This paper proposes a pricing framework for controlling the charging demand of electric vehicles (EVs) in coupled power and transportation systems. Specifically, we develop a service area partition method based on a biased min-consensus algorithm, which enables us to estimate the charging requests of EV drivers. Then, to control the charging requests of EV drivers, we introduce the concept of safety penalty into the travel cost of EV drivers. The optimal charging demand profile is obtained by solving a safety-constrained optimal power flow problem that aims at minimizing the voltage deviation. The safety penalty is designed based on a closed-loop Proportional-Integral controller to make the charging requests of EV drivers trace the optimal charging demand profile. A numerical study designed on the city map of Shenzhen demonstrates the effectiveness of the control framework.