Calcutta University and many other educational institutions also cancelled the exams that were scheduled to be held Friday.

Although the strike is indefinite in the Kolkata Metropolitan Area (KMA), operators in the rest of the state have called for a day's strike Friday.

The Calcutta High Court July 2008 ordered a ban on commercial vehicles registered before Jan 1, 1993, from Kolkata and its outskirts. It said the order should be implemented by Dec 31, 2008, in the Kolkata Metropolitan Area (KMA), which includes parts of North and South 24-Parganas, Howrah and Hooghly districts.

Later, the date for imposing the ban was put off till July 31, 2009, following a state government plea.

The state government decided to phase out old vehicles from July 25 to implement the court order.