This is a quick-and-dirty page I threw up in response to a thread on the Misc Transport Road newsgroup regarding ramp metering. What I've done is set up a page that lists which highways in which metropolitan areas have ramp meters. If you have any corrections for me, PLEASE let me know. For the record, personally, I am VERY MUCH in support of using ramp meters. I have seen them in action and know that they work.
A ramp meter is a set of traffic signals located on a freeway entrance ramp, usually located about halfway down the ramp. In most respects, it functions exactly like a normal traffic light. Their main purpose is to control traffic flow onto the freeway, in order to improve efficiency of the freeway itself. Studies have shown that ramp metering, when used properly, can reduce accidents, improve freeway speeds, and improve freeway capacity.
Most ramp meters are timed to allow one car per green light cycle. The timing system between green cycles is either preset at a specified time, or is tied to a centralized system that utilizes real-time traffic data and adjusts the cycles accordingly. The ramp meters themselves vary depending on location, from Chicago's simple green-light/red-light to Minnesota's mounting one standard (red-yellow-green) traffic light on top of another.
For more information on ramp metering, look up the Minnesota Department of Transportation's Traffic Management Center website. MnDOT also recently completed a ramp meter study.
Ramp Meters in the US
The following table lists active ramp metering areas in US metropolitan areas. Comments and corrections are always welcome at firstname.lastname@example.org. The list is alphabetical by state:
AZ 51, 101, 143, 202
|Greater Los Angeles, CA||I-5,10,105,110,210,405,605,710
|Fresno, CA||CA 168,
|Sacramento, CA||I-5, I-80,
BL 80, US 50?
|San Francisco, CA||I-238,
|San Diego, CA||I-5, 15,
CA 52, 94
|Santa Rosa, CA||US 101||Unknown|
|Chicago, IL||I-90, 94, 290||Unknown|
|Baton Rouge, LA||I-12||Unknown. Activated November, 2009.|
|Twin Cities, MN||I-35E,
35W, 94, 394, 494, 694
US 10, 12, 52, 169, 212
MN 36, 62, 77, 100
|Most are centralized from MnDOT's RTMC. A few are still pre-set stand-alones.|
|St Louis, MO||I-64||Unknown|
|Las Vegas, NV||I-15, 515
|Several turned on in early 2007. Operated by FAST (part of the Las Vegas MPO).|
|Long Island, NY||I-495
Northern State Pkwy
|Operated by INFORM.|
|New York, NY||I-678||Unknown|
|Cincinnati, OH||I-74||Unknown. Activated November, 2009.|
|Cleveland, OH||I-71||Not activated yet?|
|Unknown whether they are in use or not|
|Sensor loops and preset timers, apparently.|
|Lehigh Valley area, PA||US 22||Operated by PennDOT. Type of ramp meter unknown.|
|Philadelphia, PA||I-476||Operated by PennDOT. Recently reactivated.|
|Arlington, TX||TX 360||Unknown|
US 59, 290
|Operated by TxDOT's TranStar. Apparently are centralized.|
|Salt Lake City, UT||I-15||Unknown|
|Arlington and Alexandria, VA||I-66, 395||Unknown|
|Madison, WI||US 12/18 (Madison Beltline)||Unknown|
|Seattle, WA||I-5, 90,
WA 167, 520
|All but 3 are centralized.|
|Sydney, Aus.||M4, SR 40||Unknown|
|Southampton, UK||M3, M27||Unknown, but uses detector loops in the pavement.|
Ramp Meters come and gone?
The following is a list of metropolitan areas that have had ramp meters in the past, but do not appear to have any active ones now:
San Antonio, TX
Ramp Meters to come?
There are a few metropolitan areas I know of that are considering ramp meters in the future:
Des Moines, IA
United Kingdom Ramp Meters
Ramp metering is also being tested in the UK. This website details the ramp metering test currently underway on the M3 and the M27 in and near Southampton, UK. I also have an E-mail from the head of the UK ramp meter testing team, from April 2001.
According to the Brits, ramp metering is also used in France and Holland, although I have no further information on the status in these two countries.
Down Under Ramp Meters
There are even ramp meters in Australia. One is on the westbound onramp from SR 61 to the M4 Motorway, the other is from Victoria Rd (SR 40) to the Glebe Island Bridge (also SR 40). Thanks to Dan Moraseski and Brad Torr for pointing these out.
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Page last modified 18 November, 2009