Parisians who take public transit were met with a treat on Wednesday, as the city sought to counter excessive air pollution by making public transportation free.

Wednesday marks the second day of the effort, after skyrocketing pollution levels blanketed the city in the worst smog it has seen in ten years. The city’s free public transportation day is also accompanied by a driving ban for cars with even-numbered license plates.

Other cities around the world have employed similar methods to reduce smog, although some argue that such measures represent only temporary fixes.

“Why put a band-aid on this systemic problem?” asks Tufts University urban and environmental planning professor Julian Agyeman. “What cities need to be doing is integrated transportation planning.”

Paris’s even/odd license plate number scheme is a time-honored strategy for temporarily reducing pollution. Paris has employed it before, as have a number of Asian cities that also struggle with heavy smog.

Even in America, license plate bans have been used to regulate resources and keep cars off the road. Many Americans may remember the months in the late 1970s when President Jimmy Carter allowed state governors to regulate gasoline purchasing in their states due to the energy crisis that occurred in the wake of the Iranian Revolution. The governors of New York and New Jersey were among those who chose to institute an odd/even gasoline purchase ban.

In Mexico City, programs such as “Hoy no Circula,” which keeps motorists off the streets one day each week, and emissions testing also help the city combat its smog problem, while public awareness programs from Japan to the United Kingdom are educating motorists about how they can do their part to help reduce pollution.

Nicole Orttung reported for The Christian Science Monitor on worldwide anti-pollution measures in July of this year. She wrote:

The London campaign hopes to make drivers aware that, when stopping for even 10 seconds, it’s best to turn off your engine, because 10 seconds of idling uses more energy than restarting the engine. The vehicle’s engine warms twice as quickly when it is driven, so drivers should also drive the vehicle slowly at first to warm up the engine rather than idling in a parking spot. It’s often difficult for local governments to get the word out about air quality advisories, and even harder to compel action. A 2008 study of residents in Portland, Ore., and Houston revealed that one-third of residents surveyed were aware of air quality advisories, but only about 10 to 15 percent of citizens changed their behavior.

Nevertheless, Dr. Agyeman says that temporary measures cannot combat the real problem of too many cars on the road.

Improving public transit can make decongestion more feasible, he says. Thus far, Paris’ public transit systems have struggled under the pressures of increased ridership. The RER B commuter line, for example, faced significant delays on Wednesday morning.

Quality of service plays a big role in whether even the most environmentally conscious commuters use public transit, says Madeline Brozen of the UCLA Lewis Center and the Institute of Transportation Studies in a phone interview with The Christian Science Monitor.

And in a city the size of Paris, making public transportation free produces challenges. Ms. Brozen tells the Monitor that while free public transportation is a strategy that has worked on a smaller scale – UCLA’s free transportation program increased ridership by 50 percent and took cars off the road – it is incredibly hard to achieve in a city of more than two million people.

Another strategy is to charge congestion fees – a financial penalty that car owners must pay in order to bring their vehicles into high traffic areas at peak times. London and Singapore both employ this tactic.

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Ironically, despite the city’s short-term strategies for dealing with a long-term pollution problem, Paris Mayor Anne Hidalgo is now the Chair of C40 cities, a network of world cities devoted to fighting climate change.

“C40 member cities are determining the course of our planet’s future,” said Mayor Hidalgo in a statement after her election to C40 Chair. “Thanks to the leadership of Mayor Paes, C40 is a unique forum where cities can collaborate, share knowledge and drive measurable and sustainable action on climate change. I am honoured to be elected as Chair, and look forward to working with the mayors of the world’s great cities to create a sustainable and equitable future for all of our citizens.”