Driven to Save -- Opinions Needed! (hypermiling book author seeking feedback)

[TEiN]

From the Manual on Uniform Traffic Control Devices (MUTCD), U.S. Department of Transportation, Federal Highway Administration, page 451:


B. Steady yellow signal indications shall have the following meanings:
1. Vehicular traffic facing a steady CIRCULAR YELLOW signal indication is thereby warned that the related green movement or the related flashing arrow movement is being terminated or that a steady red signal indication will be displayed immediately thereafter when vehicular traffic shall not enter the intersection. The rules set forth concerning vehicular operation under the movement(s) being terminated shall continue to apply while the steady CIRCULAR YELLOW signal indication is displayed.



Further down:

Section 4D.26 Yellow Change and Red Clearance Intervals
Standard: (page 485)

The exclusive function of the yellow change interval shall be to warn traffic of an impending change in the right-of-way assignment.
The duration of the yellow change interval shall be determined using engineering practices.

...

Guidance:
14 A yellow change interval should have a minimum duration of 3 seconds and a maximum duration of 6 seconds. The longer intervals should be reserved for use on approaches with higher speeds.

[Tango Charlie]

I think we're all saying pretty much the same thing about the yellow light, so I hope we're not getting hung up on semantics. I will say this, though; I will speed up a bit (not a lot) if I catch a yellow in a series of lights, to avoid catching the next one or two yellow.
And then on the other hand, I don't think we need to be encouraging anyone to breeze through yellows, do we? It's pretty much standard proceedure; we do it (if we can do it safely) to save momentum and improve our fuel economy, and Joe Public does it because he's late for work.

[TEiN]

TC,

The point of the post was not to get hung up on semantics, but to add a bit of official information as to the question of the meaning of yellow: does it mean "stop", or does it mean "clear the intersection, a red light is impending"?

[jamesqf]

Originally Posted by MetroMPG

If I have to speed up to avoid catching the red, I probably could have stopped (assuming no tailgater). Maybe the amber lights are longer around here?

Could be. I know that around here, they sure aren't long enough to always stop safely - which doesn't mean a panic stop ending in the crosswalk with dog, groceries, and driver pressed against the windshield.

On some of the larger roads (with 50+ mph speed limits), they've started putting in advance warning lights a hundred yards or so from the intersection, that come on a few seconds before the yellow.

[MetroMPG]

In the section Braking: Or Lack Thereof, various scenarios about anticipating slowdowns/stops ahead in traffic are laid out, with lots of attention to timing traffic lights.

The idea that the (friction) brakes are your enemy is made (and made, and made again ).

But there's an advanced technique where the brake pedal IS your friend, and it's not mentioned: There are times when it pays to brake early in order to scrub enough speed so you can now coast along at a lower speed / longer duration than you otherwise would have been able to if you had only coasted.

EG: say you're faced with a stale red light where you could do a considerable amount of coasting, then lightly brake at the end to finally come to stop at the stop line. You could do that.... OR you could do some early braking to scrub some speed, with the result that you can now coast for longer, at a slower speed, and you reach the intersection still moving when the light changes.

In other words:

Option #1): Coast first, light brake to a stop.
Option #2): Brake first, coast at a lower speed, and preserve momentum so you avoid having to stop.

Or, I could have pointed to tip # 49 on our driving tips list.

[MetroMPG]

Oh, this occurred to me too:

At one point, the brake is referred to -- among many other names -- as "the cursed middle pedal".

There is a very large chunk of the North American driving population that will be confused by the "middle" description.

[Sven7]

Middle? What? I drive an Apple iCar and it only has one pedal!



:P (all my cars have three pedals)

[Diesel_Dave]

Originally Posted by MetroMPG

In the section Braking: Or Lack Thereof, various scenarios about anticipating slowdowns/stops ahead in traffic are laid out, with lots of attention to timing traffic lights.

The idea that the (friction) brakes are your enemy is made (and made, and made again ).

But there's an advanced technique where the brake pedal IS your friend, and it's not mentioned: There are times when it pays to brake early in order to scrub enough speed so you can now coast along at a lower speed / longer duration than you otherwise would have been able to if you had only coasted.

EG: say you're faced with a stale red light where you could do a considerable amount of coasting, then lightly brake at the end to finally come to stop at the stop line. You could do that.... OR you could do some early braking to scrub some speed, with the result that you can now coast for longer, at a slower speed, and you reach the intersection still moving when the light changes.

In other words:

Option #1): Coast first, light brake to a stop.
Option #2): Brake first, coast at a lower speed, and preserve momentum so you avoid having to stop.

Or, I could have pointed to tip # 49 on our driving tips list.

Very good point. I do this all the time. I think of it as "damage control". Ideally, you shouldn't have had to brake at all, but, if the lights turned on you unexpectedly, the goal then becomes to pass through the light at the maximum possible speed (i.e., scrub as little of your speed off as possible).

[MetroMPG]

Damage control is a good way to describe it. Sometimes things happen without warning though, and not every road gives a clear sightline to the next traffic light!

----

In the section Horsepower and Torque – Pull Hard, Pull Fast ...

Torque is how much force your engine exerts each time the crankshaft turns

Some smarter people than me will probably challenge this description of torque!

[user removed]

Originally Posted by MetroMPG

Damage control is a good way to describe it. Sometimes things happen without warning though, and not every road gives a clear sightline to the next traffic light!

----

In the section Horsepower and Torque – Pull Hard, Pull Fast ...

Some smarter people than me will probably challenge this description of torque!

Also a good time to crank the AC up to max and use the wasted energy to get your evaporator cool, then use the fan and recirculate to keep the cool air coming after you have shut off the compressor. Call it free regenerative AC, using inertia otherwise lost. In a manual you can downshift and keep the compressor pumping even in DFCO.

regards
Mech