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Prevailing Speed vs Posted Speed Limit



 
 
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  #1  
Old August 28th 06, 05:58 PM posted to rec.autos.driving
Bob Simon
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Posts: 4
Default Prevailing Speed vs Posted Speed Limit

I am trying to convince my wife that if safety is your highest
concern, then it is better to drive the prevailing speed than the
speed limit. If this is in fact true, can anyone point me to an
authoritative source?
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  #2  
Old August 28th 06, 06:01 PM posted to rec.autos.driving
Matthew Russotto
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Posts: 1,429
Default Prevailing Speed vs Posted Speed Limit

In article >,
Bob Simon > wrote:
>I am trying to convince my wife that if safety is your highest
>concern, then it is better to drive the prevailing speed than the
>speed limit. If this is in fact true, can anyone point me to an
>authoritative source?


Take your wife out on a local highway during a period where there is
moderate traffic and the prevailing speed is significantly greater
than the limit. Sit in the right lane doing the speed limit, and make
sure there's nothing to distract her. If that doesn't convince her,
give up.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.
  #3  
Old August 28th 06, 06:09 PM posted to rec.autos.driving
[email protected]
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Posts: 5
Default Prevailing Speed vs Posted Speed Limit

In article >,
Bob Simon > wrote:

> I am trying to convince my wife that if safety is your highest
> concern, then it is better to drive the prevailing speed than the
> speed limit. If this is in fact true, can anyone point me to an
> authoritative source?



Researchers working for the government (D. Solomon, "Accidents on Main
Rural Highways Related to Speed, Driver, and Vehicle," Federal Highway
Administration, Washington, DC, July 1964, Reprinted 1974 & J. A.
Cirillo, "Interstate System Accident Research Study II, Interim Report
II," Public Roads, Vol. 35, No. 3, August 1968) found that drivers
traveling between 5 and 15 mph above the AVERAGE speeds (not speed
LIMITS) have the least amount of 'crash involvement.'

http://motorists.org/ma/chart.html
  #4  
Old August 28th 06, 06:25 PM posted to rec.autos.driving
Floyd Rogers[_1_]
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Posts: 689
Default Prevailing Speed vs Posted Speed Limit

"Bob Simon" > wrote
>I am trying to convince my wife that if safety is your highest
> concern, then it is better to drive the prevailing speed than the
> speed limit. If this is in fact true, can anyone point me to an
> authoritative source?


The most authoritative source is the MUTCD (Manual for Uniform
Traffic Control Devices, which is the US DOT guide for signage,
speed limits, etc. The main concept regarding the setting of speed
limits is the 85th percentile rule, where the speed limit is set at
the speed at which 85% of the traffic is going below (there's
a big section on how to measure this...)

There is much debate on how speed limits are actually set
versus the 85th percent rule: many limits are set substantially
below the 85th. Some places, like school zones, clearly need
to be set lower, but many more don't.

For a great chart, see: http://www.tfhrc.gov/safety/speed/speed.htm
and look at figure 1, which charts the crash involvement vs. deviation
from 85th. You're *MUCH* better off to be a little faster than average
and 85th.

FloydR


  #5  
Old August 28th 06, 06:35 PM posted to rec.autos.driving
Brent P[_1_]
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Posts: 8,639
Default Prevailing Speed vs Posted Speed Limit

In article >, Floyd Rogers wrote:

> For a great chart, see: http://www.tfhrc.gov/safety/speed/speed.htm
> and look at figure 1, which charts the crash involvement vs. deviation
> from 85th. You're *MUCH* better off to be a little faster than average
> and 85th.


And crash involvement rate is the best measure IMO.
  #6  
Old August 28th 06, 07:19 PM posted to rec.autos.driving
C. E. White[_1_]
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Posts: 933
Default Prevailing Speed vs Posted Speed Limit


> wrote in message
...
> In article >,
> Bob Simon > wrote:
>
>> I am trying to convince my wife that if safety is your highest
>> concern, then it is better to drive the prevailing speed than the
>> speed limit. If this is in fact true, can anyone point me to an
>> authoritative source?

>
>
> Researchers working for the government (D. Solomon, "Accidents on Main
> Rural Highways Related to Speed, Driver, and Vehicle," Federal Highway
> Administration, Washington, DC, July 1964, Reprinted 1974 & J. A.
> Cirillo, "Interstate System Accident Research Study II, Interim Report
> II," Public Roads, Vol. 35, No. 3, August 1968) found that drivers
> traveling between 5 and 15 mph above the AVERAGE speeds (not speed
> LIMITS) have the least amount of 'crash involvement.'


Wow, do you think a 40 year old studies are really relevant to today? And
they don't address what sort of accidents drivers going 10 or 20 mph over
the limit leave in their wake. You don't have to be involved in an accident
to be part of the cause of an accident. And using "Vehicle Involvement" as
the measurement ignores the possibility that accidents at higher speeds most
likely result in higher injury and property losses. Also, this is another
case where you can't separate cause from effect. It is my perception that
slower drivers tend to be older drivers, newer inexperienced drivers, or
fearful, nervous drivers. These drivers have more accidents because they are
bad drivers, not because they are slower drivers. I do admit drivers that
drive significantly lower than the prevailing speed can be responsible for
accidents they are not actually part of (just like faster drivers). Your 40
year old studies seem to be less than an authoritative source for today's
conditions.

Ed


  #7  
Old August 28th 06, 07:30 PM posted to rec.autos.driving
C. E. White[_1_]
external usenet poster
 
Posts: 933
Default Prevailing Speed vs Posted Speed Limit


"Floyd Rogers" > wrote in message
...
> "Bob Simon" > wrote
>>I am trying to convince my wife that if safety is your highest
>> concern, then it is better to drive the prevailing speed than the
>> speed limit. If this is in fact true, can anyone point me to an
>> authoritative source?

>
> The most authoritative source is the MUTCD (Manual for Uniform
> Traffic Control Devices, which is the US DOT guide for signage,
> speed limits, etc. The main concept regarding the setting of speed
> limits is the 85th percentile rule, where the speed limit is set at
> the speed at which 85% of the traffic is going below (there's
> a big section on how to measure this...)


But what is the scientific basis for this rule? I have read the MUTCD
verbage on this, and it pretty much nets out as "use the 85th percentage
rule becasue we said so." It is just an arbitrary number somebody pulled out
of their butt. And the procedures for determining the 85th percentile are
largely unworkable. All in all, it is just an arbitrary number engineers can
quote to provide a faux-scientific reason for setting a speed limit.

> There is much debate on how speed limits are actually set
> versus the 85th percent rule: many limits are set substantially
> below the 85th. Some places, like school zones, clearly need
> to be set lower, but many more don't.
>
> For a great chart, see: http://www.tfhrc.gov/safety/speed/speed.htm
> and look at figure 1, which charts the crash involvement vs. deviation
> from 85th. You're *MUCH* better off to be a little faster than average
> and 85th.


This reference also makes a strong case for lowering speed limits (see Table
3) . I am against lowering speed limits.


  #8  
Old August 28th 06, 07:31 PM posted to rec.autos.driving
N8N
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Posts: 3,477
Default Prevailing Speed vs Posted Speed Limit


C. E. White wrote:
> > wrote in message
> ...
> > In article >,
> > Bob Simon > wrote:
> >
> >> I am trying to convince my wife that if safety is your highest
> >> concern, then it is better to drive the prevailing speed than the
> >> speed limit. If this is in fact true, can anyone point me to an
> >> authoritative source?

> >
> >
> > Researchers working for the government (D. Solomon, "Accidents on Main
> > Rural Highways Related to Speed, Driver, and Vehicle," Federal Highway
> > Administration, Washington, DC, July 1964, Reprinted 1974 & J. A.
> > Cirillo, "Interstate System Accident Research Study II, Interim Report
> > II," Public Roads, Vol. 35, No. 3, August 1968) found that drivers
> > traveling between 5 and 15 mph above the AVERAGE speeds (not speed
> > LIMITS) have the least amount of 'crash involvement.'

>
> Wow, do you think a 40 year old studies are really relevant to today? And
> they don't address what sort of accidents drivers going 10 or 20 mph over
> the limit leave in their wake. You don't have to be involved in an accident
> to be part of the cause of an accident. And using "Vehicle Involvement" as
> the measurement ignores the possibility that accidents at higher speeds most
> likely result in higher injury and property losses. Also, this is another
> case where you can't separate cause from effect. It is my perception that
> slower drivers tend to be older drivers, newer inexperienced drivers, or
> fearful, nervous drivers. These drivers have more accidents because they are
> bad drivers, not because they are slower drivers. I do admit drivers that
> drive significantly lower than the prevailing speed can be responsible for
> accidents they are not actually part of (just like faster drivers). Your 40
> year old studies seem to be less than an authoritative source for today's
> conditions.
>
> Ed


If you have a more authoritative study to discuss, please post it.

nate

  #9  
Old August 28th 06, 07:32 PM posted to rec.autos.driving,misc.transport.road,alt.law-enforcement.traffic,talk.politics.misc,alt.true-crime
Speeders & Drunk Drivers are MURDERERS[_1_]
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Posts: 3,043
Default Prevailing Speed vs Posted Speed Limit

On Mon, 28 Aug 2006 11:58:36 -0500, Bob Simon >
wrote:

>I am trying to convince my wife that if safety is your highest
>concern, then it is better to drive the prevailing speed than the
>speed limit. If this is in fact true, can anyone point me to an
>authoritative source?


It's called common sense. Slow is always safer. I've driven at or
below the speed limit all my life. Stop being a gutless sheep who
goes along with the crowd on everything.
  #10  
Old August 28th 06, 07:33 PM posted to rec.autos.driving
C. E. White[_1_]
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Posts: 933
Default Prevailing Speed vs Posted Speed Limit


"Brent P" > wrote in message
. ..
> In article >, Floyd Rogers wrote:
>
>> For a great chart, see: http://www.tfhrc.gov/safety/speed/speed.htm
>> and look at figure 1, which charts the crash involvement vs. deviation
>> from 85th. You're *MUCH* better off to be a little faster than average
>> and 85th.

>
> And crash involvement rate is the best measure IMO.


Why not death rate, or injury rate, or property damage? Crash involvement
includes trivial accidents. Surely you don't consider a scrapped fender to
be as bad as 65 mph crash into a bridge abutment? And how do you include
accidents that are triggered by other drivers that don't actually become
involved?

Ed


 




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