Go Back   EcoModder Forum > EcoModding > Hypermiling / EcoDriver's Ed
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 12-22-2007, 10:21 AM   #1 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,530

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 62.14 mpg (US)
Thanks: 4,078
Thanked 6,978 Times in 3,613 Posts
Technique quandary: gliding toward a stale green light - to pulse or not to pulse?



A hypothetical, hair-splitting, nit-picking technique question, inspired by Newton's thread - Idea for government: Traffic Light Timers

Here's the hypothetical situation (OK, this actually came up for me last week). What would you do - assuming your goal is maximum fuel economy?

The scenario:

You're alone in your lane (nobody close behind), in a med/low speed glide approaching a stale green light which does NOT have a pedestrian count-down timer, or even a walk/don't walk signal.

You think the light is controlled by sensors for cross traffic. There's a vehicle on the sensor. In other words, the light may change at any second, but you can't predict when with any certainty.

Your options:

1) throw in another pulse as you approach the light, and hope you make it through on green;

2) continue gliding down, considering that if you don't pulse, you'll more or less roll to a stop at the light (which may still be green when you get there);

3) some other option?

__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 12-22-2007, 11:02 AM   #2 (permalink)
igo
Master EcoModder
 
igo's Avatar
 
Join Date: Dec 2007
Location: Wheeling, WV
Posts: 410

Mini Box Truck - '05 Scion Xb
90 day: 32.87 mpg (US)

It FITs - '09 Honda Fit Sport
90 day: 36.2 mpg (US)

Impreza - '13 Subaru Impreza Sport
90 day: 30.92 mpg (US)
Thanks: 12
Thanked 14 Times in 10 Posts
Well, I would go for it and run the light with one or 2 seconds of red if I had to, but I am usually in a bit of a hurry.

Gliding down probably would be better for the mpg.
  Reply With Quote
Old 12-22-2007, 01:51 PM   #3 (permalink)
Dartmouth 2010
 
SVOboy's Avatar
 
Join Date: Nov 2007
Location: Hanover, NH
Posts: 6,447

Vegan Powa! - '91 Honda CRX DX
Team Honda
90 day: 66.52 mpg (US)
Thanks: 92
Thanked 122 Times in 90 Posts
Send a message via AIM to SVOboy Send a message via MSN to SVOboy Send a message via Yahoo to SVOboy
I would prolly do a glide down and not worry too much about it, Usually sensor activated lights change pretty quickly around here.
  Reply With Quote
Old 12-22-2007, 05:47 PM   #4 (permalink)
Master EcoModder
 
Peakster's Avatar
 
Join Date: Dec 2007
Location: Regina SK Canada
Posts: 407

Red Jeep Patriot - '07 Jeep Patriot
90 day: 25.14 mpg (US)

Beige Ford Ranger - '95 Ford Ranger XLE
Thanks: 0
Thanked 2 Times in 2 Posts
I'd continue coasting to the light if no one is behind me. Bummer that the scenario has a car already at the light. At nighttime, without any cars at a camera-sensored intersection, I usually flash my high-beams on and off a few times as I approach the traffic light as that often makes the light turn green in my city.

EDIT: oh! you mean the light is green already for me and the car ahead is cross traffic. Sorry my bad.

Yeah, I'd definitely pulse to try and beat the light.

Last edited by Peakster; 12-22-2007 at 05:51 PM..
  Reply With Quote
Old 12-22-2007, 05:49 PM   #5 (permalink)
EcoModding Apprentice
 
Join Date: Dec 2007
Location: Melbourne
Posts: 152

The Mighty Mira - '92 Daihatsu Mira
90 day: 61.32 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
That's a tough one... the ratio in fuel wasted is:

Vspeed up^2:Voriginal^2

Often you are going 50kph or so, and you might have the choice of speeding up to 60kph. So that's 36:25 ratio, not a lot of difference, but if you gamble and lose, you pay even more. And if your car is anemically powered, the gamble is not a good one at the best of times.

If you could only hear me curse in the instances where I have gambled on a speed up and lost!
__________________
"Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed." - Isaac Newton
  Reply With Quote
Old 12-23-2007, 02:25 AM   #6 (permalink)
EPA MPG #'s Slayer
 
diamondlarry's Avatar
 
Join Date: Dec 2007
Location: Elkhart, IN
Posts: 32

La Forge - '07 Toyota Prius
90 day: 84.38 mpg (US)

DOHCtor Green MPG - '99 Saturn SL2
90 day: 49.17 mpg (US)

Silver Sipper - '00 Honda Insight
Thanks: 2
Thanked 0 Times in 0 Posts
On stale green lights, I always assume they will be red and keep gliding. I won't pulse again until I reach a point where it is certain that I will make it through on the green, ie, as I'm entering the intersection.
__________________
  Reply With Quote
Old 12-23-2007, 02:12 PM   #7 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,530

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 62.14 mpg (US)
Thanks: 4,078
Thanked 6,978 Times in 3,613 Posts
Quote:
Originally Posted by newtonsfirstlaw View Post
but if you gamble and lose, you pay even more
There's the key point.

If you throw in another pulse, and the light does in fact change to red, you're forced to brake (or run it, if you're igo ) - and probably brake pretty hard. Gas in --> brake dust out = FE nightmare.

If you keep gliding and the light does in fact change to red, you're far better off than if you had pulsed & braked (since in this scenario, I mentioned you would pretty much coast to a stop at the intersection anyway).

I really did face this situation a few drives back. As it turned out, the light *didn't* change to red on the approach, so I ended up re-applying power just as I got to the intersection (having almost coasted down to zero).

It's a completely bizarre, non-intuitive tactic to use. Green means go, right? Yet there I was, coasting nearly to a stop facing of a green light (NOTE! Not affecting any other drivers.) But if max mpg is the goal, only a predictable green means go.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 12-23-2007, 10:03 PM   #8 (permalink)
Giant Moving Eco-Wall
 
DifferentPointofView's Avatar
 
Join Date: Dec 2007
Location: The Dale, IL (or A-Dale)
Posts: 1,120

The Jeep! - '95 Jeep Grand Cherokee ZJ Laredo
90 day: 23.75 mpg (US)

The Caliber - '07 Dodge Caliber R/T
90 day: 30.6 mpg (US)

The 'Scort - '98 Ford Escort LX
Thanks: 0
Thanked 7 Times in 6 Posts
I know this has nothing to do with this pulse and glide thing, but it does have to do with traffic lights, Does anyone have trouble seeing the new LED lights?(i think they're LED). I am red/green color blind, which makes red and green colors kinda slewed and discolored, so I occasionally think that darker greens are browns and darker reds are browns, reds look pinkish and greens look yellowed. I can still see green and red, I'm just missing cones in my eyes, which makes colors not what they normally are.

When the wind is blowing the new traffic lights, I can't see them until I'm right under them because they concentrate the light in a straight line, which is bad when it's busy or dark and busy. They might think that it is new and helpful, but one of these days I'm either gonna get a ticket for running a red light, or I'm gonna smash into another car.
__________________


Yea.. I drive a Jeep and I'm on a fuel economy site, but you just wouldn't understand... "It's a Jeep thing!" *Jeep Wave*

Did I Use Too Many Abbreviations? Here's The Abbreviations List
  Reply With Quote
Old 12-24-2007, 12:49 AM   #9 (permalink)
Awesomeness personified
 
AndrewJ's Avatar
 
Join Date: Dec 2007
Location: Columbia, MO
Posts: 642

Harold - '94 Honda Civic CX
90 day: 54.51 mpg (US)

Margot - '08 Surly Big Dummy
Thanks: 0
Thanked 28 Times in 18 Posts
Send a message via AIM to AndrewJ
Where I am there are a lot of lights that are "lensed" so that you can't see the green light until you're 50-80 meters from the intersection. I have noticed that in most cases the red light is not "lensed" so you at least have something to judge the color of the light.
__________________
"I got 350 heads on a 305 engine. I get 10 miles to the gallon. I ain't got no good intentions." - The Drive By Truckers.

  Reply With Quote
Old 12-29-2007, 02:01 PM   #10 (permalink)
Master EcoModder
 
metroschultz's Avatar
 
Join Date: Dec 2007
Location: Norfolk, Va. USA
Posts: 869

CPT SLO - '93 GEO Metro plainjane
90 day: 53.91 mpg (US)

SilverHairBeauty - '01 Toyota Avalon XL
90 day: 24.06 mpg (US)
Thanks: 14
Thanked 33 Times in 28 Posts
Send a message via AIM to metroschultz
A fellow color blind driver, kudos to you for keeping you license. I just look at the location of the light. Green always on bottom. Red always on top. And I coast to the lights as much as possible. Safety first and sometimes heavy traffic won't let me P&G. S.

__________________


When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity.
Albert Einstein
  Reply With Quote
Reply  Post New Thread






Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com