While doing so, the mayor defended the police who he said are pushed by threats of charges for pursuing rogue drivers.
In angry statements during the turnover of 13 police patrol cars donated by the city government to the Davao City Police Office on Wednesday, Duterte said the city's taxi force has been penetrated by criminals pretending to be drivers preying on Dabawenyos and their visitors.
He said they are actually criminals who commit violence and extortion.
Some of these drivers pick up passengers from Davao International Airport, Duterte said, but order their passengers to disembark if they don't agree to pay exorbitant taxi fees.
Some taxi cabs along the alley line at the DIA duck the required meter system in place of "pakyaw" fees.
The mayor, who was a city prosecutor before becoming mayor in 1988, stressed that those who do so should be arrested for committing estafa.
Duterte assailed that the drivers even threaten policemen of being sacked once they are trailed for their modus operandi.
The mayor lambasted investigators and lawyers who he said jump at filing charges against supposedly erring policemen.
He also warned taxi operators of condoning their taxi drivers when they are caught committing violations.
The mayor ordered the police to enforce the wearing of identification cards and uniform among the taxi drivers.
Duterte appealed to the passengers to look at the compliance of taxi drivers of minimum identification requirements such as ID cards and uniform.
He also urged the police to be relentless in pursuing the criminals despite threats of charges. "Do not be afraid. Do not be intimidated by the filing of cases," he said.
Then to the criminals in the taxi system he warned, "Those of you who threaten policemen, once I could sense you, if I can find you, you will have to deal with me."
Duterte said those who have complaints against erring policemen shall have to approach him personally.
Likewise, he warned policemen the city of Davao is no place for abusive cops.