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Misreperesention of relative stopping distances of cars and trucks in Ny Driver's Manual



 
 
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  #31  
Old January 2nd 05, 07:32 PM
Timothy J. Lee
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In article >,
Arif Khokar > wrote:
>Timothy J. Lee wrote:
>> Arif Khokar > wrote:

>
>>>You ought to read how they determine reaction times in the AASHTO "Green
>>>Book." They say the average reaction time for a driver is around *2*
>>>seconds, which is total bull**** IMO.

>
>> Given how a large percentage of the driving public is either distracted
>> (by cell phones or other things) or just not paying that much attention
>> to driving, it would not be surprising that many of them have a reaction
>> time of 2 or more seconds. Especially when they have to see that the brake
>> lamps on the car ahead mean "stopping quickly" rather than the more common
>> "slowing down gradually".

>
>Stopping is rarely the only option to avoid an obstacle.


Most minimally skilled drivers of the type described above are unlikely
to consider other options like changing lanes, or be aware whether the
lane(s) next to them are clear at the time they see an obstacle. Plus,
some of them may not be skilled enough to do an emergency lane change
without spinning out (I have seen that happen -- the spinning car then
hit another car, causing that other car to spin, resulting in a third car
hitting the spinning second car). And if the unskilled driver is in a
top heavy SUV with underinflated poor quality tires, the result can be
worse.

>>>Even the Bosch Automotive handbook states
>>>that the average reaction time is around 0.8 to 1.2 seconds, IIRC.

>
>> Isn't Bosch based in a country where driver's licensing standards are
>> stricter than in the US?

>
>Well, I'm pretty sure that stricter licensing standards would not
>decrease one's reaction time by 50%.


Given the other threads about how some drivers take up to 5 seconds to
notice that their traffic light just changed from red to green, is it
hard to believe that some drivers on the roads have reaction times that
are much longer than what a skilled attentive driver should have?

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  #32  
Old January 2nd 05, 07:56 PM
tscottme
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Yes it's a devilish plot to corrupt the world. They've discovered that a
sly insertion of an erroneous graph in a state's driver manual is certain to
rapidly spread their propoganda to everyone on earth.

Just go speed and stop making excuses or looking for conspiracies.

--

Scott

Like the archers of Agincourt, John O'Neill and the 254 Swiftboat Veterans
took down their own haughty Frenchman. - Ann Coulter


  #33  
Old January 2nd 05, 07:56 PM
tscottme
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Yes it's a devilish plot to corrupt the world. They've discovered that a
sly insertion of an erroneous graph in a state's driver manual is certain to
rapidly spread their propoganda to everyone on earth.

Just go speed and stop making excuses or looking for conspiracies.

--

Scott

Like the archers of Agincourt, John O'Neill and the 254 Swiftboat Veterans
took down their own haughty Frenchman. - Ann Coulter


  #34  
Old January 2nd 05, 08:06 PM
SideBand
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Jack Brown wrote:
> Apparently the New York Department of Motor Vehicles does not know
> how to graph. Look at this graph from the drivers manual below. The
> Stopping distance for a car is 193 ft but it is plotted as about 110 ft.
> Is this a stupid mistake or an attempt to scare drivers into being
> afraid of trucks?
>
> http://www.nydmv.state.ny.us/dmanual/stopdist.gif
>

Not really the first time New York State has misrepresented something,
now is it?
  #35  
Old January 2nd 05, 08:06 PM
SideBand
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Jack Brown wrote:
> Apparently the New York Department of Motor Vehicles does not know
> how to graph. Look at this graph from the drivers manual below. The
> Stopping distance for a car is 193 ft but it is plotted as about 110 ft.
> Is this a stupid mistake or an attempt to scare drivers into being
> afraid of trucks?
>
> http://www.nydmv.state.ny.us/dmanual/stopdist.gif
>

Not really the first time New York State has misrepresented something,
now is it?
  #36  
Old January 3rd 05, 04:57 AM
Brent P
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In article >, Nate Nagel wrote:

> You mean most people don't rip half their suspension apart every time
> they hear a funny noise? (boggle) Ask me how I've spent my last couple
> weekends. Go ahead, ask me (sigh.)


I don't tear it apart, but I at least put the car up and try to figure
out what it is and repair it if need be. At least this way I know there
is no impending major failure.

I don't like something the mustang's front end is doing when I back out
of parking places in the cold. But I think it's the tires' directional
tread causing it. I can find nothing wrong and nothing seems loose or
worn out.


  #37  
Old January 3rd 05, 04:57 AM
Brent P
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In article >, Nate Nagel wrote:

> You mean most people don't rip half their suspension apart every time
> they hear a funny noise? (boggle) Ask me how I've spent my last couple
> weekends. Go ahead, ask me (sigh.)


I don't tear it apart, but I at least put the car up and try to figure
out what it is and repair it if need be. At least this way I know there
is no impending major failure.

I don't like something the mustang's front end is doing when I back out
of parking places in the cold. But I think it's the tires' directional
tread causing it. I can find nothing wrong and nothing seems loose or
worn out.


  #38  
Old January 5th 05, 07:32 PM
Robert Briggs
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AZGuy wrote:

> I haven't check it in a while but my memory was that it was
> PERCEPTION-REACTION time, not just reaction time. In any event,
> it's going to be conservative.


That makes sense, since the initial time lag has to account for
switching your foot from the throttle to the brake pedal, which
takes a lot longer than simply pressing a button in a test of your
reaction time.

The UK's Highway Code formula uses a "thinking distance" of one
foot per mile per hour, which corresponds to about 0.67 s.

> If you go thru their various design requirements you find that
> they assume a usable coefficient of friction for design purposes
> of around 0.25, which is quite low compared to what's typically
> the case, however it is about right if you assume the worst case.


For it braking distances, the Highway Code formula takes the speed
in mph, squares it, and divides by 20, which corresponds to a
deceleration of about 0.67 g.

OTOH, the "MoT" roadworthiness test requires only 0.5 g of braking
ability. This means that a car which is just legal can be quite
incapable of stopping in the Highway Code formula's distance even
if the driver is very much alert. (All this assumes a good road
surface, of course.)

The whole Highway Code formula, applied to a speed of 55 mph, gives
an overall stopping distance of 206' 3", so the quoted 193' looks
reasonable.

I have used the Highway Code formula of my youth.

These days the distances are given in metres, but they seem to be
simply the old imperial distances converted and rounded to whole
metres. IOW, they haven't taken the opportunity to bring the
Highway Code's assumed braking performance into line with the MoT's
requirement.

IIRC, a new easy-to-remember-and-use formula would assume something
very close to the MoT's 0.5 g braking ability.
  #39  
Old January 5th 05, 07:32 PM
Robert Briggs
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AZGuy wrote:

> I haven't check it in a while but my memory was that it was
> PERCEPTION-REACTION time, not just reaction time. In any event,
> it's going to be conservative.


That makes sense, since the initial time lag has to account for
switching your foot from the throttle to the brake pedal, which
takes a lot longer than simply pressing a button in a test of your
reaction time.

The UK's Highway Code formula uses a "thinking distance" of one
foot per mile per hour, which corresponds to about 0.67 s.

> If you go thru their various design requirements you find that
> they assume a usable coefficient of friction for design purposes
> of around 0.25, which is quite low compared to what's typically
> the case, however it is about right if you assume the worst case.


For it braking distances, the Highway Code formula takes the speed
in mph, squares it, and divides by 20, which corresponds to a
deceleration of about 0.67 g.

OTOH, the "MoT" roadworthiness test requires only 0.5 g of braking
ability. This means that a car which is just legal can be quite
incapable of stopping in the Highway Code formula's distance even
if the driver is very much alert. (All this assumes a good road
surface, of course.)

The whole Highway Code formula, applied to a speed of 55 mph, gives
an overall stopping distance of 206' 3", so the quoted 193' looks
reasonable.

I have used the Highway Code formula of my youth.

These days the distances are given in metres, but they seem to be
simply the old imperial distances converted and rounded to whole
metres. IOW, they haven't taken the opportunity to bring the
Highway Code's assumed braking performance into line with the MoT's
requirement.

IIRC, a new easy-to-remember-and-use formula would assume something
very close to the MoT's 0.5 g braking ability.
  #40  
Old January 6th 05, 12:00 AM
Olaf Gustafson
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On Sun, 02 Jan 2005 02:17:24 GMT, Arif Khokar >
wrote:

>Nate Nagel wrote:
>
>> I just took a look at the graph from the original post and yes it does
>> look like it was thrown together by a third grader, but also notice that
>> the distances include "reaction distance recommended by the National
>> Safety Council" which probably assumes a .7 second or greater RT (i.e.
>> brain dead) - another common inaccuracy with such graphs.

>
>You ought to read how they determine reaction times in the AASHTO "Green
>Book." They say the average reaction time for a driver is around *2*
>seconds, which is total bull**** IMO.


I don't know about that. I was behind someone the other day when the
light turned yellow in front of them. When they didn't put on their
brakes for about 2 seconds, I assumed they weren't going to stop for
it - and they shouldn't have stopped for it.

But they did stop. I nearly hit them, which would have sucked because
it would have been my fault.

> As for 0.7 second figure, I don't
>think that it's unreasonable. Even the Bosch Automotive handbook states
>that the average reaction time is around 0.8 to 1.2 seconds, IIRC.


 




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