They said the amount of bribe is fixed and they are forced to pay despite possessing legal documents, including licence, route permit and fitness certificate.

The owners usually pay Tk 500 for a bus and Tk 1,000 for a truck or a covered van. The amount of extortion increases if any document is missing.

Transport sector sources said the collected tolls are distributed from traffic sergeants to deputy commissioners of the traffic department.

When asked, Deputy Commissioner (North) of DMP Feroz Al Mujahid Khan however put the blame on transport associations for the extortion.

He told Star City that a section of transport owners' and workers' organisations are involved in collecting tolls from vehicles. "We file cases if the traffic rules are violated. We seize vehicles for plying without route permits."

"If there is any specific allegations on extortion by police, I will try to take action," he said.

The bribes are collected at Mohammadpur, Mirpur, Dhanmondi, Ramna, Tejgaon, Demra, Sutrapur, Kotwali and Gulshan. These points are called "ghats."

According to Bangladesh Road Transport Authority (BRTA), some 4,000 buses and minibuses, 1,700 human hauliers and taxicabs now ply on the city routes.

However, officials at the Dhaka Urban Transport Coordination Board (DTCB) and the traffic division of Dhaka Metropolitan Police (DMP) said the number of buses is 5,800.

According to the Association of Bus Owners (ABC), 34 bus companies provide transport services along the city's 63 routes. All of them are forced to pay the monthly bribe, otherwise they face different types of harassment, sources said.

"If I do not pay, the police will file cases using lame excuse that costs more than the amount of bribe," said a bus company owner, seeking anonymity.

"If the police officers know that I have complained, they will either increase the amount of bribe or withdraw my bus from the road using a lame excuse," he alleged.

Sources said Mega City Bus Company Ltd pays bribes of around Tk 50,000 a month for running buses on Mohammadpur-Motijheel and Shyamoli-Motijheel routes.

Another bus company, ATCL, pays Tk 28,000 for route numbers 12A and 12B Mohammadpur-Farmgate and Mohammadpur-Science Laboratory-Motijheel.

Rajdhani Express, another bus company that operates services from Mohammadpur to Motijheel, pays Tk 12,000 a month.

The owner of a reputed bus company admitted that the buses are allowed to run on specific routes in the city but they can also operate the buses on unauthorised routes paying extra amount of bribe to the traffic police.

"The police take about Tk 128,000 in bribe from the buses plying through the Mohammadpur routes," claimed a top-ranking leader of a transport association.

Some 150 buses and 225 minibuses ply on these routes.

Many buses plying on the Mohammadpur-Science Laboratory-Motijheel route, covering Nilkhet, Shahbagh and Motijheel, have no route permit, sources said.

Sources in the DMP said each traffic sergeant has to file at least five cases a day against the rules violators and fine them to show police activities in the field. It is said that private buses and minibuses are their prime targets.

High officials in the traffic division said the traffic police collect on average Tk 60 lakh every month as fine for violation of traffic rules. In April, the north zone of DMP traffic collected Tk 42 lakh and south zone Tk 36 lakh.

Many bus owners said the sergeants often pretend to file a case to collect money. "Actually, he will not file a case. He wants bribe," a bus owner alleged.