This invention provides an apparatus for stopping the idling of an automobile engine, a system for relating the apparatus to a traffic signal device and further a signal display apparatus for supplying a driver information such as idling stop of the automobile engine and the like in relation to the system in order to prevent generation of exhaust gases caused by unnecessary engine idling when an automobile is stopped at a traffic signal and the like. A period of time t s corresponding to the period of time until the traffic signal of a traffic signal device is changed to green is calculated based on a signal received from by the traffic signal device. A period of time T, which serves as a base for determining whether idling is to be stopped or not, is determined based on the calculated period of time t s . The idling of the automobile engine is stopped only when the period of time T satisfies a predetermined condition. When the idling of the automobile engine is stopped, the engine is restarted after the period of time T.