Traffic in the Bangladeshi capital Dhaka is at a standstill for an average of 7.5 hours a day, according to a government study that highlighted the huge economic toll of congestion.

"Dhaka is perhaps the worst congested city in the world. It is fast becoming unlivable," Santosh Kumar Roy, an engineer with the Roads and Highway Division which conducted the study, said Monday.

"Tailbacks are becoming bigger and bigger," he said. "We have found that between 8:00 am and 8:00 pm, a vehicle spends on average 7.5 hours in traffic jams."

The annual economic loss from the gridlock on Dhaka's four key roads alone amounted to 96 billion taka (1.4 billion dollars) -- one-third of the impoverished country's annual development expenditure, the study found.

According to the Bangladesh Road Transport Authority, in 2008 nearly 20,000 new vehicles hit the streets of Dhaka, which has grown from a population of 200,000 in 1974 to 12 million today.

Last year the government launched a 20-year plan to transform the city's transport network, including building a metro system, but work has yet to begin.