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.