Motorcycle USA Forums : Join the Revolution
  HomeLog InRegisterCommunity CalendarSearch the ForumHelp
   
Motorcycle Message Board - Motorcycle USA > MotorcycleUSA.com! > Motorcycle Safety > The Safe Stopping Distance Rule  Forum Quick Jump
 
You cannot post new topics in this forum. You cannot reply to topics in this forum. Printable Version
32 posts in this thread.
Viewing Page :
 1  2 
[ | Show Newest Post First ]

DataDan
Rodent Of Unusual Size



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Sep 2003
Total Posts : 1054
 
   Posted 3/13/2007 9:22 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

The Safe Stopping Distance Rule requires that you be able to stop in the distance you can see to be clear. If you can’t, you’re just throwing the dice.

Here’s a scary conclusion from Harry Hurt’s study of motorcycle crashes: "The typical motorcycle accident allows the motorcyclist just less than 2 seconds to complete all collision avoidance action."

Sounds hopeless, doesn’t it? You’re riding along, taking reasonable care, then a hazard pops up out of nowhere, and 2 seconds later you’re chewing the pavement. But that stat doesn’t tell us how the rider got into a spot where the potential hazard went unseen until just 2 seconds before impact.

Another finding from Hurt suggests what leads up to that kind of situation: "The view of the motorcycle or the other vehicle involved in the accident is limited by glare or obstructed by other vehicles in almost half of the multiple vehicle accidents." Stationary objects such as buildings contributed too. Visual obstructions not only reduce the time available for the rider to react to a hazard, but also limit the view from other drivers to the motorcycle. By recognizing the potential danger, a rider can use speed and position to give himself the time he needs to deal with unseen hazards.

In an example of a crash preceded by an obstructed sightline (see first photo attached), a northbound 51-year-old rider on a Harley rounded the bend at the big tree and saw a log truck making a left turn from the side road on the right at the top of the photo. Unable to stop, the rider skidded and crashed before sliding into the truck. As the rider passed the tree, the intersection and the truck would have been visible 300 feet ahead. At 60mph, a good rider should have been able to come to a stop before reaching the intersection, but this rider couldn’t. Maybe he was going faster than that (the report doesn’t say), or maybe his braking skills were poor. And even if the truck driver began his turn before the motorcycle became visible around the bend, the truck wouldn’t clear the northbound lane in time to avoid the motorcycle at 60mph.

A second example occurred at the Y intersection in the second photo attached. A 21-year-old rider on a Honda CBR600 was traveling northeast, "way over [the speed limit of] 35" according to a witness, as a bus crossed the intersection from the north to the parking lot on the south. The rider was unable to stop and hit the bus at considerable speed. Because of the building on the northwest corner, the bus stopped at the intersection would become visible to the rider—and vice-versa—at a distance of 200 feet. At 35mph, he could easily come to a stop in time to avoid the bus, but if he were going significantly faster, he could not. And if the rider were at a higher speed, the bus couldn’t clear the intersection in time to avoid the motorcycle even if the driver saw the roadway to be clear when she began to cross.

In both examples, regardless of legal fault, the rider could have prevented the crash by following one simple rule: Never ride so fast that you cannot stop comfortably on your own side of the road within the distance you can see to be clear. That’s one of the guiding principles taught to British police riders, and it can serve all riders equally well.


A superior rider uses superior judgment to avoid problems that would demand his superior skill.

Post Edited (DataDan) : 5/4/2010 10:54:22 PM GMT


Image Attachment :
Image Preview
photo1.JPG
  100KB (image/pjpeg)
This image has been viewed 385 time(s).
Image Attachment :
Image Preview
photo2.JPG
  55KB (image/pjpeg)
This image has been viewed 419 time(s).
Back to Top
 

YellowDuck
Registered Member



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2003
Total Posts : 4130
 
   Posted 3/13/2007 9:31 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

Yep.

I started a thread here about five years ago called "spring tooth culivator".  It was about the mental image I used to convince myself not to over-ride my sightlines.

It's basically a bit of worse-case scenario imagery to keep me focused on safety.  A spring tooth cultivator is a piece of agricultural equipment, with a bunch of curved, heavy metal tines mounted to a massive metal frame.  When folded for transport, the tines point straight up, but the whole rig might be only three feet tall, and wide enough to cover a bit more than one lane of traffic.

So, while rounding a bend or cresting a hill, I would think about whether or not I could stop in time if such a thing were sitting in my lane.  Not stopping successfully would mean being launched at best, and neatly eviscerated at worst.

That thought usually got me to slow down.

 



Cynicism is what passes for insight among the mediocre - Joe Klein

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 3/13/2007 10:32 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Over the years I have actively tried to increase my following distance to nothing less than the 2-second minimum, and more whenever I can. I think this makes a HUGE difference. Yet, I'd say more than 75% of cycle riders follow other traffic more in the 1 second or perhaps even .5 second range for highway speeds. At 60 mph, that's from 22 to 44 feet behind another vehicle. I don't care how good your vision is, or how quick your reactions are, when you're that close you CANNOT react adequately and correctly for the situation.

60 mph equals 88 feet per second of distance covered. Average reaction time (before you even touch the brakes) is .5 second.
So if a bike is 30 feet behind a car (pretty common around here), the car and traffic are blocking the rider's view going forward, and the car passes over a truck muffler laid sideway in the lane, the rider may try to apply maximum braking. But, he won't even have the brakes on until 44 feet AFTER the car has passed the muffler. Thats brakes applied 14 feet PAST the muffler.

Or, say the car driver suddenly sees the muffler and goes bonzo nuts on the brakes. The bike rider reacts, .5" second AFTER the car's brake lights come on, and very likely slams into the back of the car before the brakes on the bike are really applied enough to slow it down.

Back off riders!!! Too many of you follow WAY to close. That includes you retired couples riding in going out for dinner shorts and short-sleeves (no helmets or riding gear) on your shiny Gold Wing, you leather clad Harley custom riders (with the skinny front tire and one front disc brake), you young new riders on a clapped out mid 80's Gixxer (brake fluid hasn't been changed since 1985), you returned riders on new BMWs with all the right gear, you commuters trying to save gas riding to work on late 70's UJMs. I have seen so many riders doing it, that it is a class-less mistake made by all types of riders.

Another thing I have noticed about many riders, over the years in teaching the MSF courses, that most riders only squeeze the front brake lever to a "comfort" point of stopping and figure that's good enough. Well, its not. Unfortunately, the very moment these riders need every bit of braking capability is usually when the events cause a major panic reaction and they either severely under-brake and hit what they want to miss, or massively over-brake and loose control. This is one of the main reasons to practice braking to get very comfortable with your braking ability. Thanks Dan!


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Back to Top
 

Candy750
06 Shadow Aero



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Aug 2006
Total Posts : 1217
 
   Posted 3/13/2007 12:48 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Good points to consider.

I periodically review plans submitted for road construction in housing developments (PUD), more often, I review appeals to the planning boards for the approval of the housing development where existing roads already are. These reports show the site distance for curves, intersections, etc. and speed limit on that road - and the correlation of both in consideration of traffic and safety for the PUDs. Often, studies of traffic are included, which will show that the average actual speed of traffic is lower than the actual posted speed on the roads.

That makes me think. Even though the posted speed limit is 55, the planning board approves roads and hazzards at an at least slightly reduced speed. Also, the yellow triangle shaped signs that "suggest" a speed for a curve (say 35 mph even tho 55 is the posted speed limit) were likely also decided and posted using data that studied slightly slower moving vehicles on that road....

So, while it seems to me the universe of riders and drivers say that "5 to 10" over the speed limit is "not" speeding, in fact, it is.

(and that's my public serivce announcement for the slow....)


 
Candy 
---------------------
Honda Shadow 750 Aero
Candy Dark Red

Back to Top
 

Smitty
Registered Member

Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2003
Total Posts : 22123
 
   Posted 3/13/2007 1:32 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
When you are in terrain you are not familiar with THEN for sure you slow down your pace compared to speeds in roads you use time & time again.  You have to be really on your toes to stay alive when riding a m/c be it your terrian or new areas.
 
Many things can & do distract people like in some cases at night I notice red lights & wonder if it is a vehicle, accident scene, or whatever, but no it is a neon sign indicating the price of petrol & some distance ahead on this bend or it could be a restaurant.
 
One chap openly admitted he was passing a large building to notice himself like a mirror on their windows & reason he had said accident.  Young chap sort of admiring himself on his m/c, so you do have to wonder about difference in what we see & our minds.


Remember all the others on the road are crazy & out to kill you.

Post Edited (Smitty) : 3/15/2007 5:54:57 AM GMT

Back to Top
 

louemc
Registered Member



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2003
Total Posts : 17483
 
   Posted 3/13/2007 1:37 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy VH said...
Over the years I have actively tried to increase my following distance to nothing less than the 2-second minimum, and more whenever I can. I think this makes a HUGE difference. Yet, I'd say more than 75% of cycle riders follow other traffic more in the 1 second or perhaps even .5 second range for highway speeds. At 60 mph, that's from 22 to 44 feet behind another vehicle. I don't care how good your vision is, or how quick your reactions are, when you're that close you CANNOT react adequately and correctly for the situation.

60 mph equals 88 feet per second of distance covered. Average reaction time (before you even touch the brakes) is .5 second.
So if a bike is 30 feet behind a car (pretty common around here), the car and traffic are blocking the rider's view going forward, and the car passes over a truck muffler laid sideway in the lane, the rider may try to apply maximum braking. But, he won't even have the brakes on until 44 feet AFTER the car has passed the muffler. Thats brakes applied 14 feet PAST the muffler.

Or, say the car driver suddenly sees the muffler and goes bonzo nuts on the brakes. The bike rider reacts, .5" second AFTER the car's brake lights come on, and very likely slams into the back of the car before the brakes on the bike are really applied enough to slow it down.

Back off riders!!! Too many of you follow WAY to close. That includes you retired couples riding in going out for dinner shorts and short-sleeves (no helmets or riding gear) on your shiny Gold Wing, you leather clad Harley custom riders (with the skinny front tire and one front disc brake), you young new riders on a clapped out mid 80's Gixxer (brake fluid hasn't been changed since 1985), you returned riders on new BMWs with all the right gear, you commuters trying to save gas riding to work on late 70's UJMs. I have seen so many riders doing it, that it is a class-less mistake made by all types of riders.

Another thing I have noticed about many riders, over the years in teaching the MSF courses, that most riders only squeeze the front brake lever to a "comfort" point of stopping and figure that's good enough. Well, its not. Unfortunately, the very moment these riders need every bit of braking capability is usually when the events cause a major panic reaction and they either severely under-brake and hit what they want to miss, or massively over-brake and loose control. This is one of the main reasons to practice braking to get very comfortable with your braking ability. Thanks Dan!

 
Love the way you put it Andy,
Brings the conditions of reality into it. Just numbers of time and distance, doesn't include what makes it real.
Major difference is needed to accomodate the riders frame of mind. What this rider has been doing to be what they are.
A chowder head that is pre-occupied with whatever, and when the crisis comes, thinks it might be a good idea to do something if they only had some idea of what to do (it never came up before), doesn't fit in the same time/distance frame as someone that trail rode Dirt, just to have the fun, but something was going on in the brain. While reading the ground (trail or prefered line on a trail) as fast as can be managed, or rider that attended a track school or a few of them, and also chooses a max function featured race replica bike, because they know why the features are there. And rides the street/highway with that focused attention, is going to have two different outcomes to any situation.
 
I can't even read my own posts lol , but I know what I'm saying.   Wouldn't be surprised if no one else can smilewinkgrin


 Focus the forces, Be The Force

Back to Top
 

Well Enuff
--- Regaining my sanity --- one ride at time



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Jul 2006
Total Posts : 1925
 
   Posted 3/13/2007 9:55 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
YellowDuck said...

... A spring tooth cultivator is a piece of agricultural equipment, with a bunch of curved, heavy metal tines mounted to a massive metal frame.  When folded for transport, the tines point straight up, but the whole rig might be only three feet tall, and wide enough to cover a bit more than one lane of traffic.

So, while rounding a bend or cresting a hill, I would think about whether or not I could stop in time if such a thing were sitting in my lane.  Not stopping successfully would mean being launched at best, and neatly eviscerated at worst. ...


This very machine was used in the last scene of the movie The List of Adrian Messenger. It was used a murder weapon by hiding it behind a stone fence that was to be jumped by horse-mounted fox hunters.
 
A gruesome end indeed.


-- There is wrong in crime and fraud, somewhere.
-- Ignatius Donnelly 1831-1901

Back to Top
 

Well Enuff
--- Regaining my sanity --- one ride at time



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Jul 2006
Total Posts : 1925
 
   Posted 3/13/2007 10:09 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy VH said...
...
So if a bike is 30 feet behind a car (pretty common around here), the car and traffic are blocking the rider's view going forward, and the car passes over a truck muffler laid sideway in the lane, the rider may try to apply maximum braking. But, he won't even have the brakes on until 44 feet AFTER the car has passed the muffler. Thats brakes applied 14 feet PAST the muffler. ...
I learned this the hard but lucky way. I learned to ride sort of self-taught. That means I could start, stop and turn. But is sure didn't mean I could think. My roommate and I used to pull up near to the back of a semi trailer and draft. It was heaven doing over 60 mph at about half throttle on a 100cc bike with the wind at your back. nono  
 
One time as were  drafting southwest bound out of Daytona Beach I saw a pothole about 10 inches in diameter emerge from under the trailer right between our bikes! I pulled over to the side of the highway literally shaking. Red came back to me to find out what the heck was the matter.
 
I told him what I saw and that was the end of our drafting days. Ever since I have been a religious believer and follower of the 2 second rule.
 
Sometimes luck overcome stupidity to save unworthy souls like me. I pass this along to help repay the forces that prolong my survival.


-- There is wrong in crime and fraud, somewhere.
-- Ignatius Donnelly 1831-1901

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 3/14/2007 5:01 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Stories like yours, WellEnuf, are exactly why we, the "old timers" on this forum try to persuade all the newer in inexperienced riders with our advice. Its mostly because we have done enough stupid and wrong stuff in our riding history that we are so thankful to still be riding today. We know what we got away with, but we want to be sure others don't try some of the stuff we did get away with.

Now, what you report was something done of a concious choice. I can understand the thrill of doing that I guess. And even when you did it you must have realized some aspect of danger related to it. But what I caution about following to close is that these cyclists just figure this is normal riding for them, nothing will happen, all is good. I have seen riders following SO close, with their feet hanging way out there on the highway pegs, left hand on the hip. Think that might extend your reaction time by say, maybe a second? Many times this is on a bike with less than stellar brakes too yet!

Again, many, many riders never think about what could/can/will happen, until it does.


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Back to Top
 

HogWild
Registered Member

Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Oct 2006
Total Posts : 5123
 
   Posted 3/14/2007 9:05 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy VH said...
Stories like yours, WellEnuf, are exactly why we, the "old timers" on this forum try to persuade all the newer in inexperienced riders with our advice. Its mostly because we have done enough stupid and wrong stuff in our riding history that we are so thankful to still be riding today. We know what we got away with, but we want to be sure others don't try some of the stuff we did get away with.

Now, what you report was something done of a concious choice. I can understand the thrill of doing that I guess. And even when you did it you must have realized some aspect of danger related to it. But what I caution about following to close is that these cyclists just figure this is normal riding for them, nothing will happen, all is good. I have seen riders following SO close, with their feet hanging way out there on the highway pegs, left hand on the hip. Think that might extend your reaction time by say, maybe a second? Many times this is on a bike with less than stellar brakes too yet!

Again, many, many riders never think about what could/can/will happen, until it does.


Unfortunately when it does happen it generally hurts...... south central Kentucky and north central Tennessee have got to be the tailgate capitol of the world and bump drafting is the norm. That's one reason I stay off the super slab around here and use the backroads..... Ya just can't have enough of a safety zone with them idiots.....
Back to Top
 

RedDog
Retired SportBike Bum



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2003
Total Posts : 13635
 
   Posted 3/14/2007 9:48 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Here is the recipe HogWild ...

Get yourself a SPORTBike! Then you can ride around them LMAO!


RedDog
Think Ahead! Travel Light & Leave Your Fears Behind You!
Normal People Scare me!

Back to Top
 

HogWild
Registered Member

Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Oct 2006
Total Posts : 5123
 
   Posted 3/15/2007 7:07 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
RedDog said...
Here is the recipe HogWild ...

Get yourself a SPORTBike! Then you can ride around them LMAO!


I like the backroads option better and besides, I get to see more lol
Back to Top
 

RedDog
Retired SportBike Bum



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2003
Total Posts : 13635
 
   Posted 3/16/2007 6:43 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
You got a point. Sometimes wife drives, a car, and I sit and look at all the stuff I never saw.


RedDog
Think Ahead! Travel Light & Leave Your Fears Behind You!
Normal People Scare me!

Back to Top
 

DataDan
Rodent Of Unusual Size



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Sep 2003
Total Posts : 1054
 
   Posted 5/4/2010 2:49 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

A major drawback to the rule stated in my OP is judging stopping distance. Until you've accumulated a lot of riding experience, you're probably not going to be able to judge stopping distance from an arbitrary speed. To overcome that, I propose another way to judge safe speed for the available sight distance:

Maintain speed that allows you to see the roadway at least 4 seconds ahead.

The 4-second sightline interval is what MSF calls your "immediate path of travel." If an obstacle appears 4 seconds ahead, you'll have just enough road to brake to a stop before you reach it. But if you fly into a blind turn with less sight distance and there's a fallen tree in the road just beyond your view, you're probably going to hit it.

Note that this isn't the same as the 2-second following distance rule taught by MSF. The 2-second rule gives you time to react to when a vehicle ahead moving at the same speed as you brakes unexpectedly. The 4-second rule applies to the road itself, and it gives you the distance you need to avoid an obstacle that comes into view.

You probably know how to count a time interval from MSF: Spot a point in the road ahead and count out loud, "one one-thousand, two one-thousand,..." until you reach that point. But it isn't necessary to continually count out the sightline interval. With practice, you will quickly develop a sense for it so you can see the interval at a glance. On a straight, vacant stretch of road, take a guess at a 4-second interval and count it out. Adjust your guess and repeat until you've got it right. I've found that once acquired, the sense of it sticks permanently, though it's reassuring to calibrate it occasionally.
 
A few notes on the use of the rule:
  • While 4 seconds is a good rule of thumb, it's not enough at higher speeds. Over 80mph add 1 second. Over 100mph, you're on your own.

  • At speeds below 40mph, a 3-second interval gives you adequate braking distance.

  • The 4-second interval is valid if you're good on the brakes and the surface is clean and dry. If you're new, if you don't regularly practice hard braking, or if the road is wet, add 1 second. If you're a riding god capable of MotoGP-caliber braking even in an emergency, you can subtract a half-second.

  • The rule tells you not only when to slow down, it also helps you identify spots where higher speed may be possible. Other considerations will limit speed, but at least the sightline interval will tell you if you have enough braking distance.

  • The rule is usually easy to follow because you'll often have much more than 4 seconds. Coming on to a quarter-mile straight at 60mph you'll have 15 seconds of sight distance. Where the rule can save you is in a situation like cresting a hill or approaching a blind curve. When the sightline drops below 4 seconds, it's telling you that you don't have enough information to continue at that speed. Slow down to a speed that gives you that interval.

This table shows how the 4-Second Rule, combined with normal braking skill, gives you the space you need to brake for an unpleasant surprise.

The 4-Second Sightline Rule

 

speed (mph)

speed
(feet per second)

sightline interval (seconds)

sight distance (feet)

reaction
time

braking distance available

braking performance required (ft/sec^2)

30

44

2

88

1

44

22

 

3

132

88

11

 

4

176

132

7

 

 

 

 

 

 

 

 

 

40

59

2

117

1

59

29

 

3

176

117

15

 

4

235

176

10

 

 

 

 

 

 

 

 

 

50

73

2

147

1

73

37

 

3

220

147

18

 

4

293

220

12

 

 

 

 

 

 

 

 

 

60

88

2

176

1

88

44

 

3

264

176

22

 

4

352

264

15

 

 

 

 

 

 

 

 

 

70

103

2

205

1

103

51

 

3

308

205

26

 

4

411

308

17

braking below MSF standard

MSF to moto-LEO braking

superior to unattainable braking

For example, from 60mph with a 4-second sightline interval and 1 second reaction time, you will have 264 feet to stop. That can be achieved with deceleration of 15 feet/second^2. But with a 2-second interval, you will have only 88 feet to stop, requiring deceleration of 44 feet/second^2. Because the deceleration values are meaningless without context, the colors show the level of the braking they represent.

  • Green indicates less braking force than required for a satisfactory score on the MSF test. The 4-second rule tries to keep braking in this range. You can probably brake much harder, but that extra skill is kept in reserve for when your 4-second interval has tightened up to 3 seconds, when it takes more than 1 second to react to a hazard that surprises you, or when surface conditions limit grip.

  • Yellow indicates braking force that ranges from a top MSF score up to the standard that motorcycle LEOs must meet. You can probably brake in this range, but if you often rely on this level of skill for dealing with an unseen hazard, you'll have no reserve left for the unexpected.

  • Red indicates braking performance that starts at a level very few riders can achieve in a street-riding emergency and ranges up to rates that a street motorcycle simply isn't capable of. If you need to brake this hard to avoid an obstacle, you're most likely going to hit it.

Following the 4-Second Rule doesn't mean spoiling your fun by riding around at warning-sign speeds all day. In many turns, you have a sightline interval greater than 4 seconds even at truly stupid speeds. There the limits are your skill and the motorcycle's capabilities. The rule kicks in only when the sightline shortens and the danger from an unseen threat increases. So it shows you both where unknowns set the limit and where you are constrained by the limits of your own abilities.

The 4-Second Rule isn't an absolute. Experienced riders with many thousands of miles adjust speed to the situation without this rule or any other; it eventually becomes an automatic decision. But while you're gaining the experience needed to develop that intuitive judgment, it's nice to have an easy-to-follow rule of thumb to help you out. 


A superior rider uses superior judgment to avoid problems that would demand his superior skill.

Post Edited (DataDan) : 5/5/2010 6:16:44 PM GMT

Back to Top
 

PowerG
Registered Member

Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2006
Total Posts : 1248
 
   Posted 5/4/2010 5:46 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I reckon so LOL. What is the absolute deceleration capability threshold for the average bike? 33 ft per sec/per sec would be roughly neg 1g... From looking at braking tests on a few different bikes anything over 30 is approaching the limits of some of the better stopping bikes available, with expert riders aboard, on test surfaces. I saw a test of police bikes somewhere on the net somewhere a while back of a couple of HD's and a BMW police bike, and all three models tested in the 28-29 range.

Practicing emergency stopping is paramount to making this work, you need to know not only how fast you can slow it down but also how much is too much. The time to perfect keeping a wheel from locking up isn't when you're about to hit the garbage truck.


2007 V-Star 1300 

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 5/5/2010 6:43 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Excellant addition Dan! Based on what I observe of many, many riders, they are typically riding well into the RED zone quite often. And quite often they are following behind other vehicle with HALF the distance you show for the read zone. Its little wonder we don't have more crashes around here. Some riders claim to have excellant reaction time, which may be true, but unless you learn and practice your high effort braking skills, reaction time means little if anything.

On top of that, I bet that well less than half of cycle riders NEVER do any high effort braking practice. Plus they have no odea what the bike can do, and more importantly what they themselves can and cannot do. But once you test your braking skills and practice your skills, you realize what space you need to have reasonable stopping distance, then you'll adjust your following distance to suit. Not only that, but as you increase your following distance, you are even LESS likely to need to perform high effort braking.


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 5/8/2010 4:06 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Today after working at the BMW dealership I decided to go out and do some high effort braking tests. I chose a smooth clean rural rode with clear sightlines and power poles along the road to act as my braking start marker. I'd get up to speed, approx 60 mph, when I got alongside a chosen start marker, I'd apply the brakes with quick increasing effort until I stopped. With the bike stopped, I'd walk back from the leading point of the front tire back to the start marker (granted this is all approximate, but I repeated it a bunch of times).

For this test, I wasn't concerned about enagaging the ABS, so my brake lever/pedal effort was high enough to actuate the ABS system (I know it did, because I could hear the ABS pump working). During braking I could feel the bike squirm a bit as I stopped, but it stopped straight each time. After I stopped, I paced off and counted my steps back to the start point. Looking back to the bike I could see a definite tire stripe leading all the way back to the front tire. After about eight attempts at this I counted from 36 to about 42 strides. Each stride, for me I have a 30" inseam, is about 34".

Average number of strides = 39, times 34" per stride = 1,326", divide by 12" = 110.5'
If I estimate my stride at 36", and figure 42 strides, that still = 1,512", divide by 12" = 126'
So, referencing this chart of braking distances I found online:
Speed Braking distance
90 MPH 300 feet
80 MPH 238 feet
70 MPH 182 feet
60 MPH 134 feet (this is a decel rate over 29 ft-sec-sec, VERY high effort braking)
50 MPH 93 feet
40 MPH 59 feet
30 MPH 33 feet
20 MPH 15 feet (the old MSF standard for 20 mph is 23 ft, so this a high effort stop)
10 MPH 4 feet
Given these distances, the braking rate per this chart is very high. Consider that at 60 mph the decel rate is 29 ft/sec/sec. The rate of gravity is 33 ft/sec/sec, so this rate is .89 G-Force, pretty high.  

Given that, and considering for error, and estimation, I bet I am in the range for 60 mph. But I am not satified that I am measuring anything accurately. Because right now it looks like I am some hyper/uber-braker nearing 1-G stopping force. Uh,...ego aside, I don't think so. So tomorrow I'm taking this a step further and measuring my distance with a 150' tape, and from a consistent braking marker. I will also count my strides per the measured distance to see if I have any accuracy with the test today. Plus I'll take photos to document the event. I'll attempt 10 stops for better data and see how I measure up. My bet is my braking distance is more like 150' from 60 mph. MORE TO COME!


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Post Edited (Andy VH) : 5/9/2010 12:10:55 AM GMT

Back to Top
 

DataDan
Rodent Of Unusual Size



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Sep 2003
Total Posts : 1054
 
   Posted 5/8/2010 5:47 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

I'm really interested in what you find with more precise measurement, Andy.

In this comparison of ABS and non-ABS bikes (done by US DOT and Transport Canada--link is to a PDF of the report at msf-usa.org), the BMW R1150R stopped at .96g with ABS activated. Also, MCN reports identical stopping distance for the R1150R and the R1150RS (the bike you ride, IIRC). So, the measurement in your initial trial may be more accurate than you think.

FYI, in the table I posted above, I used 28ft/sec^2 as the upper limit of the yellow zone. This is equivalent to a 138ft stop from 60mph or a 62ft stop from 40mph. The latter is a testing standard I have seen for some police motorcyclists.


A superior rider uses superior judgment to avoid problems that would demand his superior skill.

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 5/8/2010 6:27 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Thanks Dan! I can say that after doing eight stops today, I could feel it head wise, as I had a bit of a headache (no kidding). I DO know that during each stop I could definitely feel it IN my head. Perhaps the G-load is higher than I am estimating. So the data I hope to gather tomorrow could be really interesting.

What was also interesting is during each stop I could feel the bike squirming and adjusting its tracking as I came to a stop. Also, each stop left a very definite stripe from the front tire on the pavement. This concurs with what I know about ABS systems, that ABS system effectiveness is based on the tires actually very slightly sliding for maximum braking and stability. That's why when a car does an ABS assisted stop, you WILL hear tire squealling and see tire tracks on the pavement. So I'll take pictures to show the tracks.

By the way, prior to this test, my front brakes had developed slight noise during braking. I knew I needed to deglaze the brakes, which is actually why I went out to do some braking practice in the first place. Now my brakes are quiet again, so I know I scuffed off the glazing on the brake pads with repeated high effort stops. More results soon!


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Back to Top
 

PowerG
Registered Member

Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Mar 2006
Total Posts : 1248
 
   Posted 5/9/2010 9:24 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I practice stopping often, I have a road that is probably as good as most test pads near me that has a two mile sightline, newly paved, with a center line consisting of 12 ft stripes with 12 ft spaces between them. I have picked up two things that anyone who rides a cruiser needs to watch closely for-if you adjust the back brake too tightly, you're almost guaranteeing wheel lock on the rear. As the weight transfers it's going to require a lot of concentration and probably some modulating to keep that tire rolling. In a true emergency stop in traffic it would be quite easy to lock that tire up...it you keep the bike straight you can survive that, but anything deviating from a straight line is a low side waiting to happen. I have re-adjusted the rear brakes to compensate for this, a longer range of foot movement is required for general usage, but there's a little more leeway and feel in high effort stops. (I use the rear brake a lot, a leftover habit from dirt biking.) I continually advocate to the riders I know that they need to practice stopping so that what happens during a true emergency stop won't be something they're trying to learn how to control in what could be a life or death situation, but they usually kind of nod and insinuate "oh I think I can handle it". Well no, I think you probably can't, but that's something for you to decide.

The other problem isn't so easy to solve. I've noticed it in braking practice, and especially during the stop I had to make in traffic a few weeks ago posted elsewhere in which I bumped the rear of the cage. As the front tire loads and the angle of the bike changes the top of the windshield drops down also, as you're fighting your body's momentum to keep going as the bike stops, if you do happen to hit what you're trying to avoid at any significant speed you are going to hit that windshield, very possibly with your face. I am thinking wearing the FF more for this very reason.


2007 V-Star 1300 

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 5/10/2010 7:35 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Ok here are my results from my slightly more accurate braking test session. I set up a 150 foot braking lane out on a rural road, running east/west, measured with a long tape. The road was smooth, clean, grippy aged asphalt. After setting up my markers 150' apart, I paced off the distance to use as a reference from the bike to the marker when I stopped. The 150' distance took 53 strides, so that equaled 2.85' per stride. After each stop, I'd dismount and walk the number of strides to the ending brake marker. Only two of the 12 stops were slightly longer than the 150' braking lane.

I got my bike up to an indicated 65 mph, which I know on my bike is just slightly over 60 mph, and made sure the speed was steady before I got to the braking marker. At the marker I applied both brakes as best I could. I noted when the ABS activated, which was probably 75% of the 12 stops. Each stop left a very definite stripe from the front tire, but no lockup and sliding. I also noticed the bike squirmed around a bit but also self corrected. Here we go:
TEST DIRECTION DISTANCE SPEED (approx) NOTES
1 East 165.5 60 1st test and helped establish my marker start point
2 West 140.0 60
3 East 142.9 60
4 West 151.4 60
5 East 152.1 60 Definite ABS cycling of the rear brake, overbraking on rear
6 West 134.4 55 Speed was definitely lower at start of braking zone
7 East 154.2 60
8 West 150.0 60
9 East 141.5 60
10 West 141.5 60
11 East 157.7 60 Attempted stop with no ABS actuation
12 West 137.0 60
AVG 147.3 My speed was only estimated as read on speedometer

The tire marks on the pavement also helped me determine I was applying the brakes 12' to 21' before the brake start marker. I adjusted my noted stop distance by adding the early stop distance to the ending position. So even though this was all estimated, the repeated efforts and variables are minimal enough to determine some consistency. Some other notes, my bike has ABS, and a type of front suspension that has designed in limited squat during braking. No matter how hard I apply the brakes the steering geometry remains consistent which helps to control the bike. By the end of the testing I could sense a slight headache due to the G-loading of the stops.

When I compare these results with the chart listed earlier, I can say that chart is either very accurately compiled from lots of data and riders, or, I think, it is much too general and actually shows a better result than I think is real. Going back to my earlier "test", I found my results based on my measured strides, my paced off distances are very close to what I estimated, which correlates with my results for this test:

Average number of strides = 39, times 2.85' per stride = 111.2'
So that means my speed had to be lower than I thought to achieve that shorter result, more like 55 mph or lower. The final points are unless you test and practice your braking, you'll never know what you can safely achieve. So, for my average of 147' at 60 mph, if I add one second reaction/application time (88' for 60 mph) to a real world stop, my best average TOTAL stopping distance for 60 mph stops would be 235 feet!! Eye opening!


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Post Edited (Andy VH) : 5/11/2010 3:43:32 AM GMT


Image Attachment :
Image Preview
Brake test 001.jpg
  163KB (image/pjpeg)
This image has been viewed 390 time(s).
Image Attachment :
Image Preview
Brake test 011.jpg
  318KB (image/pjpeg)
This image has been viewed 402 time(s).
Image Attachment :
Image Preview
Brake test 005.jpg
  378KB (image/pjpeg)
This image has been viewed 650 time(s).
Back to Top
 

DataDan
Rodent Of Unusual Size



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Sep 2003
Total Posts : 1054
 
   Posted 5/10/2010 8:31 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

Thanks very much for doing that, Andy. Very interesting.

FYI, your average stopping distance of 147.3ft from 60mph is average deceleration of 26.3ft/sec^2.

Because stopping distance is very sensitive to initial speed, if your estimated speed of 60mph was really 61mph, average deceleration would be 27.2ft/sec^2. If speed was really 62mph, average deceleration would be 28.1ft/sec^2.

Going back to the table you posted earlier, which listed a 60-0 stopping distance of 134ft--for initial speed of 62mph, the same braking performance would result in a 143ft stop.


A superior rider uses superior judgment to avoid problems that would demand his superior skill.

Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 5/10/2010 8:54 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I do have to say that a few of the stops definitely felt much harder than the average. Makes me wonder if more practice would improve my results and shorten the distance a bit more. But also, if you take out the high and low values and average the rest, my average is only slightly better at 146.8 ft. Look at the pictures I posted into the earlier reply to show the tire marks and tire contact width during braking.

Now, consider that I have actually practiced and measured my results. I've been riding for 38+ years, and as a MSF instructor I seek out trying to do my best when riding. In the end, I find my results are average at best. But the bigger point is, I tested myself with measured results, instead of just claiming "I'm an experienced rider, I know what I'm doing." My bike has ABS, running on sport-touring tires, it has front suspension that limits front end "dive" during heavy braking. The steering geometry remains constant even under heavy braking, which is not typical for most cycles. For many bikes, under very heavy braking the front end dive is significant and can cause the bike to become more even more unstable.

Here is a program to determine the braking distance taking into account factors like the bike wheelbase and CG, and speed. http://www.msgroup.org/forums/mtt/images/StoppingDistance.xls

When I enter my values, based on a coefficient of friction of .80, it says my best braking distance would be 150'. So perhaps my average of 147' for my test is in line with the parameters of the test area.  


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org

Post Edited (Andy VH) : 5/13/2010 11:08:37 PM GMT

Back to Top
 

To The
Registered Member



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Feb 2008
Total Posts : 454
 
   Posted 7/18/2010 5:48 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I think .5 second is very generous. In our crash reconstruction problems we generally use a perception/reaction time of 1.5 seconds. Maybe less for young, athletic types and maybe more for older types. And just from watching motorists react to problems on the road, even THAT might be generous. Most relatively healthy people can probably react in a half-second, but there's also "perception time", the time it takes to decide what you're going to do, and THEN send the signal to your muscles to actually grab the brakes, activate them, heat up the rotors and slow or stop, or swerve, or do nothing.

Watch drivers or riders on the road when someone ahead of them does a panic stop for a line of ducks crossing the road....or some other situation. Lots of people take a lot more than .5 seconds to decide what they're going to do and then do it. If I can't see ahead of the vehicle I'm behind, ie. a truck or bus, to predict what THAT driver is going to do in case of trouble, I get very nervous and either get out in front of that vehicle or leave more room than 2 seconds, whether I'm riding or driving.
Back to Top
 

Andy VH
Where is the earth shattering kaboom!?



Email Address Not AvailablePersonal Homepage Not AvailablePrivate Messaging Not AvailableAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2005
Total Posts : 4952
 
   Posted 7/18/2010 3:42 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
A very good point, and I agree that a 1/2 second reaction time is probably at best! In reality I bet one second to 1-1/2 seconds would be realistic. Given that, again using 60 mph as a common reference speed, the distance relative to that speed is 88 feet per second. That equates to a distance of 88 feet to 132 feet. A common city lot is about 120' wide, use that as a reference. So watch other riders or car drivers and estimate how close they follow other traffic. I bet a very high percentage of road users follow MUCH closer than even 88 feet, much less 132 feet.

The MSF recommended minimum following distance is based on a 2-second timing. At 60,mph (88 feet per second) that equals 176 feet.


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org
 

Back to Top
 
You cannot post new topics in this forum. You cannot reply to topics in this forum. Printable Version
32 posts in this thread.
Viewing Page :
 1  2 
 
Forum Information
Currently it is Wednesday, March 29, 2017 11:35 PM (GMT -7)
There are a total of 500,924 posts in 39,661 threads.
In the last 3 days there were 0 new threads and 0 reply posts. View Active Threads
Who's Online
This forum has 21237 registered members. Please welcome our newest member, whhhhhaaaat.
1 Guest(s), 0 Registered Member(s) are currently online.  Details