Route Guidance System

A route guidance system comprising an in- vehicle device and a central route advisory system in which the in-vehicle device comprises audio and visual units which provide instructions, e.g. pictographs, to a user to perform manoeuvres required to complete an optimal route. The optimal route is determined by the central route advisory system using real-time and historical traffic data acquired from monitored routes together with static typical traffic information acquired from non- monitored routes and transmitted by the central route advisory system to the in-vehicle device in response to a route request from the user to the central route advisory system to a specified destination. A call line identity of a user's device can be received at the advisory system and the user's current position may be determined by a dual tone multifrequency (DTMF) transmission. A traffic forecasting model may be used to determine an optimal route.