[Archived]

Tom has nailed it and just to add another real life example, 2 people are now dead in Knoxville as of a Friday afternoon accident on I-40.

We won’t know if the accident was their fault or if the truck that hit them was tailgating, but the deceased were in a small pickup like a Chevy S10. Traffic ahead came to a rapid stop. The truck slammed into the S10 and it in turn was pushed into an SUV at which point if appears the big truck went over the rear crushing the S-10.

It could have been the S10 pulled in front of the truck taking away his stopping distance or the truck was tailgating or the driver was distracted. But the bottom line is the smaller vehicles stopped much quicker than the large truck.

We can expect to need 290 feet to come to a stop from 60 MPH. The average car will require 120 feet. The stopping distances are based on our buses being at the axle weight limits. If we exceed those limits the distances can be expected to be greater. Our brakes suck. It takes a very heavy application of brake to extract maximum performance so as Tom says give it a try so you understand how difficult it is to do a panic stop.

For those of you that like to drive faster, the stopping distance is substantially greater. Increase your speed by only 10 MPH to 70 and you need an additional 150 feet to get stopped. 450 feet more or less total stopping distance from 70 MPH. So when you are in rush hour traffic and the space between vehicles is small and you are doing 70 make sure as Tom says that you always have a plan. I exercise my neck trying to keep track of everything around me in the morros of both sides just in case I have to jump over a lane to avoid a collision.

[Michael]

Tom Did you spin your Prevost 360 and were ok ?/

[Glenn]

Here’s an article on Phase I and Phase II upgrades to FMVSS 121 which governs heavy vehicle stopping performance.

The new standard, effective Aug, 2013, puts an upper limit of 250′ from 60 mph on the most common tractor trailure configurations which populate our highways. It’s interesting that vendors can attain this performance with simple upgrades to existing drum brake technology. Disc brakes bring these stopping distances way down with a safety margin of from 10 to 30%. Imagine stopping your bus in 180′. I haven’t been able to find any third party testing of modern day Prevost coaches but I’d bet they can stop well short of 250′ from 60 mph, fully loaded. The transmission retarder adds yet additional stopping power. In search of a deserted highway! 🙂

Not to downplay the seriousness of this issue; simply fascinated with the technology. We’re still way short of the typical automobile stopping performance. The answer is to always choose the lane that gives you the most stopping distance, be vigilant, maintain suitable traffic gaps, watch your speed, and maintain your equipment.

[Archived]

Cars travel in “packs” as we know, so stay in the “pocket”
and you will be much safer. Paying attention to what’s behind you is just as
important as what’s in front or passing you. I had two separate issues with a
truck and a RV blowing out tires in front of me recently. I had plenty of
distance to slow down and avoid any problems only because I was in the pocket
well behind them. I have noticed that safe drivers run just below the speed limit so as to
have the traffic “flow” around them. That way is safer I think because people
seem to pay more attention while they are passing you as to when you are next
to them driving the same speed. Train yourself to be omni- present and all is
well.

Fred

[Archived]

David,

From driving semis I can tell you the braking on my bus sucks compared to the stopping distance of a semi. We have a number of folks very familiar with semis on PC and maybe they will add to this discussion, but while we may be able to beat the standard my guess is the margin is slim. But no matter how well our coaches stop, compared to the average car we still need a lot of distance.

[Archived]

A great thread for sure, Tom I had the same thing happen to me on I-77. We had stopped for lunch at a Cracker Barrel when we started to get on I-77 again I could not get in the right lane because a kid was texting and did not see me beside him. When he looked up and saw me he immediatly turned the steering wheel a left 90 degrees with out looking to see if any thing was in the passing lane, thank goodness, because he also did a 360 and hit the cable guard rail and then that sling shoted him across both lanes and he too ended up in the ditch, probably pissed his pants too! This could have been a 5-6 car and bus pile up! No one was hurt, thank goodness Can’t believe people text and drive, Gary

[Archived]

Here’s an Altoona STURRA test report for a 2012 Prevost X3-45. Loaded to GVW of 47110 lbs, dry payment, average of 4 runs at each speed, no retarder, they report the below stopping distance data. For each speed I calculated the deceleration rate using: a = V*V/2*d. Using 16.38 ft/s2 as the deceleration rate, an extrapolation shows a stop from 60 mph would require 236 feet. Roughly two times what a typical car can do. I’d expect this number to improve somewhat with a transmission retarder.

20 mph: 304 ft: 14.32 ft/s2 deceleration

30 mph: 59.77 ft: 16.20 ft/s2

40 mph: 103.70 ft: 16.60 ft/s2

45 mph: 132.94 ft: 16.38 ft/s2

No point, just interesting info. 🙂

[Charles]

The Bendix Brake certification class spends time viewing videos of braking tests. During the class which concentrates on semis we were shown how certain factors influence braking, such as ABS. There were no surprises except how an ABS equipped trailer outperformed a non-ABS trailer combination by a wide margin.

The eye opener was how much the braking distance increased from 60 to 70. If viewing that video did not make a driver slow down, nothing will. New standards either now in effect or close to going in effect are going to bring stopping distances down by a significant amount. I cannot remember the reduction, thinking it might be under 200 feet for a stop from 60, but the point the instructor made was securing loads on trucks meeting the new standards is now a serious problem. That of course affects us. I have had hard stops and heard the glassware banging together and plumber’s putty unable to stop stuff from tipping over.

The point is shorter stopping distances are going to help us a whole lot, but when we get there securing stuff in the coach is going to become a very serious issue.

[Archived]

I am in a 99 KW grossing 72,000 today, and can guarantee I can get this rig stopped faster than the Prevost Royale. Before owning the coach, Jon had told me about the braking….I am still shocked at the braking distance and how much more aware and proactive I have to be when driving it. And yes, keep a constant eye on your mirrors for escape routes. Oh, by the way, this Cat powered truck has 1,405,000 miles on her, one rebuild.

[Archived]

Kicking that Cat and walking that Dog.