End the Carpool Madness – A Plea for Sanity

Despite their laudable their goals, carpool lanes must be recognized as a failure, and other options considered.

Originally published 2002

It’s time we recognized carpool lanes as the failed experiment they are, and move on to other ideas. I’m going to support that notion in a moment with what I trust will be convincing arguments, but first let me make clear that I an totally in favor of the goals they were intended to achieve.

I applaud people on bicycles and those who use other forms of human-powered locomotion. Each of them represents on less car on the road, that much less pollution in the air. I appreciate the people with the patience to use mass transit systems, for the same reasons. Along those lines, see  Mass Transit: The Way it Ought to Be.

I also love community-building ideas. One of my favorite vacations is Lark Music and Dance Camp, held in a redwood forest in Mendocino. One of the best parts of that experience is that I don’t go anywhere near the car for an entire week. Driving down the country roads at the end of the week, I notice how relaxed and easy going I am. It is only when I get back to civilization that I re-experience the tension I live with most every day.

I’ve written up a few community-building ideas in Building a Community with Music and Dance. But here, we’re talking about the evils of carpool lanes. So let’s get on with it.

Defining the Goal

The whole point of carpool lanes was to reward people who carpool by giving them an easier ride. We like the carpooling concept, so we want to encourage it. Carpooling reduces the number of cars on the road, uses up less gasoline, and generates less pollution. The question is, are carpool lanes the best way, or even a good way, to achieve that goal.

Carpool lanes have been operating for many years now. It’s time to take a hard look at how well they have achieved their goals.

Measuring Effectiveness

The only truly effective measurement for the value of carpool lanes is this: How many people are in multiple-occupancy vehicles who would not otherwise be doing so? The highlighted part of the question is important. The measure is not, and cannot, be the number of multiple-occupancy vehicles. The question is, how many cars have we gotten off the road?

Admittedly, it is difficult to get an exact answer to that question. But if you take a look at who’s in the carpool lane the next time you drive, you can make an educated guess.

To answer that question, let’s take a look at some of the people we typically see in the car lane:

  • A single mom or dad with their kids
    How many cars is that vehicles is that particular “carpool” saving?
  • A bunch of suits on their way to or from the airport
    The fact of the matter is that when a large company sends a group of people out to a conference or a meeting, they only get one car. It saves expenses, and no one has separate destinations anyhow. Even a single traveler may well be picked up by someone at the local office. So those multiple-occupancy vehicles going to and from the airport — or even to and from a meeting — or quite liable to have been multiple-occupancy vehicles in any case.
  • A utility truck
    There’s a couple of guys in a gardening truck, or in a electric utility van. They’re riding together out of necessity, of course. We’re not saving any vehicles there.
  • A motorcycle or two
    Of course, motorcycles can use the carpool lane. But in California they can ride between the lanes, too. When traffic is really tight, that saves a lot more time than the carpool lane. When traffic is moving, they often can’t keep up with high speeds safely, anyway, so their are very few of them in the carpool lane, at any given time.
  • A husband and wife
    Here is another pair that would probably be riding together anyway. Their destinations must be near one another. And presumably they like each other. They ought to. They’re married! So we’re not saving a vehicle on this one either.

Now, some of those pairs that look like “husband and wife” couples may consist of people who are not actually related. But many of them surely are. Or they will be. After all, if they like each other well enough to ride together, well, one thing leads to another. Such couples would be riding together anyway, so there are no savings there, either.

Every so often, you so a couple of people who look like they might actually be carpooling. Yay! But we have to ask, how many of those good souls are there? And how many of them are so socially conscious that they would be carpooling anyway, for the sake of the environment?

Again, a precise measurement is difficult to obtain. But it is clear that the number of people who are carpooling, who would not be carpooling anyway, is a pretty small fraction of the people who are in the carpool lane.

In a moment, we’ll look at the enormous costs associated with having a carpool lane. At the point, it will become quite clear that that value of carpool lanes are drastically outweighed by their costs.

That’s not to say that carpool lanes were an unwise experiment, however. It was a risk well worth taking. Had they worked out, they would have been great. However, the data is in now. It is possible to declare in hindsight what we could not reliable predict in advance — namely, that they are an environmental disaster.

Electric Vehicles

Before we go on to look at the costs of carpool lanes, it makes sense to say a word about electric vehicles.

Would there were more of these! It almost makes sense to keep carpool lanes for just that reason. But that is a really bad argument because:

  1. The incentives to save gasoline and be good to the environment, coupled with the tax advantages and the financial capability to make such a purchase, probably factor more into the buying equation than the existence of carpool lanes.
  2. At this point in time, such vehicles are only practical for short hauls, and won’t be comfortable in the carpool lane when traffic is running normally.
  3. At some point, when the costs of ownership the scales of ownership in favor of buying an electrical vehicle, everyone and his brother will be trying to crowd into the carpool lane. At that point, the carpool lane will confer no particular advantage. The privilege of using it might even have to be revoked, to preserve it for multiple-occupancy vehicles!

Calculating the Cost

Carpool lanes incur two significant, interrelated costs:

  • time
  • pollution

The Time Cost

Carpool lanes significantly increase the amount of time that vehicles are on the road. That fact, by itself, increases the amount of pollution attributable to automobile exhausts.

To get a feeling for how much time is being consumed by carpool lanes, take at look at what happens at the end of carpooling hours. Within 10 minutes, traffic is suddenly flowing freely. Within 20, it has all but vanished from the road.

Do we imagine that people have somehow magically timed their driving times so that they are all pulling off the road to their destinations right at the end of carpooling hours? Doubtful. The alternative explanation is that the carpool lane creates a bottleneck that restricts the flow of traffic. Like an accident that closes off a lane, the carpool lane forces more traffic into fewer lanes. That makes things slow down.

There are two reasons that carpool lanes slow down traffic. One is simply the fact that, during carpool hours, the number of available lanes is reduced by a fourth, or even by a third. The net effect is that the best design of traffic planners are defeated. They carefully built the roads wide enough to accommodate the amount of traffic they predicted, by the number of lanes they provided were removed by legislative fiat.

Second, even though a 1/4 or 1/3 reduction doesn’t seem like much, it has a major impact on maneuverability.

The importance of maneuverability rests on another observation: At the head of every long line of traffic, there is a “moving cork”. A moving cork consists of a vehicle that is going the same speed as the vehicle in the adjacent lane, with traffic that wants to move faster behind it. When the driver of such a vehicle is too witless or too inconsiderate to speed up or slow down so they pull over to let faster vehicles pass, they effectively cork the highway, and force everyone to travel at their speed.

California was wise enough to pass a law which requires anyone with 5 or more vehicles behind them to pull over. But that law was passed with mountain roads in mind, and it is rarely enforced in any case. (If it were enforced more widely, it would no doubt have an expeditious effect on traffic!)

To see the effect of such a “cork” on traffic, imagine a one lane highway with 5 cars going at different speeds. If the fastest car is first, with the next fastest behind it, and so on then, in effect, everyone has the road to themselves. They all get to their destination at the rate that they expected to be travelling.

Now put them on the road in reverse order. If the slowest car is first, and the next slowest is behind, and so on, then only one car on the highway is traveling at the speed they want to go. The other four are delayed, at best, and frustrated no end, at worst — especially if slower cars never pull over for faster ones.

That’s why really good, conscientious drivers glance into their rear views from time to time, and pull over when someone faster is behind them. Doing so helps to create the best possible ordering of vehicles with respect to their speeds. Of course, they also try to be patient when someone ahead of them is going more slowly.

But no matter how easy going you usually are, there are times in this overly fast-paced society that you need to get where you’re going in a hurry. At such times, a “cork” can be a frustrating inconvenience that severely degrades your perceived quality of life.

Additional lanes provide the ability to maneuver around such cars. They also make for greater distances between cars, which makes it easier to pull over when you need to. It is for that reason that losing a 1/4 or 1/3 of the lanes on the road makes such a difference in drive time.

The Pollution Cost

But in addition to keeping cars on the road for longer periods of time, carpool lanes also reduce speeds to some of the worst possible levels for operating efficiency. At a slow crawl, very little of the gasoline burned goes into forward movement. Instead, it goes into heating the brake pad the driver uses to hold back the vehicle’s speed.

Instead of operating in a high gear, and covering 50 miles for a gallon of gasoline, the vehicle is in a low gear, and may only cover 10. The gallon of gasoline is still burned, however, and the amount of pollution generated by that gallon of gasoline is the same. Only you’re burning five times as much, so you are generating five times as much pollution.

Maybe, and it’s a big maybe, carpool lanes have done us a favor by making the problems of traffic jams inherent that much sooner. Perhaps the fact that people are sitting in long lines of traffic, inhaling each others fumes, has caused them to be more in favor of electric vehicles.

But it’s a big maybe. If affordable, usable alternatives actually existed, they would be in a lot wider use. The fact is, we’re still grappling for a solution. Meanwhile, the existence of high-density, high-cost, low-quality-of-life population centers has meant that people continue moving out to the suburbs to build a life, while commuting into the city to make a living. (For some alternatives to that scenario, see Mass Transit: The Way it Ought to Be and Building a Community with Music and Dance.)

The costs, in the meantime, have been staggering. Huge amounts of gasoline burned, with no one going anywhere. Huge amounts of pollution generated. The impact on health that results from breathing the fumes. Lost time, lost productivity, lost time with family and friends. Increased frustration and stress. Reduced quality of life.

When we compare the costs of carpool lanes with the measurable benefits, it is fairly easy to see that carpool lanes have done little to fulfill their hoped-for promise.

Looking at Alternatives

But carpooling is still a good idea! There is no argument about that. The issue is only whether carpool lanes have been effective, and whether their benefits outweigh their costs. The answer to each question is pretty clearly, “No”. But that does not mean we should give up searching for ways to promote carpooling.

One such alternative is the elimination of tolls for multiple-occupancy vehicles. Where bridges and tunnels have adopted such a policy, ad hoc “rider congregations” have cropped up. A driver can stop at such an area, pick up a rider or two, and sail across the bridge without having to pay a toll. Once across, they drop off their passengers at a similar point on the other side.

That system works for everyone. Bridges and tunnels form “choke points” that are often difficult to service with mass-transit vehicles. That makes it hard for people to use mass transit, even when they would otherwise do so. In addition, the amount of traffic that goes across a bridge generally means a very short wait for a ride. (On the other hand, the otherwise good idea of only charging a toll one way across a bridge or tunnel may make it hard for the rider to get back!)

And unlike the typical carpool lane, many of the vehicles going across the bridge really are multiple-occupancy vehicles. On average, each such vehicle represents one less car on the road. (Some may represent 2 or 3 cars off the road, others may represent none.) And they average one less car right where it counts — at a major choke-point that would otherwise increase delays, gasoline consumption, and pollution.


While carpooling is a great idea, carpool lanes are horribly ineffective at promoting it. There is no clear indication that the number of carpooling people who would not otherwise be carpooling is increased by the existence of carpool lanes. But there are very real costs: increased commute times, increased gasoline use and pollution, health impacts, lowered productivity, and lessened quality of life.

In short, carpool lanes must be recognized as the failed experiment they are, and abolished. Other alternatives must be used to achieve the goals that carpool lanes were intended to achieve.

Copyright © 2002-2017, TreeLight PenWorks

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