Black cab drivers in Birmingham have started a nine-day "go slow" protest against proposed clean air zone charges in the city centre.
Drivers of high-polluting cars will have to pay £8 to travel in the city centre after the government approved the city's clean air zone (CAZ) plan.
Birmingham's RMT union said it wanted more than the £5,000 the city council was offering drivers to upgrade cabs.
The council said government funding would help support taxi drivers.
Cabbies will drive slowly through the city centre at peak times for two hours each day of the protest, but say they will call it off if the council agrees to talks.
Birmingham City Council was given £38m by the government towards the cost of the CAZ, of which £15m has been pledged to help black cab and private hire drivers, including bursaries for new electric vehicles or retrofit solutions.
RMT wants more funding for compliant vehicles and also said the proposed CAZ charge for taxi drivers should be dropped.
Birmingham's union branch secretary Raja Amin said drivers were in favour of the zone "but not at our expense - we're already hard-pushed".
The £5,000 for each black cab driver to put towards adapting their existing vehicle or buying a new one, was "not enough", he said.
There have been "no meaningful discussions or negotiations" with the council, he said.
Cabbies at the taxi-rank outside the Bullring and New Street Station told the BBC they felt the council was "not concerned" and "has not thought" about them.
After the protest caused long tailbacks and brought the Holloway Head roundabout to a standstill, West Midlands Police said it would send officers to Wednesday's demonstration.
"Drivers who deliberately cause obstructions will be dealt with appropriately," the force said.
The CAZ is due to begin in January 2020 and would affect diesel cars manufactured before 2015 and petrol cars made before 2006 driving inside the A4540 ring road.
The charge will be £8 for cars and £50 for buses and HGVs.
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