Interstate systems have evolved to become much more than just routes for distance travel. Some have even called them ‘the Main Street’ of the 21st century, as growth and commerce continue to gravitate toward these corridors. Because they are routinely used for daily travel, congestion has become a common issue,weakening the system’s original intent of moving people quickly along roadways without interruption. The utilization of Ramp Meters to combat this congestion has become more widespread in the U.S.
Ramp Meters smoothes the total flow of vehicles entering a freeway through a process called “access rate reduction.” The process temporarily stores vehicles on ramps and “meters” them or allows access via a signal, at a carefully measured rate. This means that with the added time and distance between the vehicles, the flow onto the freeway does not exceed that interstate’s capacity. This prevents a potential “platoon” of cars, or large group travelling in close proximity, from causing sudden and continued blockages by allowing all cars to merge and enter the flow more easily. Typically, these meters only operate during times of congestion.
Examples of Ramp Metering systems can be found in:
• Illinois: Chicago (this was the first system implemented along the I-290/Eisenhower Expressway in 1963)
• California: Los Angeles, San Francisco and San Diego
• Texas: Dallas, San Antonio, Houston and Austin
• Ohio: Columbus and Cincinnati
• As well as Atlanta, Detroit, Philadelphia, Phoenix, Milwaukee, Kansas City and many other major cities.
In 2010, ABMB completed implementation of Louisiana’s first Ramp Metering system for the LADOTD along the I-12 Corridor from Baton Rouge to Denham Springs. Deemed a major success, ABMB has since been contracted to investigate extending the system to other areas of I-12.
Ramp Metering is a great example of the kind of innovative, sustainable techniques that allow engineers to improve how we use the roads we already have, without adding concrete.