PHILADELPHIA – Philadelphia cabs went on strike May 16 to protest the use of GPS units to track passenger movements and issue speeding tickets to cabbies, according to the Web site www.thenewspaper.com. The Philadelphia Parking Authority (PPA) recently gave a $4.1 million black box contract to Taxitronic Inc, a company that makes the “eTrack” GPS unit for $2,600. eTrack provides real-time vehicle location, direction, speed, status (vacant/hired), etc. Cab drivers would be required to pay for installation, maintenance, and $18 monthly fee for the device starting Oct. 10. The new system will also change the way taxis operate in the city, as residents would have to call a cab by going through the dispatch system and not having the option to hail them on the street. The city will collect a $250 fine from any driver who refuses to go to a dangerous location in the city.