Vehicle positioning system using location codes in passive tags
Vehicles driving on a roadway interrogate passive tags in or on lanes of the roadway. Codes in the tags represent locations along the highway and which lane the vehicle is traveling in. Units in the vehicles communicate longitudinal and lane positions derived from the codes among each other or with infrastructure units for purposes such as traffic management, alerts concerning other vehicles, alerts concerning external conditions, or traffic control. The units may also communicate vehicle lengths or other parameters or characteristics. Vehicle units may communicate with sensors and actuators in the vehicles for purposes such as updating the vehicles' positions between adjacent tags. Specific applications for intelligent transportation systems are described.
1. A method performed in an infrastructure unit, comprising:
receiving a plurality of radio frequency messages from a plurality of vehicles, the messages corresponding to longitudinal locations of vehicles along a roadway and lanes of the roadway occupied by the vehicles;
calculating a function from the longitudinal locations and the lanes;
performing an action in response to the function, wherein the action concerns controlling a traffic signal.
2. A method performed in an infrastructure unit, comprising:
receiving a plurality of radio frequency messages from a plurality of vehicles, the messages corresponding to longitudinal locations of vehicles along a roadway and lanes of the roadway occupied by the vehicles;
calculating a function from the longitudinal locations and the lanes;
performing an action in response to the function, wherein the action concerns controlling a signal for a turn lane.
3. A method performed in an infrastructure unit, comprising:
receiving a plurality of radio frequency messages from a plurality of vehicles, the messages corresponding to longitudinal locations of vehicles along a roadway and lanes of the roadway occupied by the vehicles;
calculating a function from the longitudinal locations and the lanes;
performing an action in response to the function, wherein
one of the messages contains data indicating that the sender is an emergency vehicle,
the function concerns a distance of the emergency vehicle from the signal,
the action controls the signal so as to facilitate passage of the emergency vehicle.
4. A method performed in a vehicle on a roadway having a designated toll lane and at least one other lane in the same direction as the toll lane, comprising:
interrogating a sequence of passive roadway tags so as to receive a location codes representing a longitudinal location and a lane code representing the toll lane when the vehicle occupies the toll lane;
maintaining a log representing a cumulative distance in which the vehicle occupies the toll lane;
communicating data representing the cumulative distance to an infrastructure unit at a predetermined place along the roadway.
5. The method of claim 4 further comprising detecting an end-of-toll lane code in one of the passive roadway tags located at the predetermined place, and where the data is communicated in response to detecting the end-of-toll-lane code.
6. The method of claim 4 where the data is communicated by a programmable RFID tag in the vehicle.