A smoke-belching two-stroke autorickshaw at Park Circus on Tuesday afternoon. Picture by Sanat Kumar Sinha

The last day of the year is also the last day a two-stroke autorickshaw can legally ply on a Calcutta street. But with the government in no mood to meet the deadline and the auto brigade eyeing exit routes, the onus is on we the people of Calcutta to enforce the high court ban that everyone else is trying to dodge.

Here’s a Metro guide to help commuters make an informed choice from January 1.

How can I distinguish between a two-stroke and a four-stroke auto?

Look out for the sign 2RE/RE 2stroke in the front or the rear of the vehicle. A four-stroke auto will have 4 RE/RE 4stroke embossed on it, indicating its engine configuration. Older two-stroke autos might not have any mark.

Unless modified, the diameter of the exhaust pipe will also give a two-stroke auto away. The exhaust pipes are cylindrical and larger in four-stroke engines.

Unless modified, two-stroke autos only have hand starters. Four-stroke autos have both ignition switches and hand starters.

The easiest way to spot an old two-stroke auto is, however, by its appearance. It will look its age.

How do I know during a ride that the auto has a two-stroke engine?

The engine will be noisy and vibrate more than a four-stroke three-wheeler. If the auto is running on adulterated fuel, better known as katatel, the fumes emitted through the tailpipe will be hard to miss.

How many two-stroke autos ply in Calcutta?

Around 38,000 registered autos operate in greater Calcutta. Another 30,000 autos ply illegally with union backing.

How does the presence of two-stroke autos on the streets of the city affect me?

They are two-stroke terrors, poisoning the air you breathe. Two-stroke autos running on petrol emit carbon monoxide and hydrocarbon, which can affect your lungs, heart, kidney and eyes. Autos that use katatel emit tonnes of particulate matter and nitrogen oxides as well, putting your health at even greater risk.

Is conversion to LPG the answer?

Only if the age limit permits. Autos that are over 15 years old have been banned in cities like Delhi and Mumbai. According to an Asian Development Bank study in 2005, around 83 per cent of the three-wheelers (including goods vehicles) in greater Calcutta have been on the road for 20 years or more. So, conversion to LPG is not the answer for the city’s aged fleet of two-stroke autos.

What can happen if I board a banned auto?

Commuters can’t be prosecuted. But you should feel a pang of guilt for contributing to the flouting of a high court ban and for boarding a vehicle contributing to the city’s poison air that maims and kills.

What can I do to stop a two-stroke auto?

You can approach the nearest traffic sergeant or lodge a complaint with the nearest police station, says police commissioner Gautam Mohan Chakrabarti.

You can take it a step further by filing a contempt of court case, says high court advocate Kallol Guhathakurta.

What is the role of cops?

Police can crack down on two-stroke autos without waiting for the public vehicles department (PVD) to act. Officers of the traffic police department can seize a two-stroke auto and initiate legal action. Till Tuesday evening the police were still waiting for the PVD to take a call and show the way.

What is the PVD doing?

Precious little. The department plans to deploy personnel to trace and seize banned autos. Garages where two-stroke autos are parked won’t be raided, at least for now.

Bajaj Auto Ltd, the manufacturer of most autos running in Bengal, sent a note to the PVD last Saturday on how to identify two-stroke and four-stroke autos by checking the chassis and engine numbers. The company appended a list of chassis and engine numbers of autos manufactured by it and distributed across Bengal.

How can the ban on two-stroke autos be implemented? Tell ttmetro@abpmail.com