Scores of illegally parked vehicles — most driven by city workers and contractors — in downtown Brooklyn are brazenly flouting the law, prompting “dangerous” road conditions for passersby, a new bombshell report revealed. A survey released Monday by City Councilman Lincoln Restler’s office found an average of 457 illegally parked cars daily across 60 blocks of downtown Brooklyn, between May 26 and June 20, using government placards, phony placards or signs like NYPD vests — with only 3% ticketed.