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Old 04-15-2015, 03:56 PM   #1
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determining highway vs city percentages

when entering my weekly fill up stats, i have often wondered when you input the percentage of city vs highway driving, do you base it on actual driving time or actual mileage driven?

for example, i leave the house at 6:00 am, I am in town at 6:30 and arrive at work at 7:00...so if i base it on time i would say its 50 / 50...but if i do it by miles driven, then i would say its 70 highway and 30 city.

what is the correct way?

scotty
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Old 04-15-2015, 04:43 PM   #2
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It's entirely arbitrary. There is no definition for "city" or "highway" driving.

Some places have 55mph highways with no traffic, whereas in places like LA a "highway" trip often consists of the 0-85-0 dash repeated for hours, even if you are just going a few miles. But both would be considered "highway."

Likewise, "city" driving may include lots of stop and go traffic, or just slower speeds with few stops.

Just define your own data in a consistent manner, and you'll be able to use it to analyze one tank to another. But it's a fool's errand to judge two drivers' data based on their individual use of the city/highway percentage. It's not really useful in that way.
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Old 04-15-2015, 11:59 PM   #3
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You can decide not to show the city/highway data in the settings inbound wish. I've said before, where I live, there are no "cities" or "highways" so I just count the main roads as highways, and assume all my short trips are "city" but it's all guesswork anyway.
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Old 04-16-2015, 07:01 AM   #4
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Apologies, still getting used to predicted text. "Inbound" should be "if you" in my previous post!
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Old 04-18-2015, 06:48 PM   #5
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This is my formula, using the average speed for the tank:

The EPA estimates 21 MPH and below to be "100% City", and 48 MPH and above to be "100% Highway". So where your average speed falls in that magic 27-mph span between 21 and 48 determines the percentage.

I reset the average speed at every fillup, and use the total to determine my percentage. The equation goes like this:

(your average speed) - 21 = X

X 27 = your highway percentage

100 - (your highway percentage) = your city percentage

It's still a subjective number, as pretty much anything you do is only an estimate. But it's one way to make it quantifiable and repeatable and consistent, so it's what I use every time. My SVT Focus doesn't have a readout for average speed, so I just don't show that field for that particular car. But my other three all do, so they get "the formula".
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Old 04-20-2015, 09:26 AM   #6
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Quote:
Originally Posted by B3NN3TT View Post
This is my formula, using the average speed for the tank:.... The equation goes like this:
(your average speed) - 21 = X
X 27 = your highway percentage
100 - (your highway percentage) = your city percentage
It's still a subjective number.....
Yeah, subjective & not accurate! I drive slow(love my beautiful Washington state & drive to see it....longer), even on the highway(60-65, while others drive 85mph & often on back country roads(35-50mph). By your equation, almost 50% of my driving is city, & that ain't true.
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Old 04-20-2015, 10:08 AM   #7
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Quote:
Originally Posted by litesong View Post
Yeah, subjective & not accurate! I drive slow(love my beautiful Washington state & drive to see it....longer), even on the highway(60-65, while others drive 85mph & often on back country roads(35-50mph). By your equation, almost 50% of my driving is city, & that ain't true.
That's the point of this entire thread: "Accurate" itself is entirely subjective, and there is no wrong way to do it; only what works for you personally.

"City" and "Highway", in this instance, aren't referring to geography, by the way.

My commute is 100% on city streets; stop-and-go traffic. The car rarely sees an actual "highway" in the regular parlance of the word. Yet my average speed is usually several ticks over the lowest average speed threshold because I drive enthusiastically and use the explosive nature of my vehicles to their greatest effect.

The formula is consistent and repeatable, and no guesswork is involved on my part. So that's why I use it.
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Old 04-20-2015, 12:10 PM   #8
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This has the details on the various test cycles for the EPA test.
Detailed Test Information

The city and highway cycles are still the two main tests, and haven't change since they were introduced. They yield high mpg results in line with what the NEDC and Japanese test cycles report. That figure is used for CAFE requirements.

The three new ones are used to come up with a modifier to adjust those results down to what consumers see on the window sticker. Which works better than the flat modifier that was used in the past. If they are used. Right now, a manufacturer can elect to skip those tests and come up with a modifier mathmatically. That appears to work fine for the typical American car sold, but overestimates for hybrids, turbos for economy, and other high mpg cars.

Mainly, I posted this for people to see how, um, laid back and easy going the test routes are. Most of us would quickly get annoyed driving behind such a person. Then most roads among the suburbs, that many may think of as city because of the lower speeds, would actually be highway under the test.

I estimate my route at 33% city. It could less than that, but I'm taking the lower speeds and increased stops from traffic into account.
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