How is it that ramp metering is just entering my life, at least in a routine way, in the year 2016? I’ve lived and commuted around the Washington DC area since 1999 and, with a recent move, I am just now getting exposed to this wonderful invention. It turns out, it’s been around for decades. But why is not used everywhere?
What Is It?
The Department of Transportation defines it as “traffic signals installed on freeway on-ramps to control the frequency at which vehicles enter the flow of traffic on the freeway“. Basically it keeps the main flow of traffic from being continually interrupted by droves of cars all merging at the same time. This ends up backing up both the main artery and the feeder lane(s). They even have a handy image to dumb it down for us.
You can continue to read through their content for lots of metrics, charts, and graphs about how amazing it is. I was going to reiterate some of that here, but got incredibly bored by it all and couldn’t be bothered. Suffice to say, the data shows that it works. Which makes common sense, any road that has a continuous run of traffic entering it will be more congested than one that has a more metered approach.
See what I did there.
Ramp metering started out as a simple police officer standing along an on-ramp and allowing traffic to take off at a set interval. Sounds like an assignment for someone who lost their temper on a bus full of school kids, or a fast food clerk.
It has eventually evolved into a pretty intelligence system, as you can see above, featuring demand control algorithms and other things I’m not all that interested in discussing here.
Sorry, that was a pretty lame history lesson, suffice to say many major cities use ramp metering. With the exception of Houston, most major Texas cities (including Dallas) have implemented, and removed, ramp metering. Perhaps it was too confusing for Cowboy fans.
My favorite part of ramp metering, it’s basically legal drag racing. My entrance onto 395 in Virginia consists of (2) lanes, much like the image below. Except…both lanes go on green. You creep up to the sensor and, while the light doesn’t quite drop like the tree at your local 1/4 mile strip, you still get to test your mettle against other commuters on green. It’s good fun.
Why Not Everywhere?
So why don’t all cities use ramp metering? Well, it’s not free, but the DOT outlines the costs of previously implemented systems and it’s not that expensive. Especially compared to other initiatives that our city managers spend our money on. What annoys me, as a commuter in what is widely regarded as one of the (if not the) worst commuting regions in the country, is that ramp metering is only used on two roads in the DC area, Interstate 395 and Route 66.
So indeed DC, Maryland and Virginia, why not everywhere?
In the future, it may not matter. Fully autonomous systems should be able to calculate merging speeds and distances between vehicles to just slide you right in to traffic while you surf YouPorn. This neat video shows some of the potential benefits of future tech in keeping us moving. And I’m already on record saying that I, for one, welcome our autonomous overlords!