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Old July 24th, 2010, 07:46 PM   #21
ChrisZwolle
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Not if there is an enforcement camera next to it...
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Old July 24th, 2010, 08:08 PM   #22
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I had never heard anything about ramp meters before and I already hate them It seems to me that the main goal of ramp meters is to encourage people NOT to use that on-ramp.
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Old July 24th, 2010, 08:50 PM   #23
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In a certain and indirect way, yes. Every road has a speed that yields maximum carrying capacity. If you take a free-flowing freeway at, say, 130 km/h, you can improve capacity by making vehicles driving slower, thus reducing the average distance between each car and moving more cars on a given sector even if each car "eats" lane capacity for a longer period (due to lower speed for the same distance...).

However, past an optimum point, additional reductions in traffic capacity doesn't yield increased carrying capacity because the extra time required to travel is undercompensated by reduced safety distance.

It is quite easy to see it under extreme conditions: it is quite intuitive that distances between cars drop a lot in a highway flowing at 130 km/h to one flowing at 100 (travel time increase = time using the lane = 30%). The distance reduction, though, is far lower from a situation of traffic flowing at 60 km/h to traffic flowing at 30 km/h (travel time increase = 100%).

Therefore, it is in the interest of all drivers using a highway to back up a couple, even a dozen minutes, then have a highway flowing faster. Then, you have an additional positive effect: inducing people who are travelling shorter distances to take other local roads instead of using a freeway for a 4-km trip.
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Old July 25th, 2010, 12:07 AM   #24
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They don't have the same wait times that traffic signals do. They only delay cars maybe one or two seconds at most before they let them proceed. This prevents too many cars from entering the freeway thus causing traffic congestion when they try to merge.


Here is an example on Loop 101 in Phoenix, Arizona.

Last edited by diablo234; July 25th, 2010 at 08:14 PM.
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Old July 25th, 2010, 03:09 PM   #25
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Quote:
Originally Posted by LMB View Post
Are there any laws supporting the "1 auto" sign, or are those to be freely ignored?
Well it's not in the official list, so it might has only informative status. I suspect the lights will just go red fast enough anyway.
I never used one of those entries.
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Old July 28th, 2010, 10:35 PM   #26
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Ramp meter on the entrance to A27 from Houten (Netherlands).

Reportedly, the waiting time can be up to 40 minutes if it is in operation.
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Old July 29th, 2010, 08:42 AM   #27
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They are to common in Washington sate. I-5, SR 520, I-90, I-405 and SR 167
They obviously only work during rush hour but sometimes I get an unpleasant surprise during normal hours + heavy traffic (Friday anyone?).

The problem is that the traffic jams up behind the light and off the highway and that makes the situation worse... At least if you have 2+/3+ people in the car you can go around some of the ramp meters vis HOV lanes
Ill post a video tomorrow

Last edited by Dr.Scope; July 29th, 2010 at 08:52 AM.
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Old July 30th, 2010, 05:38 PM   #29
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What is weird, here in Southern California is a ramp meters are installed on transitions to other freeways/motorways. So you exit a freeway to join another and there is a ramp meter in between.
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Old July 30th, 2010, 08:25 PM   #30
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When I visited Minneapolis a while back I also noticed they had ramp meters at freeway/freeway interchanges. I am not sure if those are effective compared with having ramp meters on interchanges with secondary streets/roads.
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Old July 31st, 2010, 09:35 AM   #31
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Now that just ain't right!
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Old July 31st, 2010, 12:00 PM   #32
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Ramp meters on freeway-to-freeway interchanges are sometimes used in the Netherlands as well. Man, if you need such measures, your freeways are surely out of date!
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Old July 31st, 2010, 07:37 PM   #33
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Quote:
Originally Posted by ChrisZwolle View Post
Ramp meters on freeway-to-freeway interchanges are sometimes used in the Netherlands as well. Man, if you need such measures, your freeways are surely out of date!
If I had more time I could mathematically prove that, over a sufficient long period of time (say, 6-hours of peak summer traffic), the overall carrying capacity of a freeway network is far higher if everyone stays put until they can join the flow near the optimum speed (for current standards, calculated as 88-93km/h on flat terrain, 3m wide lanes for cars in good weather).

Road capacity degrades very rapidly with increasing traffic once they are already saturated. So it pays off to hold even 10% of additional traffic in a small (2-5 km) sector to avoid a heavy flow (all lanes used, 70-90 km/h speed) to become a congestion queue.
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Old July 31st, 2010, 07:54 PM   #34
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The Toronto-bound QEW through Mississauga does:
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Old July 31st, 2010, 07:57 PM   #35
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Quote:
Originally Posted by Suburbanist View Post
Road capacity degrades very rapidly with increasing traffic once they are already saturated. So it pays off to hold even 10% of additional traffic in a small (2-5 km) sector to avoid a heavy flow (all lanes used, 70-90 km/h speed) to become a congestion queue.
The true solution would be to add a lane or two on the motorway, instead of effectively closing it for entering traffic.
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Old July 31st, 2010, 08:10 PM   #36
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And I'd think a freeway-to-freeway ramp meter would just transfer congestion from the road people are trying to get onto to the road they're exiting. So what's the point?
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Old July 31st, 2010, 08:46 PM   #37
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^ Depends how long the ramp is I think.

...but that said, I 'd gather that most metered freeway to freeway ramps would be intelligent enough to have a queue detector that would signal the meters either to move to a faster phasing, or deactivate altogether if the queue got too long.

Just a thought.
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Old April 20th, 2011, 11:01 AM   #38
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An example of a ramp meter instalation in Houston.

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Old April 20th, 2011, 11:05 AM   #39
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http://www.its.umn.edu/Research/Feat...rampmeter.html

A link to the results of a study that was trying to measure how effective ramp meters are at reducing congestion. The study involved shutting off all 433 ramp meters in the Minneapolis-St. Paul area for eight weeks to test their effectiveness. The study was conducted by Cambridge Systematics and concluded that when the ramp meters were turned off freeway volume decreased by 9%, travel times increased by 22%, freeway speeds dropped by 7% and crashes increased by 26%. However, ramp meters remain controversial, and the Minnesota State Department of Transportation has developed new ramp control strategies. Fewer meters are activated during the course of a normal day than prior to the 2000 study, some meters have been removed, timing has been altered so that no driver waits more than four minutes in ramp queue, and vehicles are not allowed to back up onto city streets.
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Old April 20th, 2011, 11:35 AM   #40
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in Seattle they only turn them on during rush hours. It allows 1 car per green (every 5-6 seconds) to enter the freeway and if there is a carpool lane (2+ people in the car) you can enter without having to wait at all


Last edited by Botev1912; April 20th, 2011 at 11:48 AM.
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