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Old 03-24-2013, 11:44 AM   #196
Wraith Rider
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@CanadianX
Nice line-up, my slightly different figures (and denotations):

reaction time - average 300ms, under 200ms possible, your 500ms as an upper limit might be a bit optimistic
move-time (from throttle to brakes) - 300ms (motorcycle because of the shorter way) to 500ms (car as you described) - can greatly reduced, maybe halfed by hovering over the brake (in suspect situations)
braking pressure build up time - 200ms - may be shorter for smaller braking systems, are longer for pneumatic systems (lorry), can be nearly eliminated by braking assist systems (however, they won't have much of an effect if you hover over the brake as mentioned before)

Remember, brake lights flash up before braking pressure is completely build up (maybe not true with braking assist), so we have some safety buffer here. The partial braking on the other hand is not countable as a safety buffer, because the vehicle in front brakes as well partially while in the pressure build up time.

A good guess is to sumarize this to 1 second unbraked "reaction time" as it's regularily done in praxis, though you see it could well go down to maybe 600ms and me myself has video proof of doing the transition from event (while overtaking) to full braking in ~0.8s - but I'm always calculating conservatively to leave me some safety buffer.
So my table is:

30km/h - 8,34m - 3,86m - 12,2m
50 - 13,9 - 10,7 - 24,6
60 - 16,7 - 15,4 - 32,1
80 - 22,3 - 27,4 - 49,7
100 - 27,7 - 42,9 - 70,6
120 - 33,4 - 61,7 - 95,1

So your source calculates with a very good total reaction time of 0.66s and a quite bad deceleration of 6.5m/s - though it's reasonable to use such a low value because tests showed that riders without ABS (or with ABS but without instruction and training to use it) only reach these 6...7m/s in deceleration.

You're right when you say we need to add the total reaction time to our stopping distance. Exactly this is our minimum safety distance, what I was trying to explain to D_A and the likes but he doesn't want to see.
You're right as well when you talk about stopping distance car vs. bike. My ABS reaches 9.5m/s, I'm calculating with 9m/s, a car might or might not reach 11m/s.
Conclusion 1: If a car tailgates me it's not as bad as you thought, 'cause it most likely brakes at least as good as I and if not, I can release my brakes.
Conclusion 2: I could consider adding another 0.3s to compensate these 2m/s in the absolutely (and unlikely) worst case but odds are good we both brake at 9.5m/s and as I stated above, I have safety margins in my calculation.

Quote:
Originally Posted by CanadianX View Post
I'd say that if you are only leaving 1s between you and the vehicle in front then it is only a matter of time before you get in an accident or cause one behind you because you don't have smooth transitions between speeds and you are always jacking on the brakes to avoid accidents.
Well, everything is a matter of time. Everyone will crash someday if he rides indefinitely. However, it's extremely rare that someone undertakes an emergency braking in traffic without any apparent reason. It's even more unlikely that this coincides with the very moment the one following at minimum safety distance takes a look in the mirror. Especially when you consider that closing up normally happens after checking the mirror shortly before overtaking. (I think there's no measurable higher risk than with leaving your house at all.)

Quote:
Originally Posted by CanadianX View Post
Ever find that if you ride up the ass of someone and look in the mirror someone is riding your ass?
Well, since I tend to follow my own advices:
Quote:
Originally Posted by Wraith Rider View Post
If you're tailgated, you're too slow. If you're too slow, pull over. Problem solved.
Actually no. :-)
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Old 03-24-2013, 01:44 PM   #197
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Quote:
Originally Posted by randyo View Post
the biggest reason not to tailgate is so you can slow down more gradually so the guy behind you doesn't run over you

just cause you're superhuman doesn't mean the guy behind you is
That is why, when I ride, if someone is on my ass I slow ang make a big distance between me and the next car. Side benifit is that the guy behind me usually backs off or goes around.

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Old 03-24-2013, 11:46 PM   #198
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Laugh Slow vehicles stay right

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Originally Posted by rbmgf7 View Post
I would assume so but apparently DAKEZ isn't familiar with the "left lane is for passing only" law which is enforced in most states. I haven't seen a sign yet in VA but I still like to follow that guidance.

I'm sure DAKEZ wouldn't know much regardless since he's too busy flaming and building his post count instead of riding. So, an obligatory, "I'm a " for DAKEZ.



Yeah, I was firing from the hip. Whenever you enter Canada, some POEs have the speed conversion billboards and I distinctly remember 100KMH=60MPH. It was a quick and dirty conversion, lol.



What am I suppose to do about the teenager texting/talking on the phone while driving? How do I adapt to that? I'm certain that's a bigger concern than tailgating.



The one thing I do agree with you but metro is not rural. The moment you implement your 3-second rule in rush hour on an 8 lane super highway, that becomes an opening for a Latte-sipping Beemer driver. Riding a 2 lane country road, you can implement all the seconds you want
In Canada,at least in Alberta,home to the second busiest highway in Canada the road signs state "slow moving traffic stay right" there is no law prohibiting driving as long as you want in the left lane. during high traffic times on weekends the left lane generally travels at around 120 to 130km/hr. the right lane is filled with the rest. Motor homes,scaredy cats and transport trucks. Not perfect but works pretty well as out here on the prairies we like to cover big distance quick cuz everything is so spread out. When you can do that from the right lane we do just in case someone comes across the meridian into oncoming.
As far as this thread goes,aside from the childish infighting this has helped to open my eyes as generally I'm one of those"take no shit" types but when you look at the discussion it's pretty easy to see avoiding and defusing the situation is the best plan. Hard to do sometimes but still smartest. I find that the power and maneuverability of my Tiger makes it pretty easy to pin it and leave them behind I Think that qualifies as avoidance and you can yell "adios mutherfukker"or "Bye bye lardass" inside your helmet and make yourself grin
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Old 03-25-2013, 12:16 AM   #199
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Quote:
Originally Posted by D_A View Post
I've seen plenty of young guys who think their reflexes are top 1% and they can brake safely within one second. Not one of them could, even the ones who race. Most were very average at best.
Here the recommended distance is three seconds, though in the central city you will have people trying to leap into that gap and then sit a half second behind the vehicle in front. They will insist they are far enough behind to brake safely, and that they're not tailgating. They can't and they are.
I saw the claim above that a one second gap is enough time to brake and that "physics says" it's so. Sure, if you start to brake at the exact same time and rate as the vehicle in front then it's plenty of room, but that doesn't allow for human reflexes, wandering attention or that half second "WTF?!?" moment as the situation presents before you react, never mind misjudging the required braking force or road conditions you couldn't see because you were tailgating the vehicle in front.
Central West NSW? I used to live out there a long time ago.

Yeah, my old Man ran a trial course for the RTA for a while aimed at getting P platers to drive safely. The kids (and adults) would each get a traffic cone, stand at a line and put the cone where they thought they could stop their car from 50kph at.

They'd jump in their car, and while everyone else watched they'd get up to speed (50) and start braking from the white line. **All** of them sailed right over the top of their cones, even the ones with late model sports cars and ABS.

The day comprised of a series of tasks they had to perform, and after they failed the tasks they'd be taken into the classroom to understand why they failed.

One of the key things taught in the course was the 3 second rule. My old man admitted that you could probably safely reduce that to 2 seconds if you were a good driver and always paying attention, but the truth is most people don't pay attention and they will use up the entire first second spazzing out responding to whatever it is in front of them demands a decision.

Traffic rules are made for a statistical average of the lowest 12.5% of the bell curve.

Also, he explained why the 2 second gap was really important: tailgating is about rear-end crashes, right? Most people who argue for a 1 second gap make the assumption the car in front will brake successfully without coming to a sudden stop from an impact. The 2 second gap is to plan for a car that spends half it's time braking and comes to a sudden stop due to impact. Sure, if that vehicle's braking distance was allowed to fully play out, you'd pull up fine - but half that distance does not happen due to the impact. And thus you end up in the back of that car because 1/4 to 1/3 of your braking distance has been removed due to their sudden stop.

If you're 2 seconds behind them then that room allows for their sudden immediate stop due to impact, and this aspect of braking is not taken into account by the 'superhuman heroes' who think sitting half a second off someone's tail gives them time and room to pull up.
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Old 03-25-2013, 12:35 AM   #200
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Originally Posted by gastone View Post
I'm with the above two posters. I braked checked a tailgater only to have him pull up beside me and swerve into me and make contact with my bars...twice. Now I'm inclined to let them go by.
I've hit the tarmac a few times now, and I don't really like it so much anymore. I agree with you, I'm not riding for them, I don't care what they think, and a few bounces off the hard stuff has knocked a lot of Ego out of me.

These days I ride to stay alive and enjoy myself. I wave tailgaters by or get out of their way. Defending my little ego against someone I neither know or care about isn't worth it. Especially here in Sydney where more people are road-raging others for the slightest slights, and many are killed or maimed in the process. A woman with her kids in the car recently rammed a guy and crushed his pelvis. I bet that guy is thinking "yeah, escalating that road rage incident really paid off!"

Sacrificing a little bit of ego and letting a bit of offense slide is a small price to pay for staying upright and not doing hospital time (again...) ;-)
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Old 03-25-2013, 12:55 AM   #201
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Quote:
Originally Posted by Wraith Rider View Post
Remember, brake lights flash up before braking pressure is completely build up
Err the electrical circuit may close before the brake is fully applied... but

For an incandescent globe there is a thermal reaction time to build up the temperature of the filament.

For a LED there is much less time from current flow to light output - thus you might get 0.2 seconds advance warning using LEDs .. if the following rider/driver is looking and awake...

======================
Where would you rather have a fool? In front where you can keep and eye on them, or behind where they are not so well monitored?

===============
There was a case in Western Australia. A semi trailer driver (you call them tractor trailers) was driving down one of our typical straight stretches of road. Decided to have a drink from a pop can. Drove straight in to the rear of a van. And killed the bicycle rider in front of that. The van had flashing lights and a large sign saying "Cyclist in front". The semi trailer drive said he did not see it.. probably too thirsty? Don't think he even saw jail time...
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Old 03-25-2013, 06:28 AM   #202
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Quote:
Originally Posted by Platinumgrit View Post
sitting half a second off someone's tail gives them time and room to pull up.

second is generous, so many times in metro traffic cars are barely a car length apart @ 60mph or about 0.15 seconds and then they wonder why they got caught in a 150 car pileup
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Old 03-25-2013, 08:29 AM   #203
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But if you have ABS brakes you don't have to worry because they will save you EVERY time! No... Really. You can't even get hit by an asteroid if you have ABS and deer whistles are a standard feature built right into the ABS system on ALL bikes so equipped.
Not true. I got hit by a June bug once, right in the throat. ABS didn't save me. That felt like getting hit by an asteroid.
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Old 03-25-2013, 08:30 AM   #204
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Old 03-25-2013, 08:55 AM   #205
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This is getting funny,

The justifications some use for reducing their margins and options, humility is the most important safety formula.
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Old 03-25-2013, 09:19 AM   #206
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Have to ride like everyone else is an idiot or crazy or both.

Just yesterday in my car I'm in a 50 MPH zone...car in front of me is only doing 40. Can't pass as the road is curvy. Up behind me comes Mr idiot in a pickup....he's riding my ass.....what the hell riding my ass isn't going to make granny in front go any faster.....road straightens out with a passing zone....can't pass, cars are coming the other way. Once they clear there is just enough left of the passing zone to make a safe pass....I go around granny at about 60MPH....of course Mr Pickup follows....I get back in line just as the passing zone ends and here comes another pickup....Mr idiot decided he doesn't want to be behind me either and continues in the on coming lane to pass me....I could have been an ass and accelrated but whats the point....he makes it in front of me just in time to miss the on coming truck. Now here is the funny your a douche part...not 500 feet up the road he turns left to a side road....WTF why did you pass me for if you were gonna turn anyway Gave him the salute as I went by....
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Old 03-25-2013, 10:07 AM   #207
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Quote:
Originally Posted by Platinumgrit View Post
The 2 second gap is to plan for a car that spends half it's time braking and comes to a sudden stop due to impact.
That's completely random. Why half and not one or three quarter? Why assume it will brake at all? And if an impact is oncoming, why should I wait with my own braking until the brake lights in front of me flash up?

Quote:
Originally Posted by Warin View Post
Where would you rather have a fool? In front where you can keep and eye on them, or behind where they are not so well monitored?
Doesn't really matter that much. I have mirrors. In general I tend to get away from both quite quickly.
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Old 03-25-2013, 10:25 AM   #208
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Old 03-25-2013, 11:36 AM   #209
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Quote:
Originally Posted by Offcamber View Post
Have to ride like everyone else is an idiot or crazy or both.

Just yesterday in my car I'm in a 50 MPH zone...car in front of me is only doing 40. Can't pass as the road is curvy. Up behind me comes Mr idiot in a pickup....he's riding my ass.....what the hell riding my ass isn't going to make granny in front go any faster.....road straightens out with a passing zone....can't pass, cars are coming the other way. Once they clear there is just enough left of the passing zone to make a safe pass....I go around granny at about 60MPH....of course Mr Pickup follows....I get back in line just as the passing zone ends and here comes another pickup....Mr idiot decided he doesn't want to be behind me either and continues in the on coming lane to pass me....I could have been an ass and accelrated but whats the point....he makes it in front of me just in time to miss the on coming truck. Now here is the funny your a douche part...not 500 feet up the road he turns left to a side road....WTF why did you pass me for if you were gonna turn anyway Gave him the salute as I went by....
I was with you until I read this. Why in hell would you even consider accelerating??!! You really want to maybe kill the pickup driver, his passengers, the oncoming truck because you don't like the way the guy drives? Wow. I thinks you need to learn to chill. Or don't drive. One or the other.

Reading Wraith's comments reminds me of an exhibit at the Science Centre here about 30 years ago. It was set up with a steering wheel, brake and gas pedals and two lights in front of you - one red, one green. When the green light was on, you applied gas. When the red lit up you hit the brakes as fast as you could. The resulting time was displayed. Almost NO ONE ever got below one second. Lots of young hot shots thought they'd have no problem. That exhibit was only dealing with reaction time - time to perceive and time to move foot. Even if you make the one second reaction you are still stuck with being one second behind in brake application. Oh well, another internet "discussion" where no opinions ever get alterred, regardless of how misguided.
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Old 03-25-2013, 11:47 AM   #210
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.7s is a very fast reaction time, and it doesn't include the loading of the front suspension that is required for maximum braking pressure. You're also not going to be prepared to do a max effort quick stop so dd another half a second to gauge the vehicles actual deceleration rate. By then it is too late, enjoy the bumper.
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