Computer-implemented predictions of upcoming traffic control signal states or state changes can be used to improve convenience, safety, and fuel economy. Such information can be used advantageously by a human operator, or by an autonomous or semi-autonomous vehicle control system. User (for example, driver) requests for a signal change may be implemented in traffic control systems, with all due care. User requests are validated and compared to traffic signal state change predictions. Only when appropriate conditions are met, the user request is used to generate a “synthetic call” to the applicable traffic signal controller (TSC). The new synthetic call substitutes for the usual call signal which arises from a fixed physical hardware detection system such as an inductive loop in the pavement.