Daily gridlock traffic might seem like it’s draining the life out of you. For some, in cities throughout the world, it actually is. The main culprit: not the traffic itself, but the air pollution it creates. Air pollution does indeed cut lives short, as several studies have shown—including one by my colleagues and I that found people living in India are losing 3 years off their lives due to bad air pollution. In some cities, as much as 75% of that air pollution comes from vehicles.

Global Annual Average Particulate Pollution (PM2.5)
Satellite-based data shows the levels of PM2.5 pollution globally, with red being the highest levels.

Strong, lasting and comprehensive transportation policies make the difference between traffic being a daily nuisance or a quiet killer. While the transportation sector remains a heavy segment of U.S. emissions, the Clean Air Act—in terms of vehicles, through fuel economy standards—is helping to extend lifespans by cutting pollution through broad polices.  But from Paris to my home in New Delhi, governments are trying to solve their pollution woes with band-aide approaches. They are not recognizing that lasting changes require lasting policies.

To take a concrete example, in response to Delhi’s worsening traffic, the government decided to introduce the ‘Odd-Even’ scheme. Twice over the last several months the government banned cars from driving on city streets on alternate days of the week depending on whether their license plate ended in an even or odd number.

Did it work? My colleagues and I compared pollution trends in Delhi before and during the first odd-even pilot in January to trends outside of Delhi where weather and other factors would have been similar. We found that the first experiment reduced pollution by 10-13%. But, we questioned the durability of the program. Our skepticism proved correct. In April, when we analyzed data from the second round of the pilot, we found no significant impact in congestion or pollution.

Reduction in Particulate Pollution (PM2.5) Concentrations in Delhi during Odd-Even Pilots
In January, during the daytime period when the Odd-Even pilot was in place, there was a statistically significant reduction in PM2.5. However, the pilot did not see the same success during the April period.

New Delhi isn’t the only city attracted by such a scheme. A similar program is running in Mexico City until the end of this month, instituted in April as an emergency effort to alleviate a sudden spike in pollution. The government instituted the ban even though they knew from experience that the program wouldn’t be a lasting solution. A prior, longer-run program showed that pollution reductions vanished as commuters bought cheaper, second-hand and often higher-polluting cars.

There are other examples of such policies going wrong. For instance, California’s Cash for Clunkers scheme, meant to get people to turn in old cars, ended up helping a lot of people who were planning to upgrade anyway—eating away many of the benefits.

Instead, my colleagues and I have argued repeatedly that cities like Delhi should consider instituting comprehensive transportation policies such as a congestion tax, where at certain places and times drivers are charged for using the roads. A congestion tax would be more likely to ensure sustained progress in lowering pollution, partly because it would both increase the need for and raise the revenue to invest in high-quality, high-capacity public transport. Investing in such public transport as a subway system has been shown in itself to reduce congestion, and therefore, air pollution.

Delhi would hardly be the first to introduce such a change. London, Stockholm and Singapore all have congestion taxes. And, many other cities are now considering jumping on the bandwagon. Beijing, where the number of cars on the road rose 17% over the last five years, has completed draft plans to impose a congestion charge. Mexico City is also considering it, while London may raise the fee in some areas.

Since it’s been around for a while, there’s been time to gather the evidence to prove that such a fee does work. One study, for instance, of the program in Gothenburg, Sweden found that it reduced traffic by 12% during the charging hours, with many choosing public transit instead. The congestion charge also grossed €72 million in the first year. The neighboring Stockholm, a much larger city than Gothenburg, saw similar reductions in traffic and increases in public transit. The program there generated €76 million in revenue during 2013. At the same time, pollution levels in Stockholm, like in London and Singapore, have decreased since the fee system went into place.

While the evidence is in, government decisions don’t rest solely on the solutions that make the most sense. Political and public will, and the capacity of governments to implement the system successfully, are all important factors. A panel commissioned by the Delhi government came out with a report this month that provides several long-term solutions to pollution from traffic in the city. One of those solutions was a congestion tax. Yet, Delhi has not made any real steps towards introducing this idea (or others of its type). It’s not alone. New York City, has been trying to pass some form of a congestion tax since the 1970’s.

But there is a big difference between Delhi and New York. When looking at the worst polluted cities in the world, New York ranks toward the bottom of the list. Delhi comes in at number eleven. Another city high on that list is Beijing, where the public drive to lower pollution is great enough that 53% of those polled support the congestion fee that’s been proposed. Delhi’s government and citizens are feeling a similar urgency to take action. So, support there might soon exist.

If Delhi were to be the next city to institute such a sweeping change, the change would not just improve pollution and carry Delhi into the future with cleaner public transit. It would also allow Delhi to be a model for other cities to follow by putting Delhi on a list of progressive cities taking smart actions to combat pollution. The longer this list grows, the easier we’ll all be able to breathe.

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