What can I say, niky is right on the money.
And that decal/badge/marking is not only for being exempt from the UUVRP. For three generations, all of our vehicles have worn a badge to identify it as a doctor's vehicle. Eh, wala naman UUVRP noong 1946 diba?
One of the reasons for marking a doctor's vehicle is that the law, at least in writing, guarantees the doctor's vehicle the same rights as a fully-marked ambulance when responding to a medical emergency. As early as the second year of medical school, this will be taught already under the subject of Legal Medicine.
As for abuse, yes it is open to abuse. But would you waste more than 10 years of your life trying to be a doctor just to be exempted from the color coding? Maglagay ka na lang ng decal ng pulis o kaya TV station!
The only 'doctor' I know that loved abusing the UUVRP was NTV-777, and he got out of med school by the 2nd year so I don't think he counts.