Having a clear majority in the house makes it relatively easy to take controversial decisions. This is what Delhi Chief Minister Arvind Kejriwal of the Aam Aadmi Party, which holds 67 of 70 seats in the house, seems to have learned from the first phase of the odd-even scheme in January. His plan for reducing the capital's throat-searing pollution levels was simple – allow private cars to use to the streets only every other day.

Except that it is no longer working.

After declaring the odd-even plan a roaring success when it was introduced for a 15-day trial in January, Kejriwal later had to accept that the emergency measure put in place to combat noxious air actually had a greater impact on traffic congestion. But that didn’t stop him from announcing a second 15-day phase for the odd-even scheme in April. It got over on April 30 – and the preliminary results are disappointing, to say the least.

Nobody was expecting the Delhi air to get a whole lot cleaner merely with the introduction of restrictions on private cars, which make up for about only 15% of the total trips in the capital. But it turns out that pollution levels actually increased in the second half of April. According to data generated by IndiaSpend’s air-quality monitoring sensors, pollution rose 23% during this period.

There are no easy explanations about why pollution levels showed an increase if there were indeed fewer cars on the road. The 15-day average of PM 2.5 concentration in the air rose sharply during the second phase of odd-even, as shown in the chart above.

The data seems to point to the obvious conclusion that factors such as truck emissions, factory pollution and dust have a more profound impact on air-quality in the capital than emissions from cars.

Moreover, the worst hourly average of PM 2.5 concentration were observed in the capital at 7 am. Pollution so early in the morning when a substantial number of cars are off the road implies that more comprehensive steps need to be taken to control pollution than just restricting cars.

During the first 10 days of the April leg of odd-even, the police issued a lower number of challans compared to the first phase. This could point to higher compliance by drivers. However, it could also be because the police were stretched thin, also checking violations such as cab drivers charging surge prices or those running diesel cabs on the periphery of the city.

What most road users agree on is that the congestion was not really any better.

On Monday, April 18, the number of cars passing through Delhi-Noida-Direct flyway reduced by 6% – a negligible figure if one considers the severity of congestion in Delhi where cars occupy 90% of the road space.

However, preliminary data collected for a Massachusetts Institute of Technology research project suggests otherwise. It selected around 1,000 drivers in the capital at random and used data from Google maps and phone surveys to evaluate the effectiveness of the odd-even scheme.

Their findings reveal that only 7.9% of the respondents complained of congestion during restricted days while the number was as high as 27.2% in the week before the plan came into place.

A possible explanation for this is the astute nature of Delhiites, who adapted to the scheme’s restrictions quite well. The study shows that close to 19% of their respondents switched to using a second car to commute in April, while only 6% did so in January. The use of two-wheelers declined while use of taxi and auto-rickshaws to commute remained the same during the two phases of odd-even.

There are concerns within the government that the exemption provided to CNG vehicles is being misused. Last week, it launched a drive to verify the authenticity of CNG stickers on cars with the suspicion that some drivers may have obtained the stickers illegally. However, no violators were found during the checks.

In the first phase of the scheme, Indraprastha Gas Limited had issued CNG stickers to about 4 lakh vehicles, even as these were found to be sold in grey market for Rs 2,800 each.

Even without having CNG stickers on their car, some Delhiites used their cars to commute by identifying “safe routes” near their homes and localities where they presumed there would not be any police presence, according to the MIT study. Others said that they travelled around the 8 am-8 pm restriction. But 35% chose not to respond to the question.

This is perhaps why Delhi needs to go beyond odd-even – the scheme stopped working because drivers seem to have found workarounds to diminish whatever little impact it was having on pollution. Sunita Narain, the director of Centre for Science and Environment has already appealed to the Delhi chief minister to treat odd-even rule only as an “emergency measure”. Instead, Delhi needs a “basket of measures”, she said.

She added: “We can’t underestimate the role of vehicles but we have to control trucks and two-wheelers as well to combat pollution.”