Would you use a rototiller to get rid of weeds in a flowerbed? Of course not. You might solve your immediate goal of uprooting the weeds — but oh, my, the collateral damage that you would do.

Yet when we try to eliminate congestion from our urban areas by using decades-old traffic engineering measures and models, we are essentially using a rototiller in a flowerbed. And it’s time to acknowledge that the collateral damage has been too great.

Image: Andy Singer

Image: Andy Singer

First, an explanation of what I call the “deadly duo”: travel projection models and Levels of Service (LOS) performance metrics.Travel projection models are computer programs that use assumptions about future growth in population, employment, and recreation to estimate how many new cars will be on roads 20 or 30 years into the future.

Models range from quite simplistic to incredibly complex and expensive. Simple models deal primarily with coarse movements of vehicles between cities, while complex models deal with the intricacies of what happens on the fine grid of urban areas. To be truly accurate, growth projection modeling can be expensive. Therefore, absent compelling reason to do otherwise, most growth projections tend to be done using less expensive techniques, which usually lead to overestimates.

Levels of Service (LOS) is a performance metric which flourished during the interstate- and freeway-building era that went from the 1950s to the 1990s. Using a scale of A to F, LOS attempts to create an objective formula to answer a subjective question: How much congestion are we willing to tolerate? As in grade school, “F” is a failing grade and “A” is perfect.

Engineers decided that LOS “C” was a good balance between overinvestment in perfection and underinvestment leading to congestion. In urban areas, a concession was made to accept LOS D, representing slightly more restricted but still free-flowing traffic. LOS is commonly (actually, almost always) calculated using travel projections for 20 to 30 years into the future.

Using basic traffic models and LOS C/D to plan and design the interstate system was a no-brainer in the 1950s, ’60s and ’70s. When deciding how many lanes to build on a freeway connecting major cities, a sensitivity of plus or minus 10,000 trips a day could be tolerated, and the incremental difference in cost to plow through undeveloped land was relatively insignificant.

Good approach, wrong setting

I’m not going to look back and quibble with the general philosophy of how the interstates and the associated high-speed freeways were planned and designed. On many levels, the approach made sense.

But it became increasingly less persuasive when applied to the rest of our road network. Unlike interstates and freeways, most roads exist not just to move traffic through the area, but also to serve the homes, businesses, and people along them. Yet in search of high LOS rankings, transportation professionals have widened streets, added lanes, removed on-street parking, limited crosswalks, and deployed other inappropriate strategies. In ridding our communities of the weeds of congestion, we have also pulled out the very plants that made our “gardens” worthwhile in the first place.

It’s worth remembering, too, that not all congestion is bad. John Norquist, former Mayor of Milwaukee and current CEO and President of the Congress for New Urbanism, suggests that congestion is like cholesterol: there is a good kind and a bad kind.

What makes the prevailing situation even more troubling is that there are no comprehensive requirements dictating the use of either LOS or travel modeling in transportation planning and project design. The “Green Book” from the Association of American State Highway and Transportation Officials (AASHTO) (more formally known as “A Policy on Geometric Design of Highways and Streets”) clearly states that these are guidelines to be applied with judgment — not mandates. So does the Federal Highway Administration’s “Highway Capacity Manual.”

The idea that we must rid our roads of any and all traffic congestion is, in fact, a self-imposed requirement. As Eric Jaffe wrote in an article for Atlantic Cities in December, 2011:

Although cities aren’t required to abide LOS measures by law, over the years the measure hardened into convention. By the time cities recognized the need for balanced transportation systems, LOS was entrenched in the street engineering canon.

Worse yet, many designers size a road or intersection to be free-flowing for the worst hour of the day. Sized to accommodate cars during the highest peak hour, such streets will be “overdesigned” for the other 23 hours of the day and will always function poorly for the surrounding community.

If that isn’t troubling enough, LOS is often calculated using traffic predicted 20 years into the future, even in urban settings. Until the forecasted growth materializes, the roadway will be overdesigned, even during the peak hour. Overdesigned roadways encourage motorists to drive at higher speeds, making them difficult to cross and unpleasant to walk along. This degrades public spaces between the edges of the road and the adjacent buildings, encourages people to drive short distances, and generally unravels a community’s social fabric.

Let me repeat: Contrary to what you may hear, there is no national requirement or mandate to apply LOS standards and targets 20 years into the future for urban streets. This thinking is a remnant from 1960s era policy for the interstate system, and has erroneously been passed down from generation to generation.

Image: Andy Singer

So what are the right approaches?

Asking the simple question, “Do you want congestion reduced at a particular location?” is a question out of context. It’s like asking you whether you want to never be stung by a bee again. Of course, the answer will be yes. But what if I told you that to in order to never suffer a sting again, every plant within a several mile radius would have to be destroyed — and that you could never leave the area of destruction?

You would have a completely different answer, I’m sure.

The question that needs to be asked in urban settings is not whether you ever want to sit in congestion again. Who does? The question is whether you want to eliminate congestion on your Main Street 24 hours a day, 7 days a week, 365 days a year — knowing that the consequence would be a community with decimated economic and social value, increased reliance on car use, increased crashes, and, ultimately, more congestion.

Recognizing the need for balance, a number of entities are beginning to promote approaches sensitive to the context.

I was the New Jersey Department of Transportation’ s project manager for the “Smart Transportation Guide” (STG), adopted jointly by the state DOTs in Pennsylvania and New Jersey. The STG directs DOT designers to consider the tradeoffs between vehicular LOS and “local service.” It goes on to say that if the street in question is not critical to regional movement, that LOS E or F could be acceptable — and that designers may actually need to design to slow down cars.

The Institute of Transportation Engineers, an “international association of transportation professionals responsible for meeting mobility and safety needs” also promoted this concept in its landmark “Context Sensitive Solutions Guidelines for Urban Thoroughfares.” Florida DOT has adopted multimodal LOS standards, and cities like Charlotte, N.C., have elevated pedestrian and bicycle LOS to the level of that for automobiles. We have a long way to go, but the door is opening.

Creating balanced standards for roadway design will benefit transportation as well. In the Netherlands, the “Livable Streets” policy led to a remarkable improvement in safety on their roadways. They started in the 1970s with a crash rate 15 percent higher than in the U.S., and now have a crash rate 60 percent lower.

Design with the community in mind

It’s time for communities and transportation professionals alike to accept that we have been using the wrong tools for the wrong job. LOS and travel modeling may be effective when sizing and locating high-speed freeways, but are totally inappropriate in every other setting. If travel modeling with high rates of growth is used to make street decisions, your community may be doomed to a series of roadway widenings or intersection expansions. If vehicular LOS C or D performance measures are adopted as non-negotiable targets, major road construction will be heading your way.

Village, suburban and city streets need to be designed with the community in mind using the PPS principle of Streets as Places to create a vision for a great community and then plan your streets to support that vision.

Lets not be fooled by the appearance of science behind Levels of Service and Traffic Modeling. As I pointed out in an interview with Wayne Senville that was published in the November 2010 “Planning Commissioner’s Journal,” LOS standards are easy to understand — and that’s exactly what makes them so dangerous.

As part of the grand bargain struck between Mayor Michael Bloomberg and Governor Andrew Cuomo that will create a new class of hail-able livery cabs, NYC will auction off 2,000 new yellow taxi medallions. The city is expected to haul in a billion dollars from the auction, but Komanoff calculates that in the bargain, central Manhattan streets will be overrun with even more traffic:

No one mentioned traffic when the taxi deal was rolled out last month at City Hall and in Albany. After all, with 800,000 motor vehicles already entering the Manhattan Central Business District (CBD) each weekday, what difference could a mere 2,000 additional yellow cabs possibly make?

Plenty, it turns out. Yellow cabs spend three-fourths of each shift, around seven hours, plying CBD streets and avenues. (And of course some are active for two shifts a day.) Most private cars driven in Manhattan don’t do so for long. Even at the CBD’s notoriously labored traffic pace — now averaging 9.5 mph, up from 8 mph before the recession — the two to three miles per day logged by the average car below 60th Street occupy 15 to 20 minutes.

Adding one new medallion is thus equivalent to adding 40 private cars. Adding 2,000 of them — as the City now intends to do during the next three years — would be the traffic equivalent of adding 80,000 cars, a 10% increase in volume.

Some form of congestion pricing would be just about the only way to mitigate the impact of all this additional traffic, Komanoff writes. You can see the analysis underlying his conclusions in this PDF.

According to the 2011 Urban Mobility Report, released today by the Texas Transportation Institute, this delay cost the average D.C. driver $1,495 once you factor in lost productivity and increased trucking times. In Chicago, it’s $1,568. L.A., $1,334.

Every year, TTI puts out their Urban Mobility Report, and every year we criticize it for its autocentrism. After all, its sole measure is how fast a vehicle can speed down a given mile of roadway. Maybe your city is dense and friendly to pedestrians and bikes, so that it’s easy to glide past the automobile gridlock on your short commute to work. Or maybe transit provides an excellent and affordable alternative to traffic jams. None of that matters to TTI. If someone, somewhere, is sitting in traffic, that’s all that matters. All other measures and modes of urban mobility are ignored.

TTI doesn’t bother to figure out how much time is saved if one avoids that congestion by taking transit, but they do examine how much time transit riders save drivers by taking vehicles off the road.

How public transportation reduces delays for drivers, 2010. Source: 2011 Urban Mobility Report, via APTA.

If there were no transit, the country’s drivers would be facing an additional 796 million hours of traffic delay. (Take that, drivers who grumble when their gas tax “user fee” funds mass transit!)

“Operational treatments” like ramp metering, traffic light timing, and removing crashed vehicles from the road have become much more effective in the last 20 years but still don’t come close to the savings provided by transit, saving about 40 percent as much as transit in terms of hours of delays, fuel, and costs.

Still, in TTI’s examination of congestion relief strategies, public transportation is barely alluded to and never mentioned outright, while operational treatments get significant attention. There is a shout-out to smart growth, or “denser developments with a mix of jobs, shops and homes, so that more people can walk, bike or take transit to more, and closer, destinations.” They also suggest telework and, of course, adding capacity.

TTI warns that congestion is only as bad as it is because the economy is still sluggish. We can expect a rapid worsening of the situation when the economy rebounds – 3 more hours of delay by 2015 and 7 hours by 2020, per commuter, with costs rising from $101 billion to $133 billion, more than $900 for every commuter, and enough wasted fuel to fill more than 275,000 gasoline tanker trucks.

I guess it’s time to really get to work on expanding and improving transit service then; right, TTI?

[T]he future of New York’s cash-poor transit system, depended on by millions of riders a day, has now fallen directly to Mr. Cuomo, who must pick a successor.

The passage is spot on, but for this missing note: The city and region’s 8 million train, bus and subway riders aren’t the only people who depend on public transit. So do a million or more daily motor vehicle users, who will find themselves in ever-worse gridlock if fare hikes and under-investment lead even a small fraction of transit passengers to switch to automobiles.

How much worse will traffic congestion get if transit deteriorates? A lot, potentially. Consider a combination of higher fares and reduced service sufficient to bring about a 5 percent decline in subway use, so that weekday trips by subway to the Manhattan Central Business District, currently averaging 2,160,000 a day, shrink by 110,000. My modeling suggests that while a majority of those trips will relocate or simply disappear, an estimated 35,000 of them will continue to be made, in cars.

Auto trips to the CBD will increase in this scenario by nearly 30,000, allowing for cars with more than one person. While numerically that increase is much smaller than the drop in subway use, the increased volume of traffic will depress already abysmal travel speeds in the Manhattan core by more than 4 percent and slow traffic on the CBD approaches by an average of 1-2 percent. The estimated “time costs” of these new delays: nearly $600 million a year.

Is this scenario realistic? Sadly, yes. According to my travel-and-traffic modeling, it wouldn’t take much in the way of fare hikes and service cuts to bring about a 5 percent cut in subway trips. Here’s one way it could happen:

Raise fares (generates $230 million)

• Raise price of unlimited-fare Metrocards by 10 percent
• Eliminate current 7 percent bonus on $10 or higher pay-per-ride Metrocards

Cut service and investment (saves $440 million total)

• Cut $40 million from subway operations
• Cut $400 million a year from MTA capital program

The above combination is all it would take for 5 percent of subway riders to bail and collectively put 30,000 more CBD-bound car trips on the road. Now let’s add up this scenario’s pluses and minuses.

Pluses: Transportation authorities gain $560,000,000 a year

• MTA cost savings: $440 million
• MTA revenue gain: $90 million ($230 million from fare hikes, less $140 million from decreased ridership)
• MTA and Port Authority toll windfall (from increase in tolled tunnel trips): $30 million

Minuses: Public loses $995,000,000 a year + other uncalculated costs

• Motor vehicle users’ time losses from increased congestion: $590 million
• Transit users’ time losses from service cuts: $170 million
• Environmental costs (more pollution, crashes, noise, etc.): $135 million
• Lost longevity as heavier traffic discourages biking and walking: $100 million
• Job losses from increased congestion and cutbacks in transit operations and improvements: ??
• Lost economic activity from fewer person-trips to the CBD: ??

For every dollar saved by the MTA, the resultant drop in subway usage costs city and suburban residents nearly $1.80 in time, health and quality of life, with drivers’ lost time alone ($590 million a year) more than offsetting the MTA’s net gain ($560 million). And this accounting, which holds across a range of scenarios, omits costs due to lost employment and commerce.

From an overall societal standpoint, then, transit disinvestment is a big loser — a point that Dick Ravitch, Ted Kheel and other civic leaders labored for decades to get across to both City Hall and Albany. Ironically, many of the folks with the most to lose never even swipe a Metrocard.

The Chamber of Commerce report states that American transportation performance has been through the roof lately, a finding that should lead the Chamber to question some of its assumptions. Source: U.S. Chamber TPI 2011 Update

The Chamber of Commerce released its annual Transportation Performance Index (TPI) last week [PDF], and you can tell it’s due for a total overhaul, because according to the Index, recession-battered 2009 was a banner year for transportation performance.

Using 2009 data, the Chamber, a powerful lobbying group that represents millions of American businesses, determined that the performance of the nation’s transportation infrastructure is improving. However, even the Chamber dismisses the significance of its own results, saying the “improvement” is illusory — due to the decline in driving, and thus congestion, during the recession. But there’s another good reason to dismiss the results: The Chamber is measuring the wrong things.

The Chamber uses the TPI “to track the performance of transportation infrastructure over time… and demonstrate the connection between infrastructure performance, rather than spending, and the economy.” It claims to be the first organization to ever measure the correlation between the quality of transportation systems and economic growth.

But the Chamber’s metrics produce some truly baffling results. During the economic torpor of 2009, the index experienced its greatest improvement in a single year since 1990. Despite the nonsensical figures, the Chamber uses the report release as an opportunity to call for renewed infrastructure investment.

“By all accounts, the nation’s transportation networks continue to languish.” said Janet Kavinoky, head lobbyist for the Chamber’s infrastructure program. “The improvement of the TPI is not sustainable and does not represent a long-term trend… It is due to the economic downturn, rather than strategic policy and regulatory reforms or new investment.”

That’s all true, but that’s not the only reason to question the results of the TPI.

Of the 21 indicators the Chamber uses in its complex formulas, none deal with emissions. Of all of the ways the Chamber chooses to evaluate the U.S. transportation system, none investigates the effect on air and water quality. They certainly don’t take public health into account, ignoring the effect of our transportation choices on our waistlines or our lungs. In fact, the Chamber completely glosses over non-motorized transportation. Pedestrian and bicycle infrastructure doesn’t count as one of the “fixed facilities” the Chamber examines.

Here’s all you need to know to be convinced that the Chamber’s measurements of transportation performance don’t add up: Though it didn’t name the top states for transportation performance this year (that listing only comes out every other year), these were the top winners last year:

Source: U.S. Chamber of Commerce TPI 2010

Maybe that’s what you get when you evaluate performance on congestion based on “route-miles per 10,000 population” — the higher the better. That’s right. The Chamber judges congestion using a simple formula: asphalt divided by people.

The Dakotas don’t have a congestion problem because they have about 10 residents per square mile. If you want to see how a state deals with congestion, check out New Jersey (1,196 inhabitants per square mile). Trying to solve their congestion problem by building more “route-miles per 10,000 population” would be an exercise in futility.

Notably, the Chamber uses the Texas Transportation Institute’s Urban Mobility Report as its gold standard for measuring congestion, saying that methodological revisions in the TTI are a “game changer.” Report authors like that the TTI now measures off-peak travel times and includes San Juan, among other changes.

But those changes don’t address the major defects with the Urban Mobility Report. Real, significant changes would have included a move away from highway traffic speeds as the main measure of urban mobility. CEOs for Cities has produced a detailed review of the report [PDF] that should give the Chamber pause when using it as a primary data source. Among their findings: The UMR rewards longer commute times as long as average driving speeds stay high, and it fails to recognize regions that have actually succeeded in making commutes shorter.

The Chamber’s performance index does take into consideration the availability of transit and rail, as well as safety indicators on all modes. But even the measurements of rail and transit availability only measure route-miles and capacity — not frequency, reliability, ridership, or whether the route miles go to the right places, adequately connecting people with jobs and destinations.

So what are we left with? A transportation ranking that tells us that the wide-open states of the American West have wide-open highways, and that’s good for business. And as soon as those highways fill up with enough vehicles to justify their existence, better build more.

Clearly, as a representative of business interests, the Chamber believes it is looking out for the best thing for economic growth. But the assumptions it’s using are out-of-date. Building a transportation system that produces economic growth in the 21st century does not entail creating the conditions for vehicle miles traveled to rise continually. A recent report from the Center for Clean Air Policy documented how GDP is increasingly disconnected from VMT. Even the Chamber has recognized this trend, stating that “the importance of travel as a component of the U.S. economy has been declining since the early 1990s.”

For next year’s Transportation Performance Index, instead of more metrics praising empty highways, how about a smart growth indicator?

Here’s another jaw-dropping facet of the program, as reported in the Times:

[City engineers] also plan to offer this data to software developers so that drivers and passengers can gain access to this detailed information on their iPads or iPhones.

Distracted driving is a known killer, an epidemic so widespread and pernicious that it even has Albany’s attention. You’ve got to wonder about the logic behind encouraging drivers to pilot their two-ton missiles through streets teeming with pedestrians while not looking where they’re going.

From inside DOT's traffic control center, engineers will now be able to tweak Midtown traffic lights in response to real-time conditions. They'll only be getting information about automobiles, however. Photo: Jill Colvin/DNAinfo.

The Department of Transportation is rolling out a response to Midtown traffic congestion that is as high-tech as it is intellectually outdated. Microwave sensors, video cameras, and E-ZPass readers will gather traffic information in real-time and beam the information to the DOT’s Queens command center, where engineers will instantly adjust the traffic lights as needed in an attempt to fine-tune the workings of the traffic grid.

All that technology, however, will only measure the movement of automobiles through Midtown. Moreover, new turn signals and turning lanes are being added to dozens of intersections in the affected area, between Second and Sixth Avenues and 42nd and 57th Streets. That could mean time and space taken away from other modes and given to automobiles, counter to the city’s transportation goals under PlaNYC.

According to a DOT spokesperson, there is no mechanism currently in place to measure pedestrian volumes in the “Midtown in Motion” area, despite the huge number of people on Midtown sidewalks. Neither is there any transit signal priority, a system that grants a few extra seconds of green light to buses, each of which carries far more people than a few automobiles. Both of those features could theoretically be added to the system at a later date, said the DOT spokesperson.

In the meantime, however, DOT’s highly capable engineers will be told to solve a problem based only on information about motor vehicles. If they wanted to balance the needs of drivers against pedestrians or bus riders in real time, much less prioritize the latter two, they wouldn’t have the tools. Bus riders might benefit incidentally from a bump in overall traffic speeds, but couldn’t be given the extra priority they deserve.

More permanent changes also prioritize traffic capacity over all else. At 53 intersections, turning lanes will be added to the cross-town street, replacing on-street parking, loading zones, and no standing areas. In some cases, what’s being replaced might be important for pedestrian safety, whether by protecting pedestrians on the sidewalk or maintaining visibility at intersections, or needed by local businesses. Notably, the media’s same hyped-up fears about any loss of parking for a bicycle or pedestrian project have not appeared when the space remains dedicated for the automobile.

Dedicated turn signals are also being added to 23 intersections. Light timing is zero-sum; a turn phase has to come from somewhere else. Though DOT’s spokesperson emphasized that pedestrian times would remain within accepted minimum standards, he would not say whether adding turn signals would take away time from pedestrian crossings.

While DOT assiduously requests community board support for bike or pedestrian projects to go forward, the “Midtown in Motion” proposal seemingly went through no public review at all. That’s not because these changes are uniformly uncontroversial. In February of this year, for example, Manhattan Community Board 2 unanimously passed a resolution disapproving of the addition of both turn signals and turning bays on Houston Street, believing that the changes would make conditions more hazardous for pedestrians. Officials who express the utmost concern that all transportation projects earn the support of the local community are silent.

In announcing the new traffic management system, Mayor Bloomberg brought back the transportation rhetoric of the bad old days. “Midtown is the heart of New York City’s economy, traffic is its lifeblood, and we’re about to get that blood flowing even more efficiently using communications technology,” said the mayor, according to a report in DNAinfo.

Of course, a 2006 report by the Partnership for New York City found that only a third of all people traveling to Manhattan below 60th Street came in cars, trucks, or taxis. Midtown is an unparalleled business district not because of road access or traffic management, but thanks to its unparalleled transit capacity and dense, walkable development.

Moreover, the city’s Midtown traffic strategy could very well work against itself. Transportation analyst Charles Komanoff said that by his rough estimate (neither he nor Streetsblog has access to the details of the system), if “Midtown in Motion” adds the equivalent of five percent to the area’s traffic capacity, it would only speed up traffic by an average of 0.75 percent across the Central Business District. That slight speed increase would draw around 1,000 additional drivers into the CBD, slowing things down again. In the end, Komanoff guessed that the plan might only increase CBD daytime speeds from their current average of 9.5 miles per hour to 9.54 mph.

That’s a negligible reward for drivers who clog Midtown streets, and one that comes with no apparent benefit to those who are the true life force of Manhattan’s Central Business District.

Are non-automotive modes squeezing out driving? The jury's still out. Photo: GizMag

In an article titled “We Are Approaching Peak Car Use,” the magazine examines an Australian study [PDF] which found driving rates are falling in a number of cities in Europe, North America and Australia.

Explanations include rising fuel prices, the increasing appeal of urbanism, and another interesting theory: that many urban areas have reached the limit people are willing to drive as part of their daily commute (about one hour).

The study authors conclude that traffic engineers need to change their models and rethink the assumption that traffic will increase annually.

Meanwhile, new data from the Bureau of Transportation Statistics adds to the body of research about the decline in driving — but whether that amounts to “peak car use” is worth further consideration. The report shows a leveling off in vehicle miles traveled, beginning at the end of 2007.

Between 1980 and 2007, urban vehicle miles traveled increased 133 percent, or almost five percent annually. But from 2007 to 2009, urban driving held steady. The change in driving in rural areas was more impressive. Rural vehicle miles traveled declined four percent from 2007 to 2009 after increasing at an average rate of two percent annually between 1980 and 2007.

These numbers don’t point to a cause. But the decline in driving aligns pretty well with the greatest period of economic contraction in a generation. And driving declines have long been linked recessions. Which leaves us wondering, is the decline part of a lasting trend, or does it just reflect a cyclical pattern tied to the economy?

High unemployment is often cited as an explanation for decreases in driving. For example, when traffic fatalities declined nine percent last year, the Baltimore Sun called it the “recession’s silver lining.”

“The silver lining in any recession is a dip – and sometimes a significant dip – in highway deaths,” Russ Rader, spokesman for the Insurance Institute for Highway Safety, told the paper.

And driving isn’t the only mode of transportation to diminish. Many transit agencies have seen a decline in ridership in recent years, even as gas prices climbed. High unemployment rates were widely blamed. LA’s MTA reported a three percent decrease from 2009 to 2011.

“Probably the biggest impact on our ridership right now is the economy,” Marc Littman, a spokesman for Metro, told the LA Times in April. “Until that improves, you probably won’t see an uptick in ridership.”

To the extent that declines in driving are tied to economic turmoil, they might be expected to reverse themselves just as quickly under different circumstances. But it’s difficult to isolate the economic factor from other theories about driving decreases.

An interesting case is that of the Pacific Northwest, where, arguably more than anywhere, transportation officials have taken measures to encourage transit, biking, and walking over driving. Traffic data has shown vehicle miles traveled in this region peaked in the early 2000s, prior to the recession. This is even more significant when you account for population growth in that region over the same period.

On the other hand, in more car-centric metros like St. Louis, transportation data has shown car use continuing to increase. Thanks to its sprawling freeway system, the St. Louis region added 36 hours per year to the average annual commuting time between 1999 and 2009.

Ultimately, only time will tell whether national declines are the result of peak car use or cyclical fluctuations. But some new research points to a promising trend. A report released by the Center for Clean Air Policy this spring indicated that beginning in 1996, US GDP began growing at a faster rate than VMT. That could mean that at the end of this recession — especially given its extremely disruptive nature — a different pattern will emerge, where the economy grows without an accompanying rise in traffic.

Surveys show how few people in Jackson Heights got there by driving. In every neighborhood DOT studied, a substantial majority of people arrived by means other than driving.

NYCDOT’s annual scorecard, the Sustainable Streets Index, adds more information about how New Yorkers get around every year. In addition to regular statistical snapshots of the city’s transportation system, like transit ridership or traffic speeds culled from GPS devices in taxis, this year’s version adds neighborhood travel profiles. Compiled from interviews in eight neighborhoods, these profiles to show just how little New Yorkers rely on cars to get around.

The recent news is not good, however. In 2009, the decade-long trend toward greater transit use reversed slightly, according to the report. Motor vehicle traffic increased by 0.3 percent while transit ridership fell 2.5 percent. DOT attributed the change to the effects of the recession, increased transit fares, and lower gas prices.

The number of transit riders declined in 2009, while traffic rose slightly. Preliminary numbers show subway ridership rebounded in 2010 while bus ridership continued to fall.

Preliminary 2010 numbers show what appear to be the joint effect of the uneven economic recovery and last year’s devastating fare hikes and service cuts. Subway ridership bounced back by one or two percent through October, but bus ridership continued to fall.

While the report is almost entirely a data-driven look backward, with regards to transit ridership it offers a dark warning about future trends:

The big if, however, lies in the area of overall bus and subway service. Given continued State budget shortfalls and pressures on the MTA budget, it is unclear whether the recent pattern of MTA service cuts and fare increases can be broken. In addition, the current MTA Capital Program remains only partially funded. Without firmer financing of the city’s transit system, the gains of the past decade are clearly at risk.

A new feature of the Sustainable Streets Index, the neighborhood travel profiles, offers in-depth looks at how people arrived at eight city neighborhoods and why they went there. In Union Square, for example, only four percent arrived by driving, along with another five percent in taxis. In contrast, roughly half of all people walked there and a third took the subway. Another four percent rode the bus and two percent biked.

Given that 70 percent of the people surveyed were there to shop or eat out, it’s safe to say that making parking more abundant isn’t the key to helping businesses in Union Square prosper. Similar data compiled on other commercial strips could help assuage many merchant concerns about re-appropriating parking spaces for busways, bike lanes, or pedestrian improvements.

In neighborhoods across the city, only a small share of people drive to their destinations. In Jackson Heights, only six percent of interview subjects had driven there, while 65 percent walked. At Fordham, only eight percent had driven, while the largest number — 42 percent — had taken the bus.

Even in the two neighborhoods with the largest share of drivers in their profile, a substantial majority got there using another mode. In Astoria, only 22 percent had driven. On Staten Island, 39 percent of people drove to New Dorp, with another one percent using a car service. The remaining three-fifths walked or took transit.

DOT mapped the prevalence of bike commuting across the city according to Census data, which may undercount the number of cyclists.

The report also highlights some truly gaudy bike numbers. Which streets have high cycling mode-share? One place you can’t go wrong is Prince Street, where biking constitutes 37 percent of evening rush hour traffic. On East 10th Street, 32 percent of the evening rush is bike traffic. A bike lane on Rockaway Boulevard increased cycling by 268 percent, though that number was an outlier; it was more common for bike counts to post double digit percent increases after the installation of a new bike lane.

The bulk of the report is dedicated to presenting the results of 11 major projects. Some of them, like the safety-enhancing redesign of Allen and Pike Streets or the congestion-curbing Park Smart program in Park Slope, have already been covered on Streetsblog, but here are some of the other projects:

• On Gerritsen Avenue in Brooklyn, reducing the street from two lanes in each direction to only one cut the total number of crashes by 48 percent (bike lanes were in the original plan, but were replaced by a painted median at the request of the community board). Speeding fell 30 percent among northbound cars without creating congestion.


GPS data from taxis allowed DOT to map average traffic speeds in Manhattan. The brighter the red, the worse the congestion.

• Where the Pulaski Bridge meets Jackson Avenue, there hasn’t been a single injury to a pedestrian or cyclist since changes were made to the intersection 17 months ago. There, a reconfigured intersection clarified vehicle movements, a pedestrian-only signal phase gave those on foot some extra time to make it across the intersection, and a new refuge island shortened crossing distances.
• After eight years of planning and construction, changes to West Houston Street cut the number of crashes involving injuries by 24 percent. Those included pedestrian refuges and neckdowns, but also sizable increases in traffic capacity.
• The changes to Park Circle, at the corner of Prospect Park, managed to decrease travel times for cars on every leg of the circle while simultaneously making it easier to walk around the circle, adding bike lanes, and calming traffic exiting the circle.
• As part of the Pelham Gardens Safe Streets for Seniors program, Allerton Avenue was narrowed from two lanes to one in each direction, with the extra space being used for a wide center median and a bike lane. There, the results have been positive, but more modest. The crash rates for pedestrians and cyclists are down, but not by a statistically significant margin. Similarly, speeding decreased, but only by four to seven percent; a majority of the cars on the road still are driving more than 30 miles per hour.
• Belying the media-generated perception of DOT as rabidly anti-car, some of the featured projects were entirely to improve automobile movement. Where the Belt Parkway and Bay Parkway meet, for example, an additional lane increased traffic capacity on Bay Parkway by 34 percent.

Graph: Office of the mayor

A new study commissioned by the city finds that air quality in Times Square has notably improved since the 2009 installation of pedestrian plazas on Broadway.

Street-level readings taken by the New York City Community Air Survey, a city-wide air quality monitoring program created as part of PlaNYC, show that “concentrations of traffic-related pollutants were substantially lower than measurements from the year before and were less than in other midtown locations.” From a media statement announcing the findings:

The report confirms that major sources of air pollution generated in New York City are vehicle traffic and buildings burning high-sulfur heating oils. Additionally, in Times Square, concentrations of nitrogen oxide (NO) and nitrogen dioxide (NO2), two pollutants closely associated with traffic, were among the highest in the city. After the conversion to a pedestrian plaza, NO pollution levels in Times Square went down by 63 percent, while NO2 levels went down by 41 percent.

“The new Times Square is a showcase for New York’s vitality and energy, rather than for congestion and pollution,” said NYCDOT Commissioner Sadik-Khan. “The changes here have been big wins for safety, mobility and business. Now we can see that they have delivered great environmental gains as well.”

The city says that some 250,000 pedestrians enter Times Square every day.

Data from the survey were released ahead of the next edition of PlaNYC and will be used to “inform” unspecified new air quality initiatives. The PlaNYC reboot is set for April 21.

Among the fans of the new Times Square are former President Bill Clinton, who joined Mayor Bloomberg today in announcing a merger of their climate groups, the Clinton Global Initiative and C40. Regaling reporters with tales of the Times Square of old, writes City Room:

Mr. Clinton concluded by recalling that when he was a college student, he was agile — and reckless — enough to dodge the cars zipping through Times Square.

Today, thanks to the pedestrian mall, he said, there is no need. “Now you can be my age and walk in Times Square and not get run down. That is pretty cool, too.”

The only thing more congested than Canal Street might be Canal Street's sidewalks. Photo: Bertrand Duperrin via Flickr

Canal Street, to put it mildly, is due for a makeover. The street is clogged with traffic from the Holland Tunnel and the un-tolled Manhattan Bridge. Pedestrians jostle for space on the packed sidewalks, and they’re especially at risk of getting hit by a car, according to the city’s Pedestrian Safety Study.

Fortunately, the funds are in place for an eventual reconstruction and re-imagination of the street, thanks to federal World Trade Center emergency relief aid. To help determine how to design Canal Street, which must strike a balance between serving the local community and the regional transportation system, NYMTC, the region’s metropolitan planning organization, has been engaged in a nearly decade-long process of studying the area and drawing up recommendations for the corridor.

In a report released last Thursday [PDF], NYMTC recommends making Canal Street friendlier for pedestrians by adding significant amounts of sidewalk space. But larger changes, in particular the creation of a carpool lane in the Holland Tunnel, weren’t included. According to the NYMTC report, NYCDOT has agreed to use the recommendations to inform its plans, though a DOT spokesperson said only that the agency was reviewing the findings.

The Canal Area Transportation Study process began in 2002, and the first phase ended with some relatively small improvements to the area, like high-visibility crosswalks, new signage, and temporary improvements near Allen Street. Since 2005, the second, larger-scale phase of the study has been underway, bringing together all the regional transportation agencies as well as others with a stake in the project.

The NYMTC team studied a wide array of congestion-busting ideas for the corridor. Some, like two-way tolling on the Verrazano Bridge or congestion pricing, were dismissed because they required legislative approvals well outside the project’s scope. Transit expansions, like bringing the PATH train north from the World Trade Center or building light rail on Canal, were rejected as too costly. Some ideas were nixed because they lacked community support or because they conflicted with New York City’s Street Design Manual. Other ambitious proposals, like keeping traffic off side streets including Pell, Doyers, Mosco, and Mulberry, were referred to the appropriate agency for further study.

What’s left still has a lot to like.

In addition to a few recommendations that have already been implemented, like a HOV lane on the Manhattan Bridge and a median on Bowery, the plan calls for significant new pedestrian amenities. Those include leading pedestrian intervals at intersections and a redesign for the intersection of Bowery and Canal, at the foot of the Manhattan Bridge. Curb extensions would be built on Canal at Varick Street, between Elizabeth and Mulberry and between Baxter and Lafayette, replacing traffic lanes.

A separate memo on parking policy [PDF] also puts forward some powerful suggestions for making the most of scarce curb access and reducing parking-induced driving. That document recommends a further crackdown on parking placards, which in Lower Manhattan would significantly cut traffic. It also suggests that Park Smart might be successful in the area and puts forward the goal of keeping ten percent of spaces open at all times, which Donald Shoup would approve of. Though the report does raise the idea of building more parking on the area’s periphery, it notes that this hasn’t been particularly successful in other downtowns.

But NYMTC recommends against one significant change. Putting a HOV3 lane through the Holland Tunnel, the NYMTC model found, would shift cars with one or two passengers from the Holland Tunnel to the Lincoln Tunnel, George Washington Bridge, and Staten Island crossings. A NYMTC spokesperson added that those new trips, since less direct, would likely add extra vehicle miles traveled overall, and that a HOV lane already exists for the approach to the tunnel on the Jersey City side. While the tunnel itself would have less traffic with a HOV lane, NYMTC projected, the Manhattan streets it empties into would just fill up again with other traffic from the over-congested streets nearby.

NYMTC also looked into turning Canal Street one-way headed east, pairing it with a westbound Grand Street. While that option would have allowed for even wider sidewalks on Canal, wrote NYMTC, “the wider Canal Street sidewalks in the one-way alternative would be offset by the negative traffic impact of the one-way pair on both Grand Street and Spring Street.” In other words, the cars won out over the pedestrians on that one.

The study also includes a wealth of data for those interested in the area’s travel patterns. Congestion on Canal Street is worst on Sundays, for example, because non-work trips mean that there are more turns onto side streets, more cruising for parking, and more passenger drop-offs. The sidewalks are the most overcrowded between Broadway and Centre Streets. And during the weekday rush, there are roughly equal amounts of vehicles crossing Manhattan, beginning or ending their trip in Manhattan, and traveling within the Canal Street area.

DOT Commissioner Janette Sadik-Khan and City Council transportation chair Jimmy Vacca measure speeds on Atlantic Avenue with students from PS 261. Photo: Ben Fried

Students at Brooklyn’s PS 261 have clocked motorists traveling on Atlantic Avenue at an average midday speed of 38 mph — and as high as 50 mph. While the city’s 30 mph speed limit is a mystery to most New Yorkers, the students knew they were watching people break the law and put others in danger.

As part of a new program through NYC DOT’s Office of Education and Outreach, these fourth graders recently picked up some lessons about traffic safety (and math and physics), like the fact that stopping distances increase exponentially with vehicle speeds. Their teacher, Colleen Greto, said a jaw-dropping moment came when kids chalked out 160 feet — the stopping distance for cars traveling at 40 mph — on the ground of their schoolyard.

Just knowing the speed limit makes these kids experts on driving safety compared to most people who live in this city. “You guys know more than seven out of ten New Yorkers,” Transportation Commissioner Janette Sadik-Khan told the class at a press event yesterday announcing the program.

The new curriculum is a departure from longstanding street safety education tactics, which portray car traffic as an implacable force of nature. The underlying premise is that there’s more to safety education than looking both ways before you cross the street.

“We’re asking kids not just to learn how to be better pedestrians, but how to ask drivers to be better drivers,” said DOT education and outreach assistant commissioner Kim Wiley-Schwartz (formerly of Livable Streets Education, a project of OpenPlans, Streetsblog’s parent organization). The city is looking to bring the curriculum to other schools, especially ones located in areas with high rates of crashes and injuries.

With the city embarking on a campaign to raise awareness of the speed limit and why it matters, teaching kids about the risks of speeding could help get the message out and change attitudes. “Boys and girls like you can be eyes and ears for adults,” said City Council transportation chair Jimmy Vacca at yesterday’s presser. “You can let adults know that they go too fast too often.”

Fourth grader Kiara Aramore said she already told her mother about the 30 mph speed limit. “If you ever get into a car, it’s important for safety,” she said. While her mom doesn’t own a car, Kiara said that “if she gets into a car she should tell the person who’s driving to go the speed limit.”

You may have wondered, while watching a Streetfilm or reading a post on Streetsblog, where we got the term “livable streets.”

The answer can be found in the work of Donald Appleyard, a scholar who studied the neighborhood environment and the ways planning and design can make life better for city residents. In 1981, Appleyard published “Livable Streets” based on his research into how people experience streets with different traffic volumes.

Today we’re revisiting Appleyard’s work in the second installment of our series, “Fixing the Great Mistake.” This video explores three studies in “Livable Streets” that measured, for the first time, the effect of traffic on our social interactions and how we perceive our own homes and neighborhoods.

An analysis by CEOs For Cities shows that contrary to previous reports, the longest commutes are in sprawling Southeastern cities. View a larger version of this infographic. Image: CEOs for Cities

Imagine two drivers leaving downtown to head home. Each of them sits in traffic for the first ten miles of the commute but at that point, their paths diverge. The first one has reached home. The second has another twenty miles to drive, though luckily for her, the roads are clear and congestion doesn’t slow her down. Who’s got a better commute?

Shockingly, the standard method for measuring traffic congestion implies that the second driver has it better. The Texas Transportation Institute’s Urban Mobility Report (UMR) only studies how congestion slows down drivers from hypothetical maximum speeds, completely ignoring how long it takes to actually get where you’re going. The result is an incessant call for more highway lanes from newspapers across the country.

An important new report from CEOs for Cities, though, has laid out major problems with the UMR. It shows how commuters in compact regions, whose daily trips look hellish based on the UMR, actually spend far less time in the car than residents of sprawling metro areas.

The misleading metrics in the UMR are a convenient bludgeon for the highway lobby. According to report author Joe Cortright, the UMR serves as “a drumbeat saying we need to spend a lot more on expanding capacity. It gets used in political speeches, it’s used in lobbying.”

The key flaw is a measurement called the Travel Time Index. That’s the ratio of average travel times at peak hours to the average time if roads were freely flowing. In other words, the TTI measures how fast a given trip goes; it doesn’t measure whether that trip is long or short to begin with.

Relying on the TTI suggests that more sprawl and more highways solve congestion, when in fact it just makes commutes longer. Instead, suggests CEOs for Cities, more compact development is often the more effective — and more affordable — solution.

Take the Chicago and Charlotte metro areas. Chicagoland has the second worst TTI in the country, after Los Angeles. Charlotte is about average. But in fact, Chicago-area drivers spend more than 15 minutes less traveling each day, because the average trip is 5.5 miles shorter than in Charlotte. Charlotte only looks better because on average, its drivers travel closer to the hypothetical free-flowing speed.

For Cortright, perhaps the biggest problem with the UMR is that it suggests traffic congestion is always getting worse. “One insight from our reanalysis is that in some places it’s getting better,” he said, “and it’s getting better because people are changing the pattern of the trips they’re taking.” In Portland, Oregon, for example, the TTI got much worse between 1982 and 2007. But in fact, by reducing average travel distances from 19.6 miles to 16.0 miles over that period, Portland shaved 11 minutes of peak travel off its average commute.

The CEOs for Cities report concludes that the UMR not only measures the wrong things, it also measures things the wrong way. For example, it doesn’t use observed speeds to calculate how much congestion slows down traffic during peak hours, but relies on a mechanistic model based on the total number of cars moving in a full 24-hour period. When showing the amount of gas that congestion wastes, it relies on an outdated study that incorrectly assumes faster speeds are always more fuel-efficient.

The officer who drove the wrong way down Jay Street and injured a cyclist near the foot of the Manhattan Bridge last month will face three misdemeanor counts filed by the Brooklyn District Attorney.

Louis Ramos, an officer with the 84th Precinct, was behind the wheel of a squad car with his partner, Paris Anderson, when they struck 61-year-old Yu Tong Chan at the intersection of Jay and Sands Street, which sees some of the heaviest bike traffic in the city. Chan was knocked off his bike and sustained a broken nose. He later reported the incident, but the officers did not.

Surveillance footage posted by 1010 WINS shows the officers hit Chan, then exit their vehicle for about four minutes before driving away. According to the Daily News, during this time the officers "helped the victim to the sidewalk and gave him tissues to clean the cuts and abrasions on his face, arms and legs." Both explained their failure to report the collision by claiming that they thought Chan had fallen off his bike after being startled by the lights and sirens of the patrol car.

The Brooklyn DA has charged Ramos with reckless driving, reckless assault, and leaving the scene of an accident. The arraignment will be held tomorrow.

The Brooklyn and Manhattan bridges, covered in smog generated in large part by tailpipe emissions. Image: Wikimedia

New Yorkers shouldn't have to live in homes where garbage, mold and rats cause asthma, and they shouldn't have to play in parks where PCBs are 110 times the level considered safe. For the city to have a truly clean and healthy environment, elected leaders needs to do more about pollution from cars.

According to the Environmental Defense Fund, vehicle emissions contribute more than 80 percent of the total cancer risk from air pollution. The health effects of tailpipe emissions are highest within 500 feet of congested major roadways. The homes of two million New Yorkers are inside that high-risk area, according to another EDF report. In Brooklyn, 35 percent of playgrounds are in the danger zone. EDF also estimates that Queens County has the tenth worst diesel pollution in the country.

More than a million New Yorkers have been diagnosed with asthma, and the harm from automotive pollution is felt most acutely in disadvantaged communities. "Communities living close to highways, high traffic volume and congestion tend to have higher asthma rates and hospitalizations," said Soledad Gaztambide, transportation justice coordinator for the United Puerto Rican Organization of Sunset Park. "These communities are mostly low-income communities and communities of color."

Gaztambide identified the upcoming cuts to MTA service as a major step backwards in the fight to keep New York's environment healthy. "The city and state need to prioritize the creation of new revenue sources for the MTA to divert further service cuts and fare increases," she said. "Funding support from the city and state has remained the same while MTA operating costs continue to grow."

The City Council has the budget powers to give more money to transit, the land use authority to stop filling new development with off-street parking, and the bully pulpit to build support for pedestrian and bike infrastructure in New York's political culture, just to name a few options at their disposal. If council members want to improve the environment and public health, cars have to be a target.

In 2008, transit ridership continued to increase while auto traffic declined. Image: NYCDOT.

Last year's index showed how transit had absorbed all the growth in travel as the NYC economy expanded from 2003 to 2007, with driving remaining essentially flat. The new index reveals how that pattern continued in 2008, with the largest decline in traffic in at least 15 years. Not all the numbers for 2009 are in yet, but it looks like the recession caused declines in both transit ridership and driving, not a shift toward automobiles. You've got to wonder whether transit ridership will hold its own in 2010, after the package of sweeping MTA service cuts takes effect.

Most of this year's report is devoted to case studies of street redesigns and bus improvements across the city. Lately we've heard DOT cite safety stats from projects like the new Broadway and the Ninth Avenue bike lane when making the case for pedestrian and bicycle improvements, like those slated for First and Second Avenues. The new index catalogs several other interventions, often showing that re-orienting streets to serve sustainable modes hasn't caused dreaded traffic tie-ups:

For the real transportation geeks out there, the coolest addition to this year's index has to be the wealth of data from GPS systems installed in New York's taxis. Because they track every aspect of every trip that every taxi takes, these GPS units yield information about traffic street-by-street and minute-by-minute. The Sustainable Streets Index provides a few headline numbers -- traffic speeds in Midtown increased by 18 percent between fall 2007 and fall 2009, for example -- but DOT has already put more fine-grained data to use. The taxi GPS data is what they used to demonstrate that pedestrianizing Broadway didn't cause carmaggeddon.

Fewer cars means more walking and healthier kids. Image: jeweledlion via Flickr.

Could reducing traffic near children's homes help America combat its obesity epidemic? A new study conducted by UC Berkeley professor Michael Jerrett strongly suggests the answer is yes.

Obesity rates are steadily increasing -- more than one-fifth of New Yorkers are now obese, and even that figure is well below the national average. With obesity strongly linked to dangerous diseases like diabetes and asthma, a great deal of research has gone into uncovering the factors at work.

The quality of the built environment matters tremendously. Everything from mixed-use development to street connectivity to park access has been shown to affect physical activity, Jerrett notes, thus affecting obesity rates.

The new research, published in the journal Preventive Medicine, makes a crucial addition to what we know already. Jerrett shows that not only does the built environment matter, but traffic volumes matter too. His team's long-term study tracked children from across Southern California, starting from ages 9-10 and continuing through high school. Controlling for a wide variety of factors, they compared the children's body mass indexes (BMI) to the density of traffic near their homes.

Children living within 150 meters of high-traffic areas were found to have, on average, BMIs five percent higher than those living near low-traffic areas. Only the immediate surroundings seem to matter: Traffic levels within 300 or 500 meters didn't affect BMI.

The researchers put forward two explanations for why high traffic contributes to obesity. The first is that real or perceived danger from cars reduces walking and biking. The other is that too much traffic contributes to high asthma rates, which make physical activity more difficult and less frequent.

James Sallis, director of the Active Living Research Program at the Robert Wood Johnson Foundation, which commissioned the study, says Jerrett's research stands out because it tracked a large sample of kids for a long period of time, giving it strong scientific value. "This actually points to some solutions," he added, noting that not every study commissioned by the program has such clear implications for policy.

Just last week, New York City released its Active Design Guidelines, bringing together the city's transportation and city planning departments with the health department. Jerrett's report suggests that policies that help reduce traffic -- like congestion pricing, performance parking, and off-street parking reform -- should be a necessary component of the effort to fight obesity and improve New Yorkers' health.

A prime target of the early environmental movement was car tailpipes. And for good reason. Put a human in a garage with a running auto in the old days, and he or she would pass out within minutes and be dead in an hour. Run a few million vehicles daily in New York or Los Angeles, and the toxic air would kill thousands each year and sicken many more.

But as the saying goes, that was then, this is now. Cars now on the road are 30 to 50 times less polluting than in 1970. True, there are more cars being driven more miles, but even with a tripling of VMT (vehicle miles traveled), U.S. passenger vehicles today are probably putting out only a tenth as much air pollution as they did on the first Earth Day. Even trucks and buses are getting cleaned up. Thanks to advocates like NRDC attorney (and local transportation advocate) Rich Kassel, diesel fuels and engines are in a decade-long transition from dirty to clean. (Stood behind a soot-belching NYC Transit bus lately? Me neither.)

Old notions die hard, however. Witness the asthma mantra before and during the unsuccessful 2007-08 campaign for Mayor Bloomberg's congestion pricing plan. And just last week, the New York Times picked up the same cudgel in a New Year’s Day editorial:

The latest report on air quality from the city’s health department is especially alarming: it showed unhealthy levels of pollution in high-population areas throughout the city. Mr. Bloomberg should revive his fight in Albany for some form of congestion pricing.

A classic non sequitur: Yes, pollution is still at unhealthy levels; yes, congestion pricing is needed; but the link from the first fact to the second is tenuous.

To see why, please pay a visit to the Balanced Transportation Analyzer. I’ve set the BTA with “Kheel-Komanoff” inputs: a variable $3-$6-$9 toll to drive into the Manhattan Central Business District (less on weekends and holidays), a 33 percent taxi fare surcharge, and revenues dedicated to make subways and buses cheaper and free, respectively. But my point holds with almost any cordon-based congestion pricing plan:

Direct environmental benefits from congestion pricing -- fewer crashes, less traffic noise, reduced carbon emissions, and cleaner air -- are worth only one-tenth as much, combined, as the time that users of autos, trucks and buses will save getting around. The air pollution benefit alone, computed as the monetary value of fewer illnesses and deaths, is less than $100 million, even counting the reduction in stop-and-go driving inside the CBD, where traffic speeds during the morning and evening peaks are predicted to increase 20-25 percent. In contrast, the projected time savings are worth $2.5 billion, or roughly 25 times as much as the improvement in air quality.

How can this be? The 25-fold difference between time benefits and air benefits isn’t from cooking the numbers. I’ve programmed the BTA with conservative estimates of the “value of time” and liberal estimates of the health value of curbing soot and ozone-forming gaseous pollutants. (I doubled the dollar-per-ton values that the hawkish California Air Resources Board uses to screen antipollution measures.)

Rather, there are three reasons that in almost any congestion pricing plan, whether Kheel-Komanoff or Bloomberg or Ravitch, the value of the time savings will dwarf the air quality benefits:

1. On a regional basis, congestion pricing eliminates only a small percentage of VMT. Ditto, tailpipe emissions.
2. Emissions from present-day cars (and, increasingly, trucks and buses) are low and trending lower. Thus, the vaunted improvements in traffic flow won't eliminate much car exhaust, because there isn’t much to begin with.
3. Time savings from tolling gridlocked roads rise geometrically with congestion. A given percentage increase in speed saves six times as many minutes when the base speed is 5 mph as when it's 30 mph. Considering that slow speeds also imply high volumes, congestion pricing is practically ordained to generate big time savings -- particularly if the tolls are varied by time of day and day of week.

The lesson for congestion pricing advocates is clear: give the "green" angle a rest. We're not in 1970 anymore. (If per-mile emission rates hadn't changed since Earth Day, the air quality benefits would be some 40 times greater, equaling or even surpassing the time savings.) Clean air no longer provides a powerful rationale for congestion pricing.

From a cost-benefit standpoint, the overwhelming reason to adopt congestion pricing in New York City -- in addition to providing a vital new revenue stream for public transit, of course -- is to enable people stuck in traffic to save time.

Curing aggravation, not asthma, should be motivation enough for congestion pricing.