The initials PLPD stand for "public liability and property damage," which is essentially the same as bodily injury and property damage (BI and PD) liability insurance. The basic concept of public liability in terms of car insurance is it would cover you in the event that your vehicle causes injury or death to a third party and property damage is if your car damages someone else's property.
This acronym of P.L.P.D. is commonly used by a person, usually from Michigan, when they are stating they have a "bare bones" auto insurance, though the insurance type it is referring to has been out of date for nearly 30 years in Michigan. In the early 1970s MI changed over to a no-fault system with different insurance requirements.
The insurance term PLPD may be used today by many that are saying that they have satisfied their obligation to their state insurance laws by having the minimum state required liability limits of auto insurance on their vehicle. This type of insurance coverage offers third party coverage but offers no coverage to your vehicle's damage in an accident.
Public liability and Property Damage (PLPD) is not only a term used in Michigan. PLPD is still required in some states for certain motorists. For example in Washington State motor carrier drivers must obtain public liability and property damage insurance covering each motor vehicle that they use to transport household goods.