![]() And “queue” loops near the bottom of the ramp tell the system when the ramp is backing up to the point where it could interfere with traffic on the street behind it. “Demand” and “passage” loops near the metering lights let the system know that a car is waiting to enter the highway, trigger the timer that determines when the lights will change, and count the cars entering the highway. This is how the meters know how congested the highway is at any given moment. “Occupancy” loops placed under each highway lane measure traffic speeds by gauging how much time it takes a car to travel a short distance. These loops, as traffic engineers call them, feed data to a computer in a roadside cabinet (the “ramp metering station”). Ramp meters work like that, only with sub-pavement sensors in three different locations. That’s because the lights are controlled by a computer, which is triggered by sensors under the pavement in the turning lane. You’ve probably noticed a fair number of left-turn signals on city streets that remain steadfastly red until a car or two lines up in the left-turn lane. “All the freeways you can think of, they all have ramp meters,” Jreij said. (Appropriately, the center is tucked between an onramp and an offramp.) There are more than 1,000 ramp meters just in Los Angeles and Ventura counties, the area overseen by the Caltrans District 7 transportation management center at the intersection of the 134 and 2 freeways in Eagle Rock. That’s yet another reason not to drive when it rains. Complaints about malfunctioning meters go up when it rains, Jreij said, because vandals and repair crews sometimes leave delicate electronics vulnerable to the elements. When the highway already has more cars and trucks than it can accommodate - hello, Los Angeles! - reducing the number of additional vehicles won’t magically cut commute times.Īnd finally, remember that machines break. Meters do not add or subtract from the number of cars trying to get from Points A to Points B. The second thing is what you might call the Law of Conservation of Vehicle Matter. The meters can’t allow so many cars to back up on the ramp that they interfere with traffic on the roadway behind them. The first thing you have to understand is that the metering system is designed with more than just highway congestion in mind. ![]() Metro is set to release a congestion pricing study this summer that looks at charging people to drive key freeways and roads. ![]() But it might not always be free to drive on For Subscribers The freeway was born in L.A. ![]()
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