Advice on rolling stops or full stops

[redpoint5]

What I hate is 4-way stops that have a dominant street of travel. These should be 2-way stop with the dominant street not having to stop at all.

For that matter, all left hand turns should be yield instead of force you to wait for a protected turn.

If people weren't morons we'd all be able to move along more efficiently, both time-wise, and in fuel.

[prr]

Some good thoughts to chew on. What is nagging at me is the 1/1000 chance that when I roll through a stop, there will be a cop looking at me. And yes a single ticket is going to wipe out years and years and years of MPG saved by these rolling stops.... to say nothing of the 1/1,000,000 chance of hitting someone because out of habit I rolled through a stop sign and didn't see them. I think for my own money, as well as greatly diminishing the chances of getting into an accident, I'll re-learn the habit of stopping at stop signs.

[redpoint5]

A lifetime of rolling through stops will never save enough money in fuel to cover the cost of a single ticket. If rolling through a stop at say 1 MPH saves a puny amount of fuel, then rolling through at 55 MPH saves a ton. So we've got to decide on how fast we should blow through a stop to save fuel. It seems to me that speed should probably just be zero since that is the law, and you're just increasing risk from any point above that.

[D.O.G.]

Originally Posted by redpoint5

Unless your rolling stop is at 15 miles per hour, it's not going to save that much fuel.

Although I'd put the minimum speed lower, I agree that the savings are too small to notice over a full tank.

Only you can decide if your particular stop sign is safe (or not) to creep through. I always come to a full stop at one particular stop sign but only sometimes at another.

[jcp123]

I basically have to make full stops in my Honda, because its cold idle is kinda stupid. Once warmed, though, I either try to avoid stop signs, or only aim for a Hollywood stop if it's an uphill launch. Old Hondas like mine could probably be out-torqued by a bicycle, I still have trouble doing an uphill launch from rest.

I got popped for a Hollywood stop a few years ago. The fine wasn't huge, but why get a ticket when you don't need to?

[Fat Charlie]

Like most other things in life, everything else in driving and multiplied by hypermiling, you have to pay attention and you ought to be fine. If spotting the car/pedestrian/camera that will issue the ticket takes too much of your attention, it's not worth doing whatever you need to watch out for. So don't do it. I play it conservatively, I'll even bump start before I go past a cruiser.

[Vman455]

We can simplify this problem a bit and attach some actual numbers using the Work-Kinetic Energy Theorem to get a general idea if it's worth rolling through or not. Assuming a weight of 1850 kg (the lightest trim of the 2006 Highlander Hybrid, yours may actually be heavier), a speed limit of 25 mph (11.1 m/s), and a difference of 0 mph (full stop) versus 1 mph (0.444 m/s rolling through):

Work (W) = Kf - Ki
K = (1/2)mv^2
Kf = (1/2)(1850 kg)(11.1 m/s)^2 = 113969.25 J = 114 kJ
Ki,rolling = (1/2)(1850 kg)(0.444 m/s)^2 = 182.3508 J = 0.182 kJ
Ki,stop = (1/2)(1850)(0 m/s)^2 = 0 kJ

Wrolling = 114 kJ - 0.182 kJ = 113.818 kJ = 114 kJ
Wstop = 114 kJ - 0 kJ = 114 kJ

So you can see, the difference is within rounding error to 3 significant figures. However, that 0.182 kJ does equal 0.05056 Wh, out of 33.1 kWh in one gallon of gasoline--or 0.0000015% of a gallon. You would need to roll through approximately 654,725 stop signs at 1 mph to save one gallon of gas, and that's assuming 100% conversion efficiency.

There are much easier, legal ways to save one gallon.

[fusion210]

Originally Posted by Vman455

We can simplify this problem a bit and attach some actual numbers using the Work-Kinetic Energy Theorem to get a general idea if it's worth rolling through or not. Assuming a weight of 1850 kg (the lightest trim of the 2006 Highlander Hybrid, yours may actually be heavier), a speed limit of 25 mph (11.1 m/s), and a difference of 0 mph (full stop) versus 1 mph (0.444 m/s rolling through):

Work (W) = Kf - Ki
K = (1/2)mv^2
Kf = (1/2)(1850 kg)(11.1 m/s)^2 = 113969.25 J = 114 kJ
Ki,rolling = (1/2)(1850 kg)(0.444 m/s)^2 = 182.3508 J = 0.182 kJ
Ki,stop = (1/2)(1850)(0 m/s)^2 = 0 kJ

Wrolling = 114 kJ - 0.182 kJ = 113.818 kJ = 114 kJ
Wstop = 114 kJ - 0 kJ = 114 kJ

So you can see, the difference is within rounding error to 3 significant figures. However, that 0.182 kJ does equal 0.05056 Wh, out of 33.1 kWh in one gallon of gasoline--or 0.0000015% of a gallon. You would need to roll through approximately 654,725 stop signs at 1 mph to save one gallon of gas, and that's assuming 100% conversion efficiency.

There are much easier, legal ways to save one gallon.

That's pretty amazing as my answer was going to be full stop with traffic or not great visibility, but mostly 1-2 mph.

[slowmover]

“Never idle, and never stop” is the mantra for metro driving.

But it isn’t literal. It means (after having cut out ALL unnecessary cold starts and combined ALL errands) to study

Best Routing

Which isn’t necessarily shortest in time or distance.

The ideal route MAXIMIZES steady-state.

THEN one studies the route more closely. This includes traffic control devices. Knowing where they are to, again, maximize off-throttle glides to a stop.

The habit of disobeying devices will sooner or later backfire. With the possibility of a t-bone accident, your life or others is in jeopardy.

So . . there are full stops AND there are full HARD stops.

Remember that with a stop sign one must be aware of the intersection entrance. To fully stop well behind that (I know you’re a bad driver when you encroach the intersection ). It’s also a tactic to get rolling ahead of the guy from another direction. Which may not be important very often.

So it isn’t about stopping or not, it’s about total versus lesser vehicle momentum loss. And that’s by examining details.

Frankly, the best route won’t be improved by evading TC devices. Wrong place for a margin, plus enormous penalty.

A stop is like a turn. One must enter & exit well. The speed thru the turn or the exact full stop made isn’t to the point.
.

[redpoint5]

You're better off beginning a coast to a stop sooner to save fuel than simply rolling through.

There's a stop sign nearby where I live, and a slight downhill to it for about 1/3 mile. I'll start coasting from the crest of that hill, adjusting my last speed input based on the traffic I see ahead. A wide gap will develop between me and the person ahead and sometimes traffic will begin to bunch up behind me. By the time I coast to the intersection, the guy in front of me is just accelerating from his stop, and I'm right behind. The perfect coast, having wasted no fuel and having delayed nobody. Often though, there's nobody behind me because prior to the coasting straight is twisting roads, and I don't slow for twists.