For the last two weeks Mexico City has been immersed in its worst environmental crisis in the last 14 years. The air was so polluted that President Enrique Peña Nieto had to intervene and ordered emergency measures in an attempt to protect the health of more than 20 million people.

In response, the city's government is taking one million old and new cars alike off the road each day of the week for the next three months in an effort to reduce the alarming pollution levels. This expansion of the city's Hoy No Circula program — which stipulates that certain vehicles must stay off the road one day a week — has been met with skepticism from a beleaguered public.

The driving restrictions will be valid for all motorists in Mexico City and in 18 municipalities in the neighboring State of Mexico.

And even though this is not the first time such "emergency measures" have been put in place, many citizens are angry, and scientists doubt the program could help bring about a permanent solution.

On Friday, a poll by the newspaper Reforma found that 63 percent of people living in Mexico City disapproved of the government's approach, and 53 percent think the banning of more vehicles would make no difference on the pollution problem.

The prohibition has highlighted the lack of sufficient public transportation in Mexico's capital. The already overcrowded and inefficient metro system, the city's busiest public transport, experienced a 30 percent increase in passengers in just the last week.

Critics also said this decision could be seen as government overreach.

The toughening up of Hoy No Circula — Spanish for "Today Don't Circulate" — won't be permanent. The city's environmental commission said it will last from April 5 to June 30, around when seasonal rainfall begins. Once the test-period for this measure comes to an end, the commission could decide on making it permanent or returning to the old restrictions, which focus on vehicles eight years or older.

Previously, after undergoing emissions testing to determine the amount of pollution they emitted, cars could circulate freely. But if a car gets negative scores, it could be ordered off the road for one or two days a week.

In the meantime, the Mexican scientific community largely agreed that the banning of cars is just "a temporary solution with a total lack of scientific basis," the Center of Atmospheric Studies of Mexico's national university (UNAM) said in a statement on Thursday.

"What's really behind the problem is the messy urban expansion that affects air quality, ecological reserves, crops, and water resources. In summary, the sustainability and viability of the Mexican megalopolis," the statement said.

Other scientists have doubts that the government's strategy against road traffic has any actual effect on reducing the pollution. Smog in Mexico City is caused by a combination of vehicle emissions, heavy industrial output, and the city's high-altitude bowl-shaped valley.

Doctor Héctor Riveros of the Physics Department at UNAM participated in the environmental commission when the first Hoy No Circula program was implemented in 1992. Since then he predicted that taking cars out of traffic could actually make things worse.

"The Hoy No Circula program has never worked, traffic may have diminished a little, but pollution levels have not changed. For example, supposing we get half a million cars off the streets, we would be sending 800,000 people to the public transport system, which pollutes between four and five times more than private cars," Riveros said, referring to the thousands of microbuses and other polluting vehicles that already choke the city's streets.

According to the scientist, the only time pollution went down slightly was in the early 2000s, after the Mexican state-owned oil company Pemex improved the quality of the fuel it sells, and when the government made it obligatory for all cars to have a catalytic converter — a device which filters the excessive contaminants coming out of the exaust systems of vehicles.

"The only real solution here is to improve the fuel," Riveros said. "If we do that the contaminants in the air would reduce between 30 and 50 percent. But the only real solution is people avoiding having to travel long distances to get to work."

Despite this, Mexico City Mayor Miguel Ángel Mancera said on Tuesday his administration will push to make the measure permanent and asked the federal government for a special budget of at least 30 million dollars to improve the public transportation.

Until now the only vehicles exempt from these measures are those with federal license plates, and vehicles used by civil protection, health services, public security, and schools. Hybrid and electric cars are allowed on the road every day.

Gabriela Gorbea contributed to this report.