The running battle on the street from Technical intersection to Gabtoli, one of the main accesses to the capital, has continued with pauses since 8pm on Tuesday.
Police fired teargas in response to arson attacks by the workers, who have also been pelting brickbats at them.
Three constables and a passerby were taken to Dhaka Medical College Hospital around 11:30pm after sustaining injuries during the clashes.
Injured Constable Anik Chakrabarty, 22, told reporters that they were injured when a bomb went off in front of them.
The demonstrators later torched a truck near the entrance to Mazar Road.
bdnews24.com staff member Billal Hossain saw a microbus was vandalised around 9:30pm.
Earlier, around 8pm, a police wrecker and a temporary police box were torched during the clash in front of Inter-District Transport Workers' Union office, witnesses said.
Many of those, who were walking into the capital, said hundreds of vehicles have been stranded at the entrance of the city due to the clashes.
The workers have been demonstrating in front of the union office since morning. Their number grew in the evening.
The angry workers blocked the street at one stage and police tried to stop them, which led to a pitched battle, witnesses said.
Darussalam Police Station OC Selimuzzaman claimed to have the situation under control around an hour after the violence started.
He said the workers set fire to 'only a wrecker'.
A bus worker, 'Alam', said the workers burnt a police box down in front of Hanif Paribahan counter at Balur Mathh.
Aslamul Haque, who represents the area in Parliament, went to calm the agitated transport workers but failed to get them off the street.
He blamed the BNP for the clashes, which he said, are part of 'fire-terror', a term often used by ruling Awami League leaders to describe violent protests by the main opposition party outside Parliament.
Transport workers in Chuadanga first began the strike action.Those in the 10 districts of Khulna division joined them on Sunday.
The strike and demonstrations spread across the country on Tuesday morning following the sentencing of a truck driver on Monday for running over and killing a woman in Savar.