N
Nate Nagel
Guest
Tim McNamara wrote:
> [email protected] (Brent P) writes:
>
>
>>In article <[email protected]>, Tim McNamara wrote:
>>
>>
>>>Indeed, my review of some of the traffic management literature
>>>(e.g.,
>>>http://ops.fhwa.dot.gov/Travel/traffic/freeway_management_handbook/chapter5.htm)
>>>suggests that traffic flow obeys the mathematics governing
>>>hydraulic flow, and that there is a maximum throughput in any
>>>hydraulic system before turbulence is created. Turbulence in turn
>>>creates drag and slows throughput dramatically. You can set the
>>>speed limit at the 85th percentile, but that will not "smooth out"
>>>traffic flow when there are just too many cars on the road at the
>>>same time- which is about 8 hours of every day in major urban
>>>areas.
>>
>>A smooth flow can sustain a higher throughput delaying the onset of
>>traffic jams and lessening how long they last.
>
>
> In an ideal world, sure. But you're dealing with a situation where by
> definition 85% of drivers are driving below the posted limit- which
> means the faster drivers are tailgating, trying to pass, and creating
> turbulence in the traffic flow. This rapidly becomes congestion.
> You're also dealing with drivers of radically different driving skills
> and driving preferences, so you get people driving 45 mph in the
> center lane on a road posted at 80 mph (in your ideal scenario of
> using the 85th percentile).
Whoa! Hod it right there! That person should get a ticket - no matter
what the speed limit is. That's a completely separate issue, and
another pet peeve of mine. Slow traffic stays to the right, faster
traffic passes to the left, that way nobody gets "held up" until the
highway is completely full. that's the way it's *supposed* to work,
anyway. The idea is to make it more like a laminar flow than a
completely turbulent one.
nate
--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel
> [email protected] (Brent P) writes:
>
>
>>In article <[email protected]>, Tim McNamara wrote:
>>
>>
>>>Indeed, my review of some of the traffic management literature
>>>(e.g.,
>>>http://ops.fhwa.dot.gov/Travel/traffic/freeway_management_handbook/chapter5.htm)
>>>suggests that traffic flow obeys the mathematics governing
>>>hydraulic flow, and that there is a maximum throughput in any
>>>hydraulic system before turbulence is created. Turbulence in turn
>>>creates drag and slows throughput dramatically. You can set the
>>>speed limit at the 85th percentile, but that will not "smooth out"
>>>traffic flow when there are just too many cars on the road at the
>>>same time- which is about 8 hours of every day in major urban
>>>areas.
>>
>>A smooth flow can sustain a higher throughput delaying the onset of
>>traffic jams and lessening how long they last.
>
>
> In an ideal world, sure. But you're dealing with a situation where by
> definition 85% of drivers are driving below the posted limit- which
> means the faster drivers are tailgating, trying to pass, and creating
> turbulence in the traffic flow. This rapidly becomes congestion.
> You're also dealing with drivers of radically different driving skills
> and driving preferences, so you get people driving 45 mph in the
> center lane on a road posted at 80 mph (in your ideal scenario of
> using the 85th percentile).
Whoa! Hod it right there! That person should get a ticket - no matter
what the speed limit is. That's a completely separate issue, and
another pet peeve of mine. Slow traffic stays to the right, faster
traffic passes to the left, that way nobody gets "held up" until the
highway is completely full. that's the way it's *supposed* to work,
anyway. The idea is to make it more like a laminar flow than a
completely turbulent one.
nate
--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel