Out of gear coasting safety

[tasdrouille]

It is often argued that out of gear coasting, be it in neutral or with the engine off, is dangerous, and even illegal in some places.

Why is that exactly? I have a hard time figuring that out.

The main argument I heard is that you are SOL if sudden acceleration is needed as an evasive maneuver. When exactly do you need to "accelerate suddenly as an evasive maneuver"? You might need to getting out of a driveway crossing oncoming traffic, but that's not quite a situation where you would be coasting. I tried to ask myself this question in a coasting situation, and I wasn't able to find any.

[MazdaMatt]

coasting up to a light I regularly have @$$holes in huge trucks trying to wipe the dirt off my hatch with their headlights. If he was sipping a coffee, its time for "evassive acceleration". The right move is often the gas pedal. Hit black ice? get on the gas in a FWD and you'd straighten out. (its a hard lesson to learn, but while regularly pushing the limits in my track car, i have learned that point and shoot gets you out of any oversteer conditions)

[MetroMPG]

I don't believe I've ever had to use the accelerator to get out of trouble. Then again, I can't recall the last time I had a close call either.

I believe the main concerns against engine-off coasting are:

1) the loss of power assist in cars equipped with power steering. Of course we all know you can still steer, but steering effort can increase dramatically depending on the system's design.

2) potentially overheating the brakes on a long descent (where engine braking could take some load off the braking system)

3) potential loss of vacuum assist in cars with power brakes (I've recently been in two older vehicles whose brake vacuum "leaks" away, even with no pedal application. My car seems to hold a reserve for a long time after the engine has been shut off). And of course we all know you can still brake without vacuum assist, but the pedal effort can go up a lot, depending on the car.

[MazdaMatt]

Also, at a stop light if the guy behind you loses his brakes or is out to lunch, or is scolding the children in the back of her suv and doesn't see the light. I stare in my rear-view when I'm at a stop. Never know... that's why I'd rather idle at a stop light if there is any traffic. Saving gas should never trump saving your @ss

Steering is definately a major concern. My car is TOUGH to steer without power assist.

[dcb]

It's often another excuse not to do anything different. 99.999999... percent of accidents are caused by people using too much acceleration. My car/bike starts in an instant if I need it to.

[MazdaMatt]

Lets have a race... we'll get an suv to roll up on us from behind. I'll drop my clutch and you depress yours, put it in gear, start your car and then go... we'll see who gets hit.

I believe that you are completly wrong in your assumption. Now, I'm not going to go looking for data, but I have read that MOST accidents are single-car, and MOST multi-car are rear-enders. Why don't people get out of the way of those rear-endings?

[NeilBlanchard]

Hello,

To the OP's question -- there is a huge difference between coasting in neutral with the engine idling, and EOC.

IMO, costing in neutral with the engine idling presents zero safety issues, if you are driving the way you should -- i.e. keeping an eye on what is going on all around you.

EOC, in my car at least presents a serious challenge to maintaining control (both steering and braking are very difficult), and so for me, EOC does present a large increase in risk.

[dcb]

Just FYI, it has presented no serious challenges in any of my vehicles. The brake reserve is manageable, in fact I haven't bothered to reconnect the vacuum on the metro and I have much better feel on the brakes now, and most of my fleet are manual steering. The ones that aren't are not that challenging to steer with any amount of forward motion. Your mileage may vary, try it in a safe spot for yourself before making excuses. It is not an absolute to say it is unsafe, it depends on the car and on the driver, and should be weighed against all other unsafe activities on the road before deciding this needs serious attention.

Matt, FYI, I can't read your posts, in case you weren't aware.

[MazdaMatt]

dcb smells... haha... he can't read this

I wonder how he knew I was posting.

Anywho... if you have a manual rack and you're used to no-vac brakes, then there is not really any danger except for at or approaching a stop in a heavy-traffic area. If you are not used to non-boosted brakes or your car has a highly-assisted steering rack like mine, don't do it unless it is a long empty downhill freeway with no crossroads.

[PaleMelanesian]

There is one case I've been in. Stopped, waiting to make a left turn across traffic, from a major street onto a side street. Driver behind didn't seem to notice brake lights AND turn signal. A quick acceleration avoided a rear-ender. Now I leave it running and ready in those situations.

Any other time I'm stopped and engine-off, I'm in first with the clutch pedal depressed. It's a quick crank-release to move.

[tasdrouille]

If power assist was the reason eocing is dangerous then power assist would be mandatory on all vehicles.

The potential rear-ending accident example presented earlier would not be caused by coasting per se, but by the driver not being aware of his surroundings and driving accordingly.

I got rear-ended once, there was traffic ahead and the guy behind me wasn't looking when I braked. I am pretty sure most rear-ending accidents happen when there is a sudden change in the speed differential between 2 vehicles following each other. A situation that hardly ever happen when coasting out of gear.

[PaleMelanesian]

Ah, I see. You're talking about coasting more than stopped engine-off.

It's a design decision, but my Odyssey has lead-weight heavy steering without the assist. My civic, on the other hand, is barely any different. If the van was designed differently, it could be (nearly) as easy as the civic.

[texanidiot25]

Originally Posted by MazdaMatt

Also, at a stop light if the guy behind you loses his brakes or is out to lunch, or is scolding the children in the back of her suv and doesn't see the light. I stare in my rear-view when I'm at a stop. Never know... that's why I'd rather idle at a stop light if there is any traffic. Saving gas should never trump saving your @ss

Steering is definately a major concern. My car is TOUGH to steer without power assist.

That's how my dad avoided a large multi-car rear endings. When he was dating my mom back in HS. '74 Camaro, big block 396, regular bracket racer. One day, he up and ran a red light, and my mom was furious as to why. Turns out a medium duty truck rear ended a car 2 cars back, and pushed a few cars into the intersection.

In traffic I don't engine brake or sit in N (auto), too much going on around me. But engine off is entirely out of the question on my car. I've been in it when it's stalled out mid turn, no bueno with no power steering.

[i_am_socket]

Steering my car is no biggie without power, just takes actual force of hand+arm instead of 1 finger. Braking is something that I won't try at anything > 15 mph without vacuum. I may do the extended vacuum canister mod at some point.

From N to D while engine on in my auto tranny = .5 seconds and i'm out of there if need be.

[cfg83]

tasdrouille -

Originally Posted by tasdrouille

It is often argued that out of gear coasting, be it in neutral or with the engine off, is dangerous, and even illegal in some places.

Why is that exactly? I have a hard time figuring that out.

The main argument I heard is that you are SOL if sudden acceleration is needed as an evasive maneuver. When exactly do you need to "accelerate suddenly as an evasive maneuver"? You might need to getting out of a driveway crossing oncoming traffic, but that's not quite a situation where you would be coasting. I tried to ask myself this question in a coasting situation, and I wasn't able to find any.

Here's my take. In the not so long-ago past, cars had lousy brakes. Trucks going downhill could become runaways without in-gear engine braking. Sooooo, laws requiring cars to always be in gear made sense. Cars of today are better, and almost all have power steering/brakes as standard. From my POV, the answer always depends on these three things :

Power Steering : If you have a light car like my Saturn, which was offered without power steering in it's base configuration, then a power steering delete can negate that issue.

Power Brakes : As we have seen in other threads, you can augment your power brakes with additional home made or aftermarket vacuum canisters.

Driving Context : This is the biggest issue, IMO. If you live in a rural area, you can use EOffC much more because traffic density is so much lower. If you live in urban areas, EOffC opportunities are few and far between. In a manual transmission, I do think you can get away with EOnC, because you have to physically downshift to initiate emergency acceleration anyway.

CarloSW2

[greenitup]

i don't try and take any sharp turns with the engine off.
i drive a truck and can easily steer it and stop it with no power, and i'm not extremely strong. My brakes last long enough to when i turn it back on. If i park on top of a hill and coast down to the stopsign then brake then coast to the next one and stop, then start it takes alot of work to stop it but is feasable.

[trikkonceptz]

I believe what people need to do is argue that EOC is dangerous in their situation because ...


I find myself Eocing and automatic for distances up to 3/4 of a mile, its what my commute allows, I usually am never on the brake until the last 500 feet or so, my biggest heart skip is starting the engine while the car is still rolling, that creeps me out.

Now as far as the rear end scenario, I guess I grew up differently, that means the driver behind you is at fault and I automatically see body mods and vehicle improvement when something like that occurs.

So with enough of us on here now it would be an interesting statistic to chart.... Accidents CAUSED by Ecomodding, my guess is it will be a short list ...

[MetroMPG]

Texanidiot: good story. Your dad's really on the ball if he's that aware of what's going on in traffic behind him. I used to teach rear crash avoidance as part of a defensive driving curriculum. Most are entirely avoidable. But most people don't pay attention to what's happening behind them.

Originally Posted by tasdrouille

If power assist was the reason eocing is dangerous then power assist would be mandatory on all vehicles.

Not when you consider that a manual rack has a different steering ratio than a power assisted rack. So when the assist goes away, it's harder to steer that car than the equivalent one with manual steering.

I'm obviously playing devil's advocate. I EOC in all kinds of cars, with some variation based on a vehicle's steering effort without assist.

But I'd prefer that people are fully aware of the consequences of losing assist in both steering & braking before startling themselves (and others?) because they attempt the technique in traffic without practicing it first. Unfortunately, I've read a couple of posts here and elsewhere of people doing just that.

[dcb]

Playing the Devils nemesis, my wife can EOC all around town and back into the garage on a power steering car with the engine off without any problem.

But yes, practice in a safe place, make sure you can still control the vehicle. You are responsible for not running into other people/things.

[azraelswrd]

Since I started HM, I've been more aware of my rear primarily to avoid slowing down traffic and to prevent potential tailgaters from forming. Since calibrating the SG and my MPG numbers are more realistic I've been using NICE-On more often but just not comfortable using it with company or at very high speeds. I only do it at night with next to zero traffic and on straightaways.