Pick up trucks pushing

This has been discussed ad nauseam on this site around 2009-2010 (you can search) but the gist is the European Union requires adherence to UN ECE Reg 39. It says no speedometer can read slower than the actual speed. It's allowed to read up to 10% over the actual speed. The Prius is built in Japan and follows this reg first irregardless of being sold in the USA. The USA has no law on speedometer regulation. Japan has SAE J1226. It's 4% +/- but over the entire speed range. Because of Reg 39 they err on the high side.

Light searching yeilds this among many others.

My 2000, 2001, 2014 4Runners were like this as was my 2010 Prius and my 2014 Camry Hybrid. This is not new news.

 

My father used to drive a 40’ diesel pusher motorhome as apart of our business.

The sad part is the highway is becoming a gradeschool version of recess.

His motorhome really only went around the speed limit towing a trailer, some folks would still behave like he was driving a moped or a Prius and try to intimidate him, there were a few close calls that hopefully scared the crap out of the people who never learned how to drive, one thing we did learn was no matter how many trucks were blocking his way to exit he just had to slowly merge over, there might be more honking but nothing ever contacted us, it all was out of his way

What I’ve learned is that I just ignore flow of traffic and follow the law, I have avoided several large pileups on the highway because of that and no matter how fast I go I still have some jerk causing problems going faster and usually flipping me the bird, I actually have fewer issues going nearer the minimum limit because the zombies just pass, around 5-10 over the limit I have had several near misses with bumper taps, one guy spilled his Jeep , I was going 10 over a 55mph road, he was likely going close to 100, road was empty and multi laned, after that I quit caring and I do keep a close eye on my rear view mirror and flash 4 ways if needed or take evasive action.

 

1 You have the right of way, to be courteous you can change lanes if you also have that right of way.
2 No..... 49 CFR 393.82 - Speedometer. Each bus, truck, and truck-tractor must be equipped with a speedometerindicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).
3 Scangauge is going to give the same speed as the speedo which is reading whel revolution, if you have 195/65-15 tires your speed is calibrated correctly, my 06 came with 185/65-15 tires, my 11,16 and 17 all came with 195/65-15 tires, the 17" whel prius are undersized and give a low speedo reading.

 

As far as I know, the speedometer must never read lower than actual speed, which makes sense I think.

 

So, does the calculation of mpg and distance use the (false) speedometer reading as well?

 

Yes.

Bob Wilson

 

I was gonna say no, lol. The speedo display is just that, a display, fudged a bit by legislation. As far as I know, behind-the-scenes the car has a reasonably accurate reading of distance travelled and fuel consumed, does the usual calculation, and then "cooks the books" (by order of the sales department?). How else to explain a relatively consistent error?

 

Riding motorcycles earlier in life taught me to believe nobody else sees me. I drive the same. The mergers to on ramps rarely look to comply with "merging responsibilities". Anticipate the worst scenario and drive defensively. Forget mpg's and avoid the very expensive hassles of a crash, regardless who causes it. Not interested in #2 or #3 issues.

 

What I found is changing the tire ‘revs/mile’ solves odometer, speed, and MPG errors. The fuel consumed is accurate regardless of tire diameter.

Bob Wilson

 

I'm an expert at driving the speed limit, having done so for decades. Now just to be clear I don't look down on the 99% of my fellow citizens who do not drive the speed limit unless everyone else is, or if there is a cop around. First of all my minimum speed is actually 5 mph over the speed limit, which accounts for approx 1.5 mph difference between my speedometer and actual speed, the other 3.5 is my little compromise with everyone else. However if I am in a hurry I go 10 mph over the limit. If I am in a REALLY big hurry like about to miss a flight then I flow with the traffic and I am grateful when everyone else is going 20 mph or more over the speed limit . But any other time I do my 5 mph over which is most of the time. But I realize that 5 mph is annoying to many other drivers, which is not my intention.

However safety is paramount and when I am doing my normal 5 mph over the speed limit I ALWAYS drive in the far right hand lane. It's not the nicest place to be much of the time, in fact I call it driving in the gutter. You have to watch out for when the right lane suddenly becomes an exit only lane, and for merging traffic, people changing their tire on the side of the road, etc. But I feel it is my lot in life since it's my own decision to drive close to the speed limit, so I have in effect banished myself to the far right hand lane. I am used to it, and if you stay alert it's no problem. While I do think it is unsafe to drive slower than the flow of traffic in middle lanes, driving in the far right lane at the speed limit in my opinion is not unsafe, because people expect slower cars in the right lane. They may not like it and they may get on your tail, but generally they aren't surprised, whereas they don't expect slow cars in the middle lanes. I am not one of those people who feels that going the speed limit gives me the right to drive in any lane that I want. I know my place, it's in the gutter.

However I do understand people driving slower than traffic in the second lane from the right if they are towing trailers etc. because they can't react as fast to mergers.

My best friend is my cruise control. I use it even in moderately heavy traffic (obviously not bumper to bumper or stop and go). I know some people think it's unsafe to use cruise control in traffic, but my foot is right there ready to brake, and my finger is one inch from the cruise stalk, ready to adjust or cancel, in fact my finger is often riding on that stalk (I don't have dynamic cruise yet). And I am staying fully alert of my surroundings. I think it's safer because I am going a steady speed so other nearby drivers won't be caught off guard by speed changes, which in my opinion people whose speed is constantly changing are the greater hazard. Yes I could drive steady speed even without cruise control, but that takes attention to the speedometer, I prefer to keep my attention on my surroundings. And when someone gets on my tail I think it reduces my chances of being rear-ended if I accidentally slowed down. And I notice that when my speed is rock solid steady the tailgaters move around me more often than not, whereas if you speed up even 1 mph they are like sharks smelling blood, or dogs sensing fear, they become even more aggressive if you don't keep speeding up. In all these decades I have never been rear-ended even though I hear endlessly that it's impossible to drive the speed limit or "you will be run over". Funny in over forty years of driving the speed limit I haven't been run over.

Okay mergers. Cruise control really helps as it gives the car that is merging a steady moving target to work with. If they merge in front of me going faster than me, perfect. If they merge in front of me going slower, I slow down and give space. Same if they are going my speed but pull right in front of me, I slow down and give space. If they merge behind me and are immediately on my tail, I keep the cruise nice and steady. Normally they won't be there long.

The tricky ones are where even though I am rock solid on cruise, it becomes obvious that their speed will put them right next to me when they run out of runway. It actually doesn't happen all that often, but when it does I don't flinch, I keep the cruise locked. They know I'm there, it's their problem to deal with since they created it , they saw me and just assumed that I would get out of their way. I'm not doing it to be spiteful, actually I think any sudden moves that I might make at that moment including making a sudden lane change to the left is itself hazardous to myself and other drivers. So I leave it up to them to either hit the brakes or go into the shoulder. Yes they honk and get mad. Haven't been shot at yet, haven't been broadsided yet. Just made a few people mad.

 

Single lane is a bit different. If it's just you and "the other guy" there isn't much you can do, I just keep going the speed that I was going, and eventually they will either find an opportunity to pass, or there will be a passing lane, or they will back off, or they will stay on my tail. Sometimes you find yourself in the same predicament, following behind a slow moving vehicle on a single lane road. So it happens to everyone, some people just react more maturely (and safely) than others when stuck behind a slower moving vehicle.

When someone is passing me, if it looks like they might be running tight with an oncoming car I slow down a bit to help. I have heard people say no way they never slow down, it's that person's fault for passing when there wasn't enough room. Well maybe so, but passing isn't always easy because it's hard to judge the speed of the oncoming car, and I don't mind helping someone out if it's getting a bit tight.

It's a bit different if there are a lot of cars on the single lane, in that case there is essentially a traffic flow. Which you soon discover when you have a line of cars behind you. Unless there is a passing lane coming up soon, as a courtesy I will either speed up or else look for a place to safely pull over if possible and let everyone pass. Some roads even have turnouts for this purpose. If there isn't a safe turnout then I will normally speed up, at least as much as I think it's safe to do so.

 

On single lane roads near me, if I travel at 61 MPH, I pass as many vehicles as pass me.

 

On single lane, when I've got a train, I'll sometimes pull over, let 'em tear off to their pressing appointments.

 

Bob, I don't believe that to be true... at least not fully. At some point, the dead-reckoning of tire rotation and direction must match up with GPS within the nav system. So at some point the car knowns actual speed.

It's very, very accurate... when driving into NYC and taking one of the tunnels there is a marker in tiles on the walls for the dividing line between NY and NJ (state border). I've driven this more than enough that when the map is zoomed in all the way, the cars position marker exactly matches up with the map.

 

The question: Pick up trucks pushing | Page 2 | PriusChat

So, does the calculation of mpg and distance use the (false) speedometer reading as well?​

Yes.

Bob Wilson

 

Don't know why you'd say that Bob. The car has the odometer info, and the fuel flow: isn't that what it'd use?

 

The tire diameter is off so the revs/mile are in error. Once you quantify the error, identify replacement tires that correct the problem:

1. Drive to a road with mile markers and plan on a 100 mile trip.
2. Reset the tripmeter when passing a mile marker.
3. Calculate the odometer error versus the mile markers after 100 miles.

Go to TireRack.com and look for replacement tires whose 'revs/mile' equals the correction factor. Then plan the replacement.

Bob Wilson

 

In theory but I doubt it. It's back to the discussion of why doesn't the GPS set the time on the dashboard clock. GPS systems seem to be in their own little silo, operating within the central MFD along with audio and climate control. It seems to be true in most cars not just Toyota that the central MFD is a separate system from the "instrument panel" (using an older term) which displays information about the car such as speed, odometer, tire pressure, mpg etc. Confusing the terminology a bit is that most cars now have a separate smaller MFD within the instrument panel.

I am not aware of any car where the central MFD system talks to the instrument panel. Maybe some do but any car I have driven (lots of rentals) I get the feeling that these are separate systems. In theory the two systems could be connected, but from a engineering standpoint I think the hardware is all different, for example a car maker can have different central MFD's available within a model, or completely revamp the central MFD in a new model year, none of which impacts the instrument panel since it is a separate system. Tying it all together is possible, but apparently not currently worth the trouble just to get accurate speed and mileage indications (and dash clock). Worth the trouble to us I suppose, what I mean not worth the trouble to car makers, unless they are one day mandated to use GPS for speed and odometer.

 

Are you saying that the odometer is exaggerating distance travelled, enough that a tire upsize is needed? Say two percent? Isn't that the stuff of law suits?

I appreciate the speedometer is off, but that's irrelevant, wouldn't you say?