Calcutta: Trucks have been banned from four flyovers and bridges in Calcutta after being found to be the weakest among the nine that were under the scanner since a portion of Majerhat bridge collapsed five days ago.

The government on Saturday said heavy goods vehicles would not be allowed on Tollygunge bridge and Bijon Setu in south Calcutta and Belgachhia bridge and Aurobindo Setu in the north with immediate effect.

"We are putting restrictions on the movement of any kind of goods vehicles on these four bridges as we want to strengthen the bridges first. We will allow (goods) vehicles after the strengthening work," Rajeev Kumar, the commissioner of Calcutta police, said.

The decision to ban heavy goods vehicles from four of nine flyovers and bridges was taken after the urban development and public works departments conveyed to the government that the structural stability of these structures would be heavily compromised if subjected to continuous heavy load.

Consulting agency Rites had flagged the lowered load-bearing capacity of Aurobindo Setu, which connects Ultadanga and Gouribari, in April. A report said that the bearings of the flyover had not been replaced for decades, putting the stability of the structure at risk.

Bearings are placed between the deck of a flyover and its piers to ease the stress on the structure with controlled movement.

Aurobindo Setu's deck rests on 40 to 45 bearings, all of which have exceeded the stipulated replacement date. With little or no maintenance, the 43-year-old bridge is in the "high-stress" category, according to the Rites report that was submitted to the Calcutta Metropolitan Development Authority.

But until the Majerhat bridge collapsed last Tuesday, no government agency seemed bothered about taking corrective action.

The nearly kilometre-long Belgachhia bridge connecting Shyambazar and Jessore Road flaunts a coat of blue-and-white but its underside shows poor upkeep. Like Majerhat, a canal below has made the pillars vulnerable to subsidence if exposed to continuous excess load.

Bijon Setu, connecting Gariahat and Kasba, has trees and creepers growing out of crevices on the sides of the deck slab. A fresh coat of paint seeks to hide the warts on the bridge named after Bijon Basu, an executive engineer with the erstwhile Calcutta Improvement Trust.

Tollygunge bridge, linking Tollygunge Circular Road with Tollygunge Phari, runs over the Adi Ganga and is more than 80 years old. It was painted five years ago but has never had thorough maintenance, an engineer said.