Bus operators screamed “harassment” and blocked traffic to and from Howrah on Thursday after officials stepped up their drive against resoled tyres that form a fatal combination with rash driving.

Around 20 buses plying on the Howrah-Calcutta route were “booked” and fined for using “unsafe” resoled tyres, prompting the drivers to park their vehicles across the road near Howrah Maidan.

Some drivers and owners allegedly pushed and shoved officials of the regional transport office’s enforcement wing during the protest.

“We have barely penalised 40 buses since Wednesday and they (bus operators) are already up in arms. It shows how intolerant they have become of any attempt to enforce rules,” said Chandan Sen, an official involved in the crackdown.

Traffic on either side of Howrah bridge and Bankim Setu, from where a minibus plunged 35 feet onto rail tracks last Saturday killing 12 passengers, was paralysed from 2pm to 3.30pm because of the protest. Schoolchildren going back home and train passengers headed for Howrah station from the city bore the brunt of the blockade.

Surajit Saha, who owns a bus on the Howrah Maidan-Baishnabghata route, claimed that the crackdown on resoled tyres was an eyewash. “The very people who accept bribes to issue fitness certificates are now penalising us for using resoled tyres. Why don’t they (transport officials) check state buses that use the same kind of tyres?” he asked.

The Motor Vehicles Act does not contain any clause on resoled tyres, leaving it to officials to interpret what is safe or unsafe.

A traffic police officer in Lalbazar said vehicles were free to use a resoled tyre as long as the condition of “the unit as a whole” was good. “A worn-out surface can be given a new strip of rubber grips but the overall structure must be strong. Most buses make do with patchwork on the tyres, which is unsafe and, therefore, illegal,” he explained.

Bus owner Saha said the police and the transport office’s resoled tyre rules lacked clarity. “The crackdown is illegal, not our resoled tyres.”

The bus lobby has also picked holes in the transport department’s notification on the use of speed governors. “The notice does not specify the brand or make of speed governors that are to be used. If we spend money on a particular brand but are refused a fitness certificate, what will we do?” asked Jayanta Chatterjee, the secretary of the Joint Committee of Passenger Transport.

The method of checking whether a speed governor fitted to the engine works is another grey area. “None of the regional transport offices in the state has the equipment and the expertise to carry out the checks,” said transport consultant S.M. Ghosh.

In Karnataka, truckers had struck work twice earlier this year after the high court made speed governors mandatory on highways while hearing an accident-related case.