Ramp Metering

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Is It Time for Ramp Metering in Indianapolis?

The answer to this question should be a resounding yes. Why may you ask.
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Look at the congestion on area freeways that congregates around the area freeways entrance points. These are growingly becoming more and more dangerous as people dart over several lanes in order to avoid the slower traffic in the right lanes. Metering traffic on the onramps can help alleviate this by distributing the oncoming flow of traffic more evenly onto the freeway at a more controlled rate and thereby reduce the amount of slowing in the right lanes and general slowing altogether and thusly improve safety and reduce collisions. Will it eliminate slowdowns altogether, no but it will have a significant positive impact and mitigate some of the negative impacts of weaving and cutting in caused by overcrowding at the acceleration lanes.

Extensive Use Around the United States

Ramp Metering signal technology has been in use in most major metropolitan areas all over the United States. According to Wikipedia "Ramp metering was first implemented in 1963 on the Eisenhower Expressway (Interstate 290) in Chicago. Since then ramp-meters have been installed in many urban areas including many cities in California; as well as Philadelphia, PA; Seattle; Denver; Phoenix; Las Vegas; Salt Lake City; Portland; Minneapolis-St. Paul; Milwaukee; Columbus; Cincinnati; Houston; Atlanta; Miami; Washington, DC and Kansas City, MO". These signals have served to help mitigate the slowdowns that unrestricted flow from onramps causes on freways.

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How They Work

A Upstream loop sensor monitors traffic on the mainline lanes of the freeway and based on the traffic volume sends data to a computer controlling the signal timer that controls the metering signal that releases the vehicles at a set rate in time with traffic. With smart or intelligent traffic systems technology this release rate can be adjusted accordingly based on traffic demand and congestion. And in the future with changeable signage could potentially allow for release of one, two or three vehicles per green based on demand.

Advantages

Mitigation of Congestion

Due to their metering capacity and ability to release traffic at a regulated rate they help to spread out traffic into a more sustainable pattern that is more readily able to integrate into existing traffic without the rapid braking that leads to backups and traffic jams. While this is not a perfect solution the results are much more favorable than not.

=Useful as a solution to managing traffic

This is especially true when used with other intelligent trasportation systems such as smart roads and lane controls and variable speed limits. These responsive solutions that respond to the congestion have been useful in places like the UK on their motorways to help reduce the number of collisions and even the occurrence of traffic jams.

Drawbacks

Queues

One of the drawbacks is the long queues that can build up for vehicles waiting in queue to enter the freeway at a metering signal. At times this can lead to traffic backing up into the intersection at the surface street or the connecting road. This has been a common issue reported and comes down to a couple of factors endemic to a greater problem than metering signals can resolve on their own. This indicates poor road design or insufficents through capacity that needs immediate resolution. This has lead to some cities disabling some or all of their metering signals. A move that in the greater scheme of things is short sighted given the greater benefit that metering creates. Metering signal timing can be adjusted to help with this situation as a temporary solution but the greater issue causing this must be resolved to prevent further gridlock.

Cannot Correct Major Congestion Issues

Ramp metering is not intended to be a replacement for other types of traffic congestion releif such as building additional travel lanes along major highways thereby increasing traffic volume. Once volume is increased, systems like Ramp HOV lanes, ramp metering, and lane control systems help enhance the flow on these existing roads helping them to operate better than they would otherwise.