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Traffic flow

Started by webny99, May 31, 2017, 12:22:47 AM

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webny99

Which interstates can handle and process high volumes of traffic despite having few lanes based on AADT?

And which ones seem to face congestion despite what should be plenty of lanes to handle the volume?



fillup420

I-40/85 between Greensboro and Durham is 8-10 lanes across and from my experience, it is very good at handling high traffic volumes. It may have something to do with the fact the everyone ignores the 65 mph limit.

On the other end of the spectrum, I-77 north of Charlotte is awful; 4 lanes across, and rapid development in the past 20 years has clogged up the highway with local traffic. Many folks get on I-77 to go like 2 or 3 miles. This in addition to long-haul traffic creates a nightmare. There is currently a project to add toll lanes from mile 11 to mile 36, but the contracted company is shady, and the toll lanes won't actually help traffic.

epzik8

I feel like the I-95 JFK Highway between Baltimore and Newark, Delaware is an example of both. The traffic there flows well when nothing is hindering it, but when there's a problem, it's nightmarish.
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sparker

There's a "Catch-22" attached to the issue of traffic volume handling, particularly when it comes to Interstates.  The system was intended to be optimized for the anticipated traffic flow in a very straightforward manner:  segments close to or within urban areas were planned with additional lanes to handle the increased traffic, while most intercity routes (where the expected traffic centers were at least 50-75 miles apart) were mostly planned as 4-lane (2+2) facilities, as this was historically deemed adequate to deal with intercity traffic flow.  While this overall concept has proven prescient in some instances (such as the Midwest, where for the most part traffic does disperse between metro regions), it has been problematic elsewhere, particularly when overall average AADT is considerably less than peak data indicates.  A CA example is I-5 between the CA 99 junction at Wheeler Ridge and the I-580 "split" north of Patterson; it's 4-lanes, which is adequate about 80-85% of the time -- but when holiday interregional traffic levels increase dramatically, the 250+ mile segment bogs down and becomes a barely moving conveyor belt!  There have been periodic calls to expand it to 6 overall lanes, particularly south of CA 152 (where some San Jose traffic departs), but no funding for such an activity has ever been forthcoming.  One of the rationales occasionally cited for designating CA 99 as an Interstate is to potentially draw traffic away from the parallel I-5 facility and, again potentially, obviating the need to expand I-5 (the published plan for 99 is for, ultimately, a minimum of 6 lanes from I-5 north to Sacramento). 

Other regions have experienced similar circumstances; I-75 from Detroit north to Saginaw was expanded out to 6 lanes in the late '80's to accommodate the high traffic volumes, and the I-35 corridor in Texas, recently completed, was similarly built out from San Antonio to DFW (with portions in Austin and Waco that are still, despite the build-out, viewed as inadequate for the flow).  Others have been slow to expand; just now the AR segment of I-40 between Little Rock and Memphis is being planned for expansion due to the exceptionally heavy volume of trucks (this is often used as a rationale for the center segment of I-69); the problem has persisted for at least a quarter-century.  It seems today that if sizeable metro areas (250-300K or more) are less than 150 miles apart, an Interstate connecting them will, if remaining at 4 total lanes, experience regularized congestion on a continuing basis.   

Tonytone

Quote from: webny99 on May 31, 2017, 11:14:03 PM
Quote from: sparker on May 31, 2017, 11:01:09 PM
It seems today that if sizeable metro areas (250-300K or more) are less than 150 miles apart, an Interstate connecting them will, if remaining at 4 total lanes, experience regularized congestion on a continuing basis.

This could lead to an interesting debate  :biggrin: Personally, I agree 100%, but I'm sure some folks have vastly different views.

Like Sparker and ep said Delaware is a great example, De-1 Is 2-2. Plans are to expand it to 3 both ways, currently only the north bound side from the Route 40 exit is 3 Lanes, Before traffic used to be backed up all the way to Tybouts Corner, It's amazing how an extra lane can ease traffic. (Goes to show the days of 2-2 Highways are over).  but it drops as a off ramp for 273, and that causes a bottle neck to the New De-1-I-95 Interchange  ramps designed to Speed up traffic. I-95 Thru Delaware is 4-4  I think from the Chrsitiana Flyover ramps to I-495 is 5-5 Traffic thru this area is also heavy but it moves. The Blueball Interchange slows traffic down because drivers have to merge.
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sparker

Quote from: Tonytone on June 01, 2017, 12:51:54 AM
Quote from: webny99 on May 31, 2017, 11:14:03 PM
Quote from: sparker on May 31, 2017, 11:01:09 PM
It seems today that if sizeable metro areas (250-300K or more) are less than 150 miles apart, an Interstate connecting them will, if remaining at 4 total lanes, experience regularized congestion on a continuing basis.

This could lead to an interesting debate  :biggrin: Personally, I agree 100%, but I'm sure some folks have vastly different views.

Like Sparker and ep said Delaware is a great example, De-1 Is 2-2. Plans are to expand it to 3 both ways, currently only the north bound side from the Route 40 exit is 3 Lanes, Before traffic used to be backed up all the way to Tybouts Corner, It's amazing how an extra lane can ease traffic. (Goes to show the days of 2-2 Highways are over).  but it drops as a off ramp for 273, and that causes a bottle neck to the New De-1-I-95 Interchange  ramps designed to Speed up traffic. I-95 Thru Delaware is 4-4  I think from the Chrsitiana Flyover ramps to I-495 is 5-5 Traffic thru this area is also heavy but it moves. The Blueball Interchange slows traffic down because drivers have to merge.
My viewpoint stems from years of sifting through AADT stats, talking to DOT employees in various states (including my own), and one hell of a lot of personal anecdotal experience.  Opinions and viewpoints to the contrary are always welcome; I have no pretense as to being any more than one of many here and elsewhere who've engaged in some form of research on the issue.  As far as DE 1 is concerned, I have no doubt that at the north end of the route 6 overall lanes would be appropriate; south of the C-D canal bridge would be another story -- I'd have to look at the figures to come to any preliminary conclusion as to widening there. 

Tonytone

Quote from: sparker on June 01, 2017, 01:37:33 AM
Quote from: Tonytone on June 01, 2017, 12:51:54 AM
Quote from: webny99 on May 31, 2017, 11:14:03 PM
Quote from: sparker on May 31, 2017, 11:01:09 PM
It seems today that if sizeable metro areas (250-300K or more) are less than 150 miles apart, an Interstate connecting them will, if remaining at 4 total lanes, experience regularized congestion on a continuing basis.

This could lead to an interesting debate  :biggrin: Personally, I agree 100%, but I'm sure some folks have vastly different views.

Like Sparker and ep said Delaware is a great example, De-1 Is 2-2. Plans are to expand it to 3 both ways, currently only the north bound side from the Route 40 exit is 3 Lanes, Before traffic used to be backed up all the way to Tybouts Corner, It's amazing how an extra lane can ease traffic. (Goes to show the days of 2-2 Highways are over).  but it drops as a off ramp for 273, and that causes a bottle neck to the New De-1-I-95 Interchange  ramps designed to Speed up traffic. I-95 Thru Delaware is 4-4  I think from the Chrsitiana Flyover ramps to I-495 is 5-5 Traffic thru this area is also heavy but it moves. The Blueball Interchange slows traffic down because drivers have to merge.
My viewpoint stems from years of sifting through AADT stats, talking to DOT employees in various states (including my own), and one hell of a lot of personal anecdotal experience.  Opinions and viewpoints to the contrary are always welcome; I have no pretense as to being any more than one of many here and elsewhere who've engaged in some form of research on the issue.  As far as DE 1 is concerned, I have no doubt that at the north end of the route 6 overall lanes would be appropriate; south of the C-D canal bridge would be another story -- I'd have to look at the figures to come to any preliminary conclusion as to widening there.

South of the Canel could use it, The 3 lanes from Tybouts Corner to The toll after the bridge does the job, construction or an accident is the only thing that really slows traffic down.  Traffic gets heavy around the Smyrna exits and down to Dover This area could use 3 lanes, Also a lack of exits is one of the reasons to blame for congestion. Deldot likes to do stuff in a A-B-C manner.
Promoting Cities since 1998!

cpzilliacus

Quote from: sparker on June 01, 2017, 01:37:33 AM
My viewpoint stems from years of sifting through AADT stats, talking to DOT employees in various states (including my own), and one hell of a lot of personal anecdotal experience.  Opinions and viewpoints to the contrary are always welcome; I have no pretense as to being any more than one of many here and elsewhere who've engaged in some form of research on the issue.  As far as DE 1 is concerned, I have no doubt that at the north end of the route 6 overall lanes would be appropriate; south of the C-D canal bridge would be another story -- I'd have to look at the figures to come to any preliminary conclusion as to widening there.

The state-of-the-art way to measure traffic flow on freeways and arterial highways is with vehicle probe data (relatively easy to do).  Massive datasets that cover every hour of every day, with more coming.
Opinions expressed here on AAROADS are strictly personal and mine alone, and do not reflect policies or positions of MWCOG, NCRTPB or their member federal, state, county and municipal governments or any other agency.

kalvado

Quote from: cpzilliacus on June 01, 2017, 08:01:17 AM
Quote from: sparker on June 01, 2017, 01:37:33 AM
My viewpoint stems from years of sifting through AADT stats, talking to DOT employees in various states (including my own), and one hell of a lot of personal anecdotal experience.  Opinions and viewpoints to the contrary are always welcome; I have no pretense as to being any more than one of many here and elsewhere who've engaged in some form of research on the issue.  As far as DE 1 is concerned, I have no doubt that at the north end of the route 6 overall lanes would be appropriate; south of the C-D canal bridge would be another story -- I'd have to look at the figures to come to any preliminary conclusion as to widening there.

The state-of-the-art way to measure traffic flow on freeways and arterial highways is with vehicle probe data (relatively easy to do).  Massive datasets that cover every hour of every day, with more coming.

And with any huge dataset comes the problem of data reduction to digestible form. And then - guess what? - AADT would still be one of the metrics, if not THE metric. Understanding what is going on may be more involved, as evidenced by this thread. It can be about peak hour traffic, about weekend/holiday traffic, accident/construction related traffic and what not. Monitoring traffic 365 days a year.. As far as I understand, probes have finite lifetime, and counting units (and their upkeep) has its cost.
I always wondered if "smart" traffic lights, which already have some degree of sensing, can help -  at least at highway exits...



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