TEHRAN – While the low emission zone (LEZ) scheme, mandating vehicle inspection, went into effect in the capital city of Tehran to reduce emissions, only 1.5 percent of the particulate matter (PM) 2.5 is reduced in case of full implementation of the scheme, Mohammad Kazemi, an environmental policy researcher has announced.

LEZ is a defined area where access by certain polluting vehicles is restricted or deterred with the aim of improving the air quality. This may favor vehicles such as hybrid electric vehicles, or zero-emission vehicles such as all-electric vehicles.

To bring LEZ scheme into effect all the vehicles in Tehran are required to get inspection stickers indicating the level of emission they produce which are easy to track down by the traffic cameras thanks to the newly integrated vehicle inspection system.

The first phase of the scheme started in Tehran on September 5, 2016, aiming to mitigate air pollution in the metropolis, which was running from 6 a.m. to 7 p.m. each day except for holidays, while the second phase is set up to run for 24 hours a day, which went into effect since past three months.

The scheme replaced the odd-even number license plate scheme (where depending on the weekday the cars with only odd or even number plate were allowed to drive) in a zone stretching over 80 kilometers of the central Tehran.

Kazemi went on to explain that Tehran's air pollution has been a particular concern over the recent years, due to causing problems for the residents’ health and daily routine, nevertheless, limited studies have been carried out on determining the main pollutants and their sources in order to identify scientific and efficient solutions.

Referring to seven successful solutions and methods practiced in other countries to reduce PM 2.5 emissions, he noted that scraping the clunker vehicles, equipping buses with diesel particulate filters, replacing diesel motorcycles with electronic ones, improving the fuel quality, using alternative fuels including compressed natural gas and liquid petroleum gas, installing catalyst converter on gasoline engines, and traffic management plans, including the development of clean public transport and LEZ can cut air pollution.

Among the aforementioned effective solutions, installation of a catalyst converter on gasoline engines and improving the fuel quality have been the most effective in the country, in the metropolis of Tehran, however, other solutions have faced barriers and not achieved any good results since past few years, he added.

The LEZ scheme, which is one of the successful methods taken up in European countries, was taken into consideration in Iran as well, but it has been revised and changed after a time, and finally obligatory vehicle inspection approach went into effect, so that vehicles not undergoing an annual quality inspection are fined, he highlighted.

To measure the scheme’s effectiveness, there are several main criteria which demonstrates how inspection affects reducing the PM emissions haunting the capital, he further said.

The first criterion refers to the car owner’s participation rate, many car owners in the capital do not pay attention to the laws and some are unaware, Kazemi stated.

New cars under four years of age are exempted from the vehicle inspection law, which constitute some 25 percent of the whole vehicles running in Tehran, while about 15 percent of the heavy-duty vehicles did not refer to technical inspection centers at all, he lamented.

Pointing to cars with major defects as the second criterion, he stated that in the current autumn, some 546,000 cars have undergone quality inspection, out of which some 114,000 have been rejected to receive an inspection sticker. 

Statistics show that about 20 percent of the vehicles referred to the inspection centers have failed in quality inspection, he noted.

Kazemi also added that repair and renovation of the emission producing cars is the third criterion for the LEZ scheme proficiency evaluation, given the high costs of repair, some car owners decide to avoid the expenses and repair some minor defects.

In order to prevent such repairs, inspection tests have been conducted for heavy-duty vehicles on the roadsides, through which diesel vehicles have been technically tested, regardless of having inspection stickers, he noted, lamenting, 30 percent of the cars failed the tests despite having inspection label.

Considering the three main criteria in assessing the LEZ scheme, only 1.5 percent drop in PM 2.5 concentration is measured, he said.

So, expecting the scheme to mitigate the whole air pollution is a misconception, and it is necessary to improve the scheme in order to increase its effectiveness, he concluded.

World Health Organization (WHO) asserts that Tehran is one of the most air polluted cities in the world. Tehran is ranked 12th among 26 megacities in terms of ambient PM10 levels. After Cairo, Tehran is the most polluted non-Asian megacity. In 2016, the annual ambient level of PM10 was estimated at 77 micrograms per cubic meter. This is almost four times the WHO’s recommended threshold of 20 micrograms per cubic meter.

According to a report by World Bank published in April 2018 there are about 4.24 million vehicles in Tehran. Cars are the largest vehicle type, with a total fleet of 3.37 million, or 80 percent of all vehicles. The second largest category, in terms of sheer numbers, are motorcycles, amounting to a total of 0.76 million, or 18 percent of total vehicles. The smallest category is heavy-duty vehicles, with a total of 0.1 million vehicles, or about 2 percent of total vehicles in the streets of Tehran.

Even though cars are the most abundant and the most congestion-causing vehicle type on the streets of the capital, they only contribute about 3 percent of the city’s mobile PM pollution. Similarly, despite motorcycles being the most pollution intensive vehicle per passenger, they only contribute to about 12 percent of the total mobile PM emissions. 

In turn, heavy-duty vehicles contribute about 85 percent to mobile PM emissions. Amongst heavy-duty vehicles, private sector buses (35 percent), followed by Tehran municipal buses (28 percent), and trucks (28 percent), contribute the largest shares to the pollution load. Heavy-duty vehicles mostly run on diesel, which has a much higher PM emissions factor than petroleum or natural gas.

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