All are free to park their vehicles at public parks but that does not necessarily imply the cost of such parking should be made free to all. The park is a public good in that it's provided without any charge and profit for the well-being of the community as a whole. Vehicle parking facilities in parks, however, are by definition not in the same category - as many, like pedestrians, might derive no benefit, and usage is not what economists term "non-rivalrous", meaning that usage by some does not reduce its availability to others.
Parking spaces, however, are used on a competitive basis. And when demand is keen in some areas, a first-come-first-served ethic would not assuage park users who believe spaces are being taken up by commercial or passenger vehicles left there for long periods by those working or living nearby. Such misuse is one of the reasons behind the National Parks Board's (NParks') decision to install automated parking systems at 18 carparks in 12 parks, including East Coast Park, Bishan-Ang Mo Kio Park, Woodlands Waterfront Park and Labrador Nature Reserve.
Paid parking is also an accepted means of regulating heavy demand. However, that logic starts to fray when demand fades significantly at certain times, yet charges remain the same. Parks constitute havens amid the bustle where all are free to enjoy moments of simple bliss, either relaxing or exercising. Motorists accustomed to free usage over many years are not surprisingly ruffled by having to pay parking fees now. NParks can ease that discomfort by adopting a tiered system of charges instead - for example, offering free use for the first hour in all but the busiest parks and lower rates during non-peak hours.