Ramp Meters

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.

The following table lists active ramp metering areas in US metropolitan areas. Comments and corrections are always welcome at froggie@mississippi.net. The list is alphabetical by state:

Metropolitan Area	Routes	System
Phoenix, AZ	I-10, 17 US 60 AZ 51, 101, 143, 202	Apparently pre-set
Greater Los Angeles, CA	I-5,10,105,110,210,405,605,710 US 101 CA 22,30,55,57,60,71,91,110,118,134 Others?	Unknown
Fresno, CA	CA 168, 180 CA 41? Others?	Unknown
Sacramento, CA	I-5, I-80, BL 80, US 50? CA 99	Unknown
San Francisco, CA	I-238, 880 CA 85 Others?	Unknown
San Diego, CA	I-5, 15, 805 CA 52, 94	Unknown
Santa Rosa, CA	US 101	Unknown
Denver, CO	I-25, 225, 270 US 6 C-470	Unknown
Atlanta, GA	I-75	Unknown
Chicago, IL	I-90, 94, 290	Unknown
Baton Rouge, LA	I-12	Unknown. Activated November, 2009.
Detroit, MI	I-75, 94 M-10	Unknown
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 US 95	Several turned on in early 2007. Operated by FAST (part of the Las Vegas MPO).
Long Island, NY	I-495 Northern State Pkwy Southern 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?
Columbus, OH	I-70 OH 315	Unknown whether they are in use or not
Portland, OR	I-5,84,205 US 26 OR 217	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
Houston, TX	I-10, 45, 610 US 59, 290 TX 225	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
Milwaukee, WI	I-43, 94, 894 US 45	Unknown
Seattle, WA	I-5, 90, 405 WA 167, 520	All but 3 are centralized.
Sydney, Aus.	M4, SR 40	Unknown
Toronto, ON	QEW	Centralized
Birmingham, UK	M6	Unknown
Southampton, UK	M3, M27	Unknown, but uses detector loops in the pavement.

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:

There are a few metropolitan areas I know of that are considering ramp meters in the future:

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.

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.