Emergency Stop--How far?

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Emergency Stop--How far?

July 31, 2011, 10:58:09 am

Has anyone gone out and attempted to determine how far their coach travels after they hit the brakes hard? With the weights the coaches weigh today I think we might be underestimating our stopping distance and possibly following too close. I realize that if we back off an appropriate distance about five idiots will pull in front of you, but what the hey. Better safe than sorry. We did an emergency stop so we would have an idea of how far it goes after hitting the brakes. No, we did not measure the distance. Just wanted a feel for how far.

Re: Emergency Stop--How far?

Reply #1 – July 31, 2011, 11:48:46 am

I think you have hit on the main issue of trying to leave a safe and appropriate distance between our large vehicles and folks ahead of us. It seems that no matter how hard I work to achieve the "5 second" stopping cushion, there are always nitwits who see that as an invitation to jump right in and cut my stopping distance in half(or more). You just have to be ready and always have "Plan B" in mind, I guess.

Re: Emergency Stop--How far?

Reply #2 – July 31, 2011, 12:17:14 pm

This is one of the reasons I travel slower than the speed limit on the Interstates. I rarely do not have a large distance between me and the vehicle in front of me. I also do not see it as a safety issue.

Re: Emergency Stop--How far?

Reply #3 – July 31, 2011, 01:14:30 pm

Yes on the long distance, going slower, and plan B. I try to keep a LONG distance between us and the vehicle in front - I don't like to think about what we would do to a small car. I try to keep up with the oncoming traffic, the emergency lane and what is beyond emergency lane. I think I would choose a fence and field over hitting a car in front of me. I haven't been given the choice yet, fortunately.

oldMattB

Re: Emergency Stop--How far?

Reply #4 – July 31, 2011, 03:11:27 pm

Rough rule from the old DDC classes for the Nat'l Safety Council is 4 seconds from the vehicle in front of you in a truck or MH ( 2 seconds in a car ). Not always easy to do, that is one reason I stick at 5 or so below the limit on major highways. that way they are always passing me and its easier to adjust following distance. I love it when a car passes me going like h.... and then I see him at the next gas station while I roll on.
Gary B

Re: Emergency Stop--How far?

Reply #5 – July 31, 2011, 05:38:33 pm

Jeff and Carol can verify that I am a bit of a lead foot, however I have found a new speed that I like. The last two trips on the interstate I have stayed at 59 mph. Being 1 mph slower than the governed trucks means that everyone pretty much passes me and if someone pulls in front of me, they pull away rather than make me slow down. I hope I can stay with this speed. It certainly will save fuel and makes the trip more relaxing.

Time will tell.

Re: Emergency Stop--How far?

Reply #6 – July 31, 2011, 08:29:27 pm

Nitehawk: At some point 3-6 years ago on the old forum, some member posted his experience with the braking portion of a safety inspection required in his state (California?). Told us about the speed required before applying brakes, and the minimum distance required for stopping once brakes were applied. Don't remember the metrics (and I have searched unsuccessfully for the post), but I do remember his report that when he applied full panic stop capabilities (instant full retarder, instant full brake, simultaneously), he beat the minimum standard big time.

FWIW. I like your "getting a feel for" approach. Experiencial learning accumulates over time, and increases the likelihood that your anticipation of need to apply slowing/stopping responses, and your performance of them, will become more intuitive, automatic, and correct when situations require them. And... having good objective data to feed the rational part of learning and performance will keep it all tethered to objective reality. Good combination. Be interesting to see if others already have some numbers or standards.

Kent: I've been driving pretty close to your "new speed" for several years now, for the same reason, and get the same result. Most of the time, I have plenty of open road in front of me. On open freeways, that is. Even works to a degree in high traffic areas, especially if I can get the middle of three lanes. But you already know this.

Re: Emergency Stop--How far?

Reply #7 – July 31, 2011, 08:39:14 pm

I'd have to travel in 5th gear to stay at 59. 60.5 is as slow as I can travel in 6th.

Re: Emergency Stop--How far?

Reply #8 – July 31, 2011, 10:38:27 pm

But the question is, "Will you get better mpg at 59 or 69.5?" You might be surprised On Jul 31, 2011 5:39 PM, "amos.harrison" <amos.harrison@yahoo.com> wrote:

Quote

I'd have to travel in 5th gear to stay at 59. 60.5 is as slow as I can travel in 6th.

Re: Emergency Stop--How far?

Reply #9 – July 31, 2011, 11:29:26 pm

Another reason I love my 400 ISL. Goes into 6th gear around 54 I think. Personally, I favor traveling in the range between 59 and 62, no matter what the speed limit...especially when towing. Just not in that big of a hurry anymore with a motorhome.

I only had to "panic stop" my old 1990 U280 once, and was very surprised and pleased at the performance of those 4-wheel disks. I certainly agree that we should have a good feel for what distance we can accomplish when throwing out the anchor in a hurry.

I'm so used to using the retarder, that after a trip, it takes me a long time to stop hitting the Acura MDX's armrest panel, expecting the retarder joystick to slow me down.

Re: Emergency Stop--How far?

Reply #10 – August 01, 2011, 01:22:34 am

Your air brake pedal assembly has a spring in it to provide resistance and give the pedal "feel". Anyone who has used a steering column air brake lever can remember how easy it is to just pull the lever back and give full air application. Good idea to make some fairly fast stops at city and highway speeds to see what it feels like and see how hard you have to push down on the pedal. Make slower speeds stops first and avoid lockup.

Following distances should be very conservative, especially for new owners. With a high driving position like a GV, you are going faster (and take longer to stop) than you think. In the rain, best to be really conservative and extend following distances, especially with first rain of season. Watch speeds on wide boulevards with 45 mph limit and occasional traffic lights. Easy to misjudge speed and end up in an intersection (or worse) when the light goes red.

On newer fire apparatus, I could easily lockup all six with moderate pressure. Had to make almost max effort stops perhaps 5 or 6 times in a couple of minutes on a lot of calls when approaching red lights.

At the top of a really steep downgrade, I usually glance at the air pressure, just in case.

Like I said in the past, don't plan on to much from the parking brake if you use it in an emergency. Very lengthly stop at highway speeds on the flat and if heading down a steep grade, well...

Our four speed shifts at 48 mph so can't enjoy anything slower without it shifting down to third. With or w/o toad, I like 58 to 62 also. Gets better mileage too and have learned to relax and watch the countryside go by.

Re: Emergency Stop--How far?

Reply #11 – August 01, 2011, 07:03:15 am

The trolley air valve on side of steering column only operates the trailer brakes, not sure in a fire truck if they have the same valve.
Can assure you today a trucker making too many panic /near max stops, will have the insurance company having them terminated pronto. The lil computer will tell all, even the panic stops, too many and your history. Picture a company and the average panic stop numbers show an average of 2 per month, now you have hot rod Joe, making 2 or more a day average, the insurance will have him terminated pronto. Reason, the driver is too aggressive and needs to seek employment else where.
These ECM boxes on these new engines are capable of a lot more info than we like to know or be reminded of.

Re: Emergency Stop--How far?

Reply #12 – August 01, 2011, 07:45:31 am

After years of riding motorcycles I carry the same attitude and attentiveness when in our GV: In an accident--I lose; Always drive where I can see the other driver--never get in his "blind" spot; Intersections are especially dangerous--cross traffic & especially after the first rain after a dry spell--the road has more oil drippings and diesel residue on it making it slippier. The deposits on the road are greater at intersections due to vehicles having to sit & wait for lights to change or cross traffic.
It is bad enough that a panic stop has to be done, but distance is compromised if at an intersection. Unfortunately a lot of drivers need to relearn their stopping capabilities after the first rain or snowstorm. It is always possible to start fast but stopping takes longer with poor equipment such as bald tires, bad brakes, inclement weather.

Re: Emergency Stop--How far?

Reply #13 – August 01, 2011, 08:41:23 am

Its important to remember that people will do amazingly stupid things to not get 'stuck' behind you.

Re: Emergency Stop--How far?

Reply #14 – August 01, 2011, 09:36:48 am

AND,,,ALWAYS Remember to stow all loose items, they become projectiles.

Re: Emergency Stop--How far?

Reply #15 – August 01, 2011, 10:35:58 am

Another BIGGIE, Anytime you hit the rear of a vehicle with the front of your vehicle, you are GUILTY, It does not matter what fire truck or rescue squad vehicle your driving. You gotta know your limits and the limits of what ever your driving.

It would take a smart lawyer and stupid judge to convict the victim in the front vehicle that got rear ended by a fire truck, but stupid things happen everyday.

Re: Emergency Stop--How far?

Reply #16 – August 01, 2011, 11:30:28 am

Dave,

Absolutely correct on both counts. Even if we went into a intersection code three, had an accident and the court found we were even 10% at fault = big payout from city. In an older city with obstructed views of intersections, a red light meant 35 to almost 0 each time the light was against us so the brakes got a workout on each call. In other words for those who remember, a real "E" ride. Max throttle to 35 after clearing the intersection until repeated at the next block. Older districts of many cities are difficult as streets were built for traffic 80 years ago.

A lot of these calls were with Crown or Mack apparatus with non-syncro crash boxes so the word quickly got around who could dbl clutch and make glass smooth down and up shifts without clicking a gear and those who searched fruitlessly for the next gear until the rig stopped. Dave, your MCI was a crash box, right? Are you "Cool Hand Luke" or a searcher?

Yes, the trolley valve only operates the rear brakes. Was just comparing being able to pull it back to get max air application without much effort with a couple of fingers (does have a very light spring so it returns) compared to a lot of pressure against the spring on the foot valve. As you are aware but others may not be, the hand valve is used after uphill stops (with a manual transmission) so the apparatus does not roll back when letting out the clutch.

The engine right in front of me went through a stop sign code three and hit an ambulance traveling at least 65 mph (coming from our left). The ambulance put down skid marks over 260 feet and even though traveling 30 mph over the limit for responding emergency vehicles on city streets, the ambulance company won the court case.

Never really had to worry about rear ending someone as we had to stop well behind the car in front so we could pull out in case of a dispatch. I was on three big crashes responding, never as a driver but sitting backwards in the jump seat. They all hit right below my feet.

Re: Emergency Stop--How far?

Reply #17 – August 01, 2011, 11:54:28 am

Between the retarder and disc brakes all around, my FT stops faster than expected in a panic stop. Much faster. I had a traffic light turn red at exactly the wrong time on a highway. I was traveling at 60MPH, and had to apply full braking to stop before the limit line. Everything not bolted down slid forward, and the deceleration felt harder than under similar circumstances in a car. It was a good thing I didn't have a truck or SOB motorhome on my tail.

Re: Emergency Stop--How far?

Reply #18 – August 01, 2011, 12:22:16 pm

Pierce,
I am laughing indeed, and do understand. For the MCI, you bet it came with a 4 speed Spicer crash box, hated every part of it, why within 2 months I changed it over to a RT910 RR, that makes everyone look like an old hand, but using the clutch was a no no once you got moving. The big issue to make the conversion from the Spicer to the RR, was the engine, The way Greyhound/MCI spec'd the 8V-71 was unusual in that the flywheel housing was a SAE 1, however the flywheel was a SAE 2. Now that becomes an educational issue to retro fit a standard transmission,
Installed the proper flywheel SAE 1, and double disk clutch assy, then when trying to bolt up the SAE 1 transmission housing, the depth of input shaft too long by 1/2". So back to changing the transmission nose from SAE 1 to SAE 2, getting an adaptor ring from Mack, that goes between a SAE 1 bell housing and a SAE 2 transmission. This was the only way the 1/2" spacing worked out. Now that was all correct, it is time to figure out the shifting setup. standard MCI shifting is two push/pull rods. could not see an acceptable way of making that work nicely. So went to KW and bought the COE new style cable shifter with two cables to the new adapter on the RR, required 2 Morse cables 33 ' long. When all complete, it shifted better than a COE, and nearly as good as a Conventional..
Why I say that with a welder, grinder, drill and a little moxie, you can make anything. Of course a lathe and a Bridgeport can be an advantage too.
Engines course later

Re: Emergency Stop--How far?

Reply #19 – August 01, 2011, 01:47:14 pm

I'm impressed. A lot of people talk but... If I leave anything out, you catch it. One of those things only lots of experience can do.

My 4107 was the hardest thing to shift perfectly, No tachometer and with the engine at the back, it was hard to exactly time the shifts plus no compound low and a tall reverse that used first gear for it.

Have driven cable shift cars but not rigs.

Will have to talk one day.

Re: Emergency Stop--How far?

Reply #20 – August 02, 2011, 05:29:09 pm

Tom Lang said it well. With the retarder on, full braking stops the FT well. I don't know distances. I have had one "opportunity" to stop fast when a car pulled in front just as a light turned. The FT stopped shorter than I thought it would, and I'm very pleased. It stopped about 12 to 15 feet shorter than I expected, and saved me from hitting the car that jumped in front of me. I keep the retarder on in the city.

Re: Emergency Stop--How far?

Reply #21 – August 02, 2011, 08:10:44 pm

I have to agree. Last fall a road obstacle in front of us caused everyone to come to an emergency stop. I thought sure we would hit the car in front of us but thankfully, no the Foretravel did its job. I did have towed brakes installed that week. I figured you only get a few free lessons. You better pay attention when you get one.

I am now very glad we got the M-G towed brakes. They make smooth regular stops much easier and I am sure will be beneficial in an emergency.

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