slipstreaming” because the goal is to ride in the slipstream of the car in front. In order to do this, the trailing car must be close enough to the leading car to stop the air from collapsing around its back. By doing this, the airflow moves around both cars as though they were one single vehicle. Since much of the effort of propelling any object goes into wind resistance, the trailing car is able to travel much more efficiently. This is shown in the following image, stolen from efluids.com.

Drafting

Drafting is most beneficial at high speeds where wind resistance is great. This is why racecars draft and some people draft behind semi trailers on interstates. Drafting is rude because the trailing car is much too close to the leading car. It is also extremely dangerous because driving can be unpredictable and drafting leaves virtually no room for sudden movements or braking. To reiterate: don’t do it.

So What’s the Difference

Driving behind a large vehicle at a safe distance is similar to drafting only in that the vehicle in front takes the brunt of the air resistance. Unlike drafting, the trailing vehicle is following at a safe distance. The benefit to the trailing vehicle is that the lead vehicle has disturbed the air in such a way that it does not represent as much resistance to the trailing vehicle.

Notice in the illustration above that the air flow lines are drawn parallel to each other in what’s called “Laminar Flow”. Air is illustrated as strata – or sheets – of air that don’t interact with each other. This does a great job of showing that air is moving around the car, but this is not how air really flows. The goal of most automobile manufacturers is to perturb the air as little possible in order to make their car more efficient.

However, there are many not-so-efficient vehicles on the road such as delivery vehicles, semi tractor-trailers, etc. These vehicles have large flat backs and leave huge eddies of air as they travel. Anyone who has ever been standing on the side of the road when a semi tractor-trailer rolled by understand just how strong their wind currents can be. Depending on the aerodynamics of the truck and their speed, their wake can extend hundreds of feet. This is illustrated in the following image.

Semi Aerodynamics

This image is probably the best to illustrate the difference between following at a safe distance and versus drafting. Someone drafting would want to be in front of the red, disturbed air, between the truck and the first marker line. Notice how the dark blue actually curls up and towards the back of the truck? This will literally pull the trailing vehicle towards the truck’s bumper. Following at a safe distance has the trailing car behind the disturbed air, in the light blue area, almost two truck-lengths away. Even at that distance, there is benefit thanks to the disrupted air.

The Other Reason to Follow Other Vehicles

Deserved or not, hybrid drivers have a stereotype of being slow drivers. Sadly, I have seen some cases in which this reputation is strongly earned. Having said that, there are times when I am on a multilane road and I just don’t feel like driving like a bat out of Hell, acting as though commuting is a competitive sport with a trophy handed out if you get to work faster. Perhaps I only want to drive a few MPH above the speed limit and have no concern with keeping up with the general flow of traffic.

Sometimes, I come upon a delivery vehicle or lawn care truck that is driving close to the speed I prefer. In this situation, I will maintain a safe following distance and stay there. There is a very good chance – like many of my phobias – that it’s all in my head, but I like to think that rather than me being the slow car now it looks as though I’m the poor car stuck behind the slow vehicle. But I don’t care because in the end I get to drive at my desired speed. This might sound like a stretch, but I was a little relieved to see a post on an online forum in which someone asked if they were the only ones to apply this technique. Multiple people admitting to it.

At a slower speed, any benefit from perturbed air is minimal if there is any at all. The primary point in following a large slow vehicle is the benefit of not feeling as though you are being pressured to driver faster than you would prefer.

Summary

Drafting is a really stupid idea and extremely dangerous. Following large vehicles at a safe distance can reap aerodynamic benefits without risking your life. Sometimes following slower vehicles gives you the opportunity to get out of the roadway racetrack and drive at a more comfortable speed.

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What Drives Us episode

Drive Less

23 Apr , 2016  

I’m in the process of recording these articles in a series of videos.  Click the image to the left to watch them.  While there, be sure to subscribe to the channel.


-Tony Schaefer

Yesterday was Earth Day: a perfect time to talk about hypermiling and reduced emissions. But I’m not going to. You see, if we really try, we can do even better than hypermiling. In fact, focusing exclusively on driving more efficiently is not always the best approach. After all, it assumes that you will always be driving. Also, there are stories about people literally driving farther than necessary just to make sure their engines warm up so they can register better mile-per-gallon averages.

Today we’re going to shift our focus from driving more efficiently and focus on driving less. There are several approaches to reducing our dependence on our vehicles. This article might not get to them all but hopefully it will serve as a good start and get you thinking.

Walk

The most obvious alternative to driving is walking. OK, I know what you’re thinking: “I live too far from work” or “I have to haul things” or whatever. Yeah, I get that. I have those things too. Walking is not an all-or-nothing alternative. The point here is not to walk everywhere all the time. The point is to know your walking speed and acceptable distance. Then, when you have to get yourself from one place to another, ask yourself whether it is within your acceptable distance. If it is, seriously consider walking.

On a more personal note, we have become a sedentary society. We sit in our car, at our desk, and in front of the television. No matter who you are or what your current state of health might be, we can all benefit from taking more steps every day.

Bicycle

Stepping up from walking is riding a bicycle. The same concept applies: know your acceptable distance and situations. If the current need fits your parameters, ride your bike. From time to time, someone at the local fitness center will wonder why there are so many parking spots and so few bike racks. This is a perfect example of when to ride your bike.

Not only does bicycling extend the distance and shorten the time compared to walking, mountable carriers allow for light grocery shopping. If you need to run to the local store for a few things in order to complete the recipe, don’t bother firing up the vehicle; hop on your bike.

Carpool

Some of us are lucky in that we have coworkers who live within a mile or two of our homes. This makes carpooling pretty convenient. Some companies have bulletin boards where people can post interest in ride sharing opportunities. Some are actual bulletin boards in a common area such as the cafeteria whereas tech savvy companies might have information on their intranet.

When it comes to driving less, any improvement is an improvement. Let’s say you have a coworker who lives halfway between you and work. Even if you drive to their house and park your car, you are not driving the entire trip. Even if the coworker lives a few miles out of your way, the fact that you are not driving every day means that you are driving less.

Of course, carpooling means taking turns. Don’t be a carpool leech! The only acceptable exception is that you do not have a car at all.

Mass Transportation

Some people have mass transportation options and don’t even realize it. Make sure to check your community’s internet site or other information to see what mass transportation options exist.

Some people place a stigma on riding the bus or train. Their belief is that not rolling up in your own set of wheels somehow makes you less of a person or they see mass transportation as a lower form then car ownership. But these people are spending money on gasoline and potentially on parking fees. They log more miles on their car, which will result in faster wear-n-tear maintenance. They aren’t aware the amount of money they are spending just because of their personal belief.

Those who ride the train and/or bus to and from work do not have to drive in the rain or snow. They save money on gasoline and potentially parking fees. Ridding as a passenger is much less stressful than driving and provides ample opportunity to get a little more work done, sit quietly, or catch up on that podcast.

Plan your routes

Have you ever been our in your car running a few errands and realize that you’ve crossed town twice already and will need to do it again? Hopefully, it occurred to you that had you planned your errands a little better, you wouldn’t have to do so much driving around.

Not only does better planning reduce the miles you log in your car, it saves you time and money. You save time because, of course, you spend less time in your car. You save money because gasoline is not cheap.

Next weekend – or whenever – when you are about to run a series of errands, consider writing them down and then numbering them based on a preferred route. You would be surprised how much time you end up saving this way and how much better you feel for having gotten through them faster.

Conclusion

Reducing the miles driven in your car by any amount is an improvement. Even if carpooling and mass transportation are not available in your area, you can still find other ways to drive less by biking and walking from time to time.

Here is my biggest rub. I pulled these tips from international sources. These things are tightly integrated into the very fiber of most Europeans. Trains and buses are used to capacity and many companies have as many bike racks as parking spots. Some European companies charge their own employees for parking in their garage as a way to encourage carpooling and mass transportation. Sadly, these things are usually either ignored or rebuffed by most American citizens. I shutter to think how bad things would have to get before more people here started acting more like the people over there.

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