Best of Blog: Ramp Metering

We are closing out the year with a Best of Blog collection containing our favorite posts from 2010. This piece, which was one of Ben's favorites, ran on February 3 under the title "Ramp Metering: An Unholy Alliance". The post examines how engineers and planners tend to agree on ramp metering, but for all the wrong reasons. It touches on the quasi-religious beliefs of each profession and, oddly enough, I remember a few angry emails in my inbox after this one ran. We'll see which profession emails me first this time around to inform me that I am ignorant. Send your emails to oleson@strongtowns.org.

Ramp Metering: An Unholy Alliance

When I was in engineering school we made fun of planners. They were out of touch, impractical, idealistic. When I was in planning school we joked about engineers. They were out of touch, unimaginative, rote. These two professions - planners and engineers - are two sides of the same coin, but their approach to solving problems and building communities could not be more different.

Straddling both of these professions (I am both a PE and an AICP), one thing I have always found revealing is how they both (generally) agree on ramp metering. Ramp meters are those mini traffic signals that queue vehicles as they enter the highway. Wikipedia explains their rationale succinctly.

Ramp meters are installed to restrict the total flow entering the freeway, temporarily storing it on the ramps, a process called "access rate reduction." In this way, the traffic flow does not exceed the freeway's capacity. Another rationale for installing ramp meters is the argument that they prevent congestion and break up "platoons" of cars.

The consensus on ramp meters is revealing because it exposes the general failings of each profession in their approach to our common problems of community-building.

In general, planners support ramp meters because they think single-occupancy cars are evil. There are likely some planners reading that sentence in recoil mode, but that is the reality. When we as planners can set up devices that make driving in a car more burdensome, we believe that somehow people will abandon their cars and move to high-density urban Utopias. At the very least, we can give preference to transit systems and people that carpool. Hopefully the "idiots" wasting time and money driving themselves solo to work in their SUV's will grow to understand the benefits of rideshare. And if not, at least they are being punished by having to wait.

In general, engineers support ramp meters because they believe it an ingenious way to solve traffic problems. With ramp meters, you can run more cars through the same pipe in less time. Cut overall travel time, improve safety and make efficient use of highway capacity. Get more out of your system without building any more costly lanes of traffic - it is a level of genius that would make any engineer proud.

Sadly, both professions are wrong about ramp meters.

And not just wrong in their motivation. Even if you hold their motives to be pure, ramp meters actually have the exact opposite result from what each profession is seeking. Let me explain.

In 2000, I was going to graduate school at the University of Minnesota, living in the exurbs and commuting in each day (my wife was driving an equal distance the opposite direction - young and no kids, all seemed fair). My commute was about 50 minutes. I never hit a ramp meter on my way in. I was too far out. But there as I drove by were the lines of cars queued up in the on-ramps, kindly allowing the traffic to flow.

That first semester, the State of Minnesota did a little experiment regarding ramp meters.Wikipedia accurately describes it as follows:

In 2000, a $650,000 experiment was mandated by the Minnesota State Legislature in response to citizen complaints and the efforts of State Senator Dick Day. The study involved shutting off all 433 ramp meters in the Minneapolis-St. Paul area for eight weeks to test their effectiveness. The study was conducted by Cambridge Systematics and concluded that when the ramp meters were turned off freeway volume decreased by 9%, travel times increased by 22%, freeway speeds dropped by 7% and crashes increased by 26%.

Despite the apocalyptic fears from my soon-to-be-planner classmates, their commutes were not snarled in congestion. They were mostly young, lived in the central urban area near campus and had short distances they needed to travel. Now they no longer had to sit at the ramp meters. Many actually indicated that their trip was quicker. 

But for me, those were eight weeks of hell. My 50 minute commute increased to two-and-a-half hours. I sat in congestion for endless stretches. And it is quite simple to understand why.

Before anyone from a first-ring suburb could enter the city, everyone living in the urban core needed to get to where they were going. Since they were uninhibited by metering, they owned the freeways. Once they reached their destination and parked their cars, those from the first ring suburbs could enter the city. The rest of us waited for them to clear out. Then the second ring could enter. Then the third ring. And finally those of us that lived in the exurbs could make our way into the city center.

Planners intent on punishing evil cars and their evil drivers with meters are doing just that. The only problem is, the closer to the city a driver lives, the more they are "punished". Ramp meters make those that live most efficiently - those closest to their place of employment, typically in higher density and in older neighborhoods - wait in favor of those that live the least efficiently. Not exactly what the planners had in mind.

For engineers, the model of efficiency - making better use of the highway capacity through ramp meters on the premise that it saves money - simply allows people to migrate to farther reaches of the system. Volume is up. Travel time is down. Speed is up. Great, but what isn't measured? Vehicle miles traveled. Sure, we may save some money by not having to build more lanes through the inner-ring, but now we have to build miles and miles of lanes in the second ring, third ring and the exurbs, not to mention the ramps, signals and other improvements that go along with that. Measuring the "results" of metering at the meter, engineers miss the overall impact their efforts have on the system. While congratulating themselves for saving millions, they are literallyinducing billions in new demands in other places.

If we are going to grow stronger as a country, we need more from these two professions. Planners need to get real. They need to embrace an approach that is more practical, more empirical and more refined than the simplistic (dare I say, elitist) line of thought that currently dominates the profession. Engineers need to embrace planning and a planner's approach to systems thinking. Building a better mousetrap is novel, but engineers need to ponder whether mice are really the problem and what the consequences of getting rid of them are. "Got hammer, find nail" is growing us into decline. We need to get smarter.

Ramp metering, and similar schemes, need to be replaced with a Strong Towns approach. The way to bring about a more efficient development pattern is not to try and "punish" the symptoms of bad development (talking to you, planners) but to instead stop subsidizing inefficiency. The way to get more out of our transportation system and reduce congestion is not more capacity (talking to you, engineers) but through strengthening neighborhoods and using mixed-use zoning to reduce trips.

Do more with less. Build better places. Stop sitting at ramp meters. That's Strong Towns.