Public transit service frequency and fares with heterogeneous users under monopoly and alternative regulatory policies

•A model of public transit service under monopoly with heterogeneous users is presented.•A general condition under which the Mohring Effect exists is derived.•A formula for the cost recovery ratio under marginal-cost pricing is derived.•Profit-maximizing and social-surplus-maximizing frequency decisions are compared.•Transit operations under four types of regulations are analyzed and compared quantitatively.