How the Prius wastes fuel
 

I often come across eco drivers who do not respect the slower traffic kept right concept, or eco drivers that interrupt the flow of traffic because they are oblivious of anything that is going on around them. There are other vehicles that do this, but the Prius seems to be the main culprit. For years, I have noticed that when I come across an interruption in traffic flow, it is so often a Prius with nobody in front of him that is causing the problem. I respect eco drivers who can do their thing without interrupting the flow of traffic, but have resented the ones who don't for years. Anyway, I started keeping track of what happens when a Prius interrupts the flow of traffic a few months ago, and thought I might share it here.

One of the big things that helps out economy when eco driving, is to not interrupt kinetic energy, kinetic energy being "something in motion tends to stay in motion". A good eco driver knows to not speed up and slow down too much, and to use the friction brakes as little as possible, and this preserves kinetic energy. I have been researching kinetic energy usage for years in the electric vehicles that I build, so I have plenty of instrumentation on board my electric metros for measuring energy usage. I can plot and record graphs of my battery pack, amps, volts, rpm, speed etc, as I drive. When I encounter a Prius that is causing a resistance in traffic flow, I can see that the interruption of my kinetic energy wastes a few watt hours everytime it happens. It is not really all that much of a waste, and I can often make efficient driving choices to minimize the waste, but most cars do not.

Wasting a few watt hours everytime I come across a Prius is pretty trivial if you look at how it effects my fuel economy, especially considering that there are few EVs, if any, as efficient as mine, but if you imagine the number of gasoline cars that waste five times more energy slowing down to navigate past the Prius and the speeding back up after they are past, the fuel waste would be incredible. Wherever the Prius is, there is a resistance in traffic flow that wastes the fuel of all the cars that finally get by.

I see a lot of focus on weight and aerodynamics by those who are interested in fuel efficiency, but not a whole lot on managing kinetic energy. Many knowledgeable eco modders are aware that it is important for eco driving, but I am not sure if many realize just how much kinetic energy we waste while we drive. I have been studying it for years as I build efficient EVs, and I assure all that we waste way more fuel than most realize by not managing the kinetic energy.

The speed limit is the maximum speed allowed on the stretch of road. Few roads have a minimum speed limit but they do exist. It's my opinion that if people paid more attention to the road in front of them and their mirrors that they'd be able to see the gap closing on the slower car, safely change lanes, and pass the slower car without ever slowing down. The waste of energy comes from poor drivers more so than slow drivers.

Must be different out there. Most of the Prius' I see are driven like they're stolen.

Me too. Like they're stolen. See it all the time.

It never ceases to amaze me how fast people crawl up my tailpipe, sometimes visibly slamming on the brakes before rapidly jerking the wheel to swerve around me. As if you couldn't tell you were closing in on me the last several miles until you were 20 feet off my bumper? Sorry to interrupt your texting. :/

My father recently had the choice between driving a Ford Escape and a Prius on a 2000-mile road trip. He chose the Escape. ��

He's not a rich man... go figure.

Sorry to go off topic, but it suddenly occurred to me how many other interesting model names a PC keyboard can yield.

Ford Escape.
Starting the trend they took the key in the upper left corner.
Some racing organization claimed the next row of keys.
French estates are often called Break.
Suzuki has the Alt(o) and the Sh(/w)ift. Honda the Del (Sol).

But then. Who will claim Scroll Lock?
Where is the Nissan PageUp? Smart Alt Graphic? Chevy Control? Toyota End?

Back on topic.
I can see accurately how much fuel I use and how much speed affects that.
It seems that traffic in general moves way too fast.
That Prius, if it abides the speed limit, is not doing anything wrong.
If other drivers choose to ignore the speed limit and drive at a speed where they waste fuel by the bucketful, not anticipating cars up ahead that do move at a more reasonable speed, it is entirely their own fault.

There is a psychology factor too.
If the 'slow' driving car is anything other than a hybrid you would not register it as someone trying to save fuel. Just someone that drives the speed limit, for whatever reason, be it comfort, having the time, following the rules.
Maybe they like their car and are not in a hurry to abandon it at their destination.

But when it is a Prius you automatically assume it is to save fuel. It becomes an issue. And you remember getting held up by a Prius.
That's why it always is a Prius. You forget the rest.

Unless you drive at the speed limit yourself.
I cannot remember getting held up by a Prius in the last year.
I get passed on the motorway by at least 50 Priuses every day.

It all is just a matter of perception.

I think people see what they want to see and conclude it's the dominant behavior: "disruptive Prius drivers" and "bad BMW drivers" and "Mustang drivers crashing into things when leaving cars & coffee events."

Confirmation bias: a tendency to search for or interpret information in a way that confirms one's preconceptions, leading to statistical errors.

I agree.

Again, I agree. If we had a world of good drivers who knew how to make the most of their fuel, everybody would share the rewards. I share your opinion, but unfortunately I can see that this will never happen in the real world.

This is where it gets complicated. You just summarized the types of drivers out there as either poor drivers or slow drivers, but this may not be reality. It is quite possible to have a poor driver who is also a slow driver, and it is very possible to have a fast driver who is a good driver. In the case of a Prius causing resistance in the traffic flow, if the driver of the Prius wishes to impose his idea of how people should drive, he will cause a change in the speed of the traffic that flows around him. This change of speed would not occur is all drivers were skilled eco drivers, but unfortunately the world is full of poor drivers.

I see a lot of Prius' being driven like they were stolen out here as well. Not every Prius is the problem, and much of the problem comes from other vehicles. My confirmation bias is what initially directed my attention to the Prius, but my research has shown that the Prius is indeed the dominant offender.

Exactly. The eco driver may not be the one doing something wrong, and there is a never ending supply of drivers who do what you just described. This accurately describes the never ending changes in the kinetic energy of all the cars who are passing the eco driver. The fuel waste is indeed the fault of the guy who can't manage his kinetic energy, but in the case of many eco drivers, much of the blame goes to them as well. The Prius in the left lane with nobody in front of him and 20 cars behind him is introducing resistance in traffic flow that will waste far more fuel than the few drops that the Prius saves. If the Prius driver were to stay right and out of the way so that the rest of the traffic could flow normally. there would be fewer changes of kinetic energy.

Yeah, I have yet to see anybody trying to hypermile in a Prius in the Idaho area.

"Why bother? It already gets amazing gas mileage! Better than my big truck!"

I always giggle a bit when I get passed by one.

Ya know what REALLY irks me? When you are in the right lane (or 2nd to right, because of exits) with 4+ lanes on the highway and people would rather come up on you, hit the brakes, wait for you to speed up (and you don't, of course), so after some tailing, they FINALLY go around. The whole time, they could have simply swung into another lane and never moved a foot of the accelerator! I find that people are FAR more wasteful in 3+ lanes than in 2. If I'm on the right going at a turtle's pace, people normally get over a lane and pass, but it's rarely the case with more lanes, no matter what lane you get in.

http://i0.wp.com/bitcast-a-sm.bitgra...Bob-Barker.jpg

It's not my fault that someone decided to take a swing at Bob Barker. Who won that fight, anyway?

This is good stuff. Confirmation bias is what initially directed my attention to the Prius, and confirmation bias is what causes Prius fans to oppose an idea in a thread that attacks the Prius. In my case, my dislike of the Prius and the research that I do anyway that studies the waste of kinetic energy in automobiles is the perfect storm. You are quite right that people see what they want to see, which is why Prius fans will block the science of what I am saying without conceiving the actual resistance in traffic flow phenomenon. I see what I need to see in my kinetic energy waste research, but the traffic flow phenomenon that the Prius introduces is not the main purpose of my kinetic energy research. The main purpose of my research is the development of efficient EVs, but it also makes it really easy to satisfy my confirmation bias about the Prius.

Being the EV snob that I am, and since I don't like the Prius, I always joke about them to my family when we are passing a Prius. I call them gross polluting fuel hogs.

Many of the Prius' that I see around here have drivers that don't look engaged with what is going on, and I regularly see the drivers seat pushed as far forward as possible with a driver who is barely in touch with what is going on in front of the car. All too often, the Prius' that I see around here are like random floating bad guys that you have to watch out for in a video game so you don't lose one of your three lives. When I get up beside a Prius and look inside, it is apparent that the radio is turned off, even though I would not be able to tell if it was not. Just the clueless look of the blah looking drivers and the seat all the way up tells me what is going on inside their car. Nothing. I also see Prius' driven like they are stolen, but nowhere near the number of clueless ones.

I would have to say that, in my admittedly limited experience driving through the Sacramento area, driving slow in the fast lane is not an activity limited to prious drivers.

People perceive me as being an impediment to traffic in my Prius, but that's only because they only think 20 ft ahead of their bumper. One instance where people get angry at me is an on-ramp to a highway that has 2 lanes that merge into 1. I accelerate slowly up the on-ramp knowing that people will be slamming on their brakes because they don't merge smoothly. Everyone behind me gets angry that I didn't follow everyone ahead in the accelerate -> brake ritual.

Another thing I do in the Prius to preserve the kinetic energy of all the drivers behind me is to drive the average speed in stop and go city traffic. Sometimes an increasing gap forms ahead of me, which annoys some drivers behind me, and other times I'm coasting and closing that gap. Everyone behind me ends up utilizing their brakes less frequently, and we end up arriving at our destination within seconds of when we would have arrived by tailgating.

My useless anecdotal evidence today had a Ford F250 take an eternity to make a right turn, causing a disruption in the flow of traffic. He came to a dead stop before making the turn, even though a stop was not warranted.

The other car doing 35 MPH in a 40 was a Honda Accord.

I will not delude myself into saying this worthless anecdotal evidence is scientifically rigorous research.

This thread should be re-titled, how thread posters waste time.

Yes, this thread is disrupting the smooth flow of information to my head.

Whoa! Hold up there, cowboy. The other posters here aren't calling your anecdotal evidence into question because they like the Prius; they're calling your anecdotal evidence into question because it is anecdotal evidence.

Say it with me now: Anecdotal evidence DOES NOT EQUAL statistically-viable sampling.

Again: Anecdotal evidence DOES NOT EQUAL statistically-viable sampling.

You're looking at cars you see in your regular driving, which likely includes many of the same people who also live in your area and travel the same routes regularly. When you remember seeing Priuses holding up traffic "all the time," there's a pretty decent chance you're only seeing the same handful of cars over and over; if you think you aren't, you need to produce some evidence that convincingly demonstrates otherwise. That said, we also don't know anything about how you are recording your encounters with said cars holding up traffic. Are you recording them in some way? Or just relying on your fallible human memory?

To recap, the problems with your argument are:
1) No sampling methodology beyond "whatever cars happen to be travelling the same stretch of road as I am right now." You may see the Prius holding up traffic in front of you and miss ten cars of other makes doing the same thing within a one-mile radius at exactly the same time, or in the spot where you were but ten minutes later.
2) Poor sampling methodology means your sample is not representative of the population as a whole, so any results you get cannot be generalized.
3) We don't know if you have any system for recording the incidences of cars holding up traffic at all, let alone how detailed it is if you do. If you do have a system in place, you should have no trouble answering the question of how many cars you observed driving the speed limit or below on March 7 of this year, how many of them were Priuses, how many cars you observed driving above the speed limit on the same day, and how many of them were Priuses. And without that information, your evidence is meaningless, even completely disregarding the sampling error.

Once more, for old times' sake: Anecdotal evidence DOES NOT EQUAL statistically-viable sampling!

I think most motorists when not using cruise control are spazzes. They couldn't hold a steady speed if their lives depended on it. The eco driver no doubt in some cases introduces a kinetic ripple but then again the whole damn thing is a series of ripples anyway.

Ah, yes, the "slinky-oscillation" method of convoying!

Couldn't agree more.

Except for Mustangs and Cars & Coffee. That one is demonstrably true, going by the sheer amount of video evidence online. :D

Where I live, the dominant behavior is to drive like you want to get somewhere, and the vehicle in which people do that is a secondary detail. I think a lot of people purchase the Prius so they can get good fuel mileage and they don't have to think about how it happens - which is a defining characteristic of how they drove before they had a Prius.

To their credit, they chose a Prius. That they leave a tremendous amount of potential unrealized is unfortunate, but that's a product of their habits. They nevertheless opted for a thriftier vehicle.

When you think about it, there aren't many vehicles out there that will do more for you automatically than a Prius. Is it any surprise, then, that they aren't driven in a mindful manner? The vehicle itself doesn't encourage mindful behavior.

I'd like to add that it's not the Prius that's the problem, it's whomever is driving that Prius. Is there some quality in a Prius that tends to attract drivers that have this behavior you don't like? Maybe, maybe not.

Lol, very true. The Prius seems to be the dominant offender, but I see all kinds of vehicles interrupting the smooth flow.

I had one of those situations this morning. An Aveo sedan was all over my bumper for not trying to catch up with the cars ahead of us. Long story short, we're looking at almost 20 miles of effectively no passing. If traffic is sparse you can pick off one or two here and there, but in the morning commute you're looking at blocks of 10 or 20 cars- you're not passing the whole group and there aren't any holes to fit into. Even if you succeed with a pass, congratulations! You're now one car ahead in that 20 mile long line. There's a mile long climbing lane, but you're not going to pass a group of 10 cars- half of which are trying to pass the other half, who think "two lanes, it's a different kind of road now and I can drive faster." Oh, and past that is a detour with a stop sign.

So this Aveo strained uphill past me to catch up with the line of cars that was approaching the stop sign. And being in an Aveo, she had to wait at the stop sign for a huge gap in traffic before she could proceed. I wasn't upset at being delayed by her at the stop sign because I knew we'd catch up to the larger mass of cars soon enough, and when the road really opened up in a few more miles her pass would get her there one car length sooner, and me one car length later. Over 40 miles that's not really a delay, and now I had a draft instead of just someone filling my wake.

Many people are just plain stupid. They don't understand simple things, and traffic patterns are apparently complicated. I don't take the blame for wastefulness created by people reacting to my attempts to minimize my own waste: If Happy gets mad at me and punches Bob Barker, I don't really give a #V(%; he's an idiot and it's on him.

To me it's not so damning that EVmetro loves the anecdotal, it's the assignment of responsibility. We're all responsible for our own actions unless we're irrationally annoyed by someone else's perfectly reasonable behavior? Wrongheaded statements like that make me so mad I'm going to stomp on my glasses. We all know whose fault it'll be, so I'll PM EVmetro a pic of the bill for replacing them.

So true. I don't have driving experience in a Prius, but I suspect that there may be instrumentation that would help the driver achieve better fuel efficiency, at least for his own vehicle. I have used the Scangauge2 back in the old days, and found that if I used it religiously to drive more efficiently, it really boosted my economy. I suspect that there is more to it than just the Prius driver driving for economy. Perhaps the Prius attracts a large number of blah people who are clueless about driving. The Prius itself seems to be a remarkable machine, but perhaps many of the drivers are not exactly car enthusiasts.

In defense of the eco drivers who drive the Prius, if efficiency for your own fuel is your only concern, doing 55 in the hammer lane will indeed yield better efficiency, but if overall usage of fossil fuels and its impact on the environment is your concern, you will have to eco drive more wisely, and in a way that may increase your own fuel consumption from time to time. Driving the speed of traffic may use a little more fuel in your own car, but could save a lot more fuel for everybody else.

Excellent, I agree. one of the biggest things that I know of that can be done to achieve better economy is to purchase a vehicle that is fuel efficient in the first place. I love to watch people do mods on their cars for better economy, but just selecting an efficient vehicle does wonders.

The wasteful drivers will never stop being wasteful idiots, and there is a never ending supply of them on the road. Minimizing your own waste is golden, but in many situations, minimizing your own waste will maximize the waste of the never ending supply of wasteful idiots. The burden of common sense is on you if you care about waste, but if you impose your driving style onto the wasteful drivers, there is even more waste. Once you master minimizing your own waste, you can expand to minimizing the waste of the wasteful idiots.

What's the first rule of ecomodding? [I"]ADJUST THE NUT BEHIND THE WHEEL"[/I]
That would alleviate most bad traffic of any kind. Of course until the autonomous, robotic cars take over this won't happen. I wonder if autonomous vehicles will learn to have road rage with other autonomous vehicles...or even with human driven vehicles. Can't wait to see.
JJ

A "kinetic ripple" is such an excellent way to summarize what I have been getting at, thanks. I am not so great with words, but that describes in a nutshell what I am talking about. I will probably hijack that term for the future. That kinetic ripple can create an incredible amount of fuel waste in certain conditions, since the ripple leaves a wake everywhere it goes. The kinetic ripple is more difficult to conceive for those who wish to impose the way they think wasteful drivers "should" drive onto them.

Generally speaking, having cars get behind a slow driver tends to save fuel for everyone. Maybe the drivers are annoyed by the slow driver, but that driver is certainly not hurting their economy.

In many cases, eco-drivers will greatly improve the economy of tens, or even hundreds of cars in a traffic jam by moving at the average rate of traffic, rather than accelerating and braking. Cars behind them end up doing the same thing, and the gas savings are multiplied.

I agree that there are many times when you actually can "impose" fuel savings onto wasteful drivers if you know what you are doing. The Prius controls the kinetic ripple, so if you know what you are doing, you can control it somewhat. Kinetic energy is "something in motion tends to stay in motion", and the best way to do this is to not create the kinetic ripple in the first place. If traffic is flowing at 75 mph, but has to temporarily slow to a 65 mph speed limit to navigate around a Prius that is clogging the flow, and then speeds back up to 75, there will be a large ripple in the kinetic energy that will be continuously wasting fuel. If you steady the flow of stop and go traffic by not racing up to the car in front of you and slamming on the brakes, you may be able to actually keep the cars behind you at a more steady pace, preserving the kinetic energy.

So, this thread isn't about how the Toyota Prius wastes fuel, but instead about how our behavior impacts the fuel economy of others.

That sounds similar to:

http://ecomodder.com/forum/showthrea...mpg-27196.html

Perhaps. I still see the Prius as the most common culprit. There is something special about the Prius that attracts problem drivers, and what ever it is, it makes the Prius into a fuel wasting machine. If you feel defensive of the Prius, you may not ever be able to witness the phenomenon or conceive what the kinetic ripple is, but if you happen to be objective and interested, start watching what vehicle is the source of the clogged roadway. Sure you will see people too old to drive, and maybe a few drivers who have learned how to drive in another country, but try keeping track.

In my area, it's usually pickup trucks. Most Prii are here are the fastest cars on the road, doing 70+ in 50's.

I did not think much about Prii until I bought my Forester and longed for far better fuel economy. I would mention it and people would interrupt me to say Prius drivers always cut them off, were the fastest on the road, etc, so I started noticing Prius drivers passing everything. My sister and I drove to California and I pointed out many Prii passing us. I probably stopped caring, that seems more likely than Prius drivers going slower. I see many people complain about people driving slowly in the fast lane, but I have never seen it, I once took a picture of a school bus driving 55 in the carpool lane, but as soon as I got it, the bus sped up. My experience has been like NoD's, I generally stay in the slow lane, but I attempt to minimize how much I am in other driver's way. However, people insist on trying to speed in the slow lane. I imagine we are mutually incomprehensible, if you want to driver faster, why waste time tailgating me, why not just change lanes and drive faster?
Maybe they do not honk, flash their lights, and make rude gestures at NoD, but that is my experience.
Speeding seems far too stressful.

In my area the Prius is the car that is always going way over the speed limit also.

My wife and I made a trip last month to the Fairmont Hot Sprigs in Montana. Montana has increased the speed limit to 80 mph on some parts of I 90.

As soon as we hit the 80mph speed limit I noticed all the traffic was now averaging 90 mph. So I increased my speed to 90mph to keep from getting ran over. Then after about 20 minutes I noticed a Prius flew up on me like I was standing still. So I increased my speed to the same as his to see how fast he was going. Well it shocked me we were doing 105mph. My wife woke up from her nap and ask me what the Hell are you doing? I said trying to keep up with this Prius thats in front of us.lol She gave me the look and I slowed back down to 90mph. Then a lifted diesel truck flew past us and was on the Prius ass. The Prius stayed in front and started to pull away from him. Eventually I could no longer see them as they disappeared in front of me. About a 1/2 hour went by and I came up on the same diesel that was following the Prius earlier but this time he was only going maybe 55 mph at the most blowing smoke out from the engine bay. :D

I have seen a lot of posts on this thread where members been more interested in defending the Prius than actually conceiving the kinetic ripple. For those who prefer to debate that the Prius does not cause the ripple, try typing "slow prius drivers" into your search engine, and see for yourself. There must be some reason why there are so many results.