Use of relationship between activities of different traffic signals in a network to improve traffic signal state estimation

1. A method comprising:

determining, using a computing device, that a vehicle is approaching an upcoming traffic signal;

in response to determining that the vehicle is approaching the upcoming traffic signal, requesting, using the computing device, a state of one or more traffic signals other than the upcoming traffic signal;

subsequently receiving, by the computing device, the state of the one or more traffic signals other than the upcoming traffic signal; and

determining, using the computing device, an estimate of a state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal and the state of the upcoming traffic signal.

2. The method of claim 1 , further comprising receiving the state of the one or more traffic signals other than the upcoming traffic signal from one or more other vehicles.

3. The method of claim 2 , wherein the state of the one or more traffic signals other than the upcoming traffic signal comprises an observed state of the one or more traffic signals obtained by the one or more other vehicles.

4. The method of claim 1 ,

wherein the state of the one or more traffic signals other than the upcoming traffic signal comprises a state determined based on sensor data obtained from one or more sensors of the vehicle.

5. The method of claim 1 , further comprising receiving the state of the one or more traffic signals other than the upcoming traffic signal from one or more fixed sensors in an environment.

6. The method of claim 1 , further comprising determining the estimate of the state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal, the state of the upcoming traffic signal, and the time of day.

7. The method of claim 1 , further comprising the computing device sending the estimate of the state of the upcoming traffic signal to another device.

8. The method of claim 7 , wherein the another device is configured to control the vehicle in an autonomous mode.

9. The method of claim 7 , further comprising:

determining another estimate of when the state of the upcoming traffic signal will change; and

sending the another estimate to the another device, wherein the another device comprises a driver assistance system.

10. A non-transitory computer-readable medium having stored therein instructions executable by a computing device to cause the computing device to perform functions comprising:

determining that a vehicle is approaching an upcoming traffic signal;

in response to determining that the vehicle is approaching the upcoming traffic signal, requesting a state of one or more traffic signals other than the upcoming traffic signal;

subsequently receiving the state of the one or more traffic signals other than the upcoming traffic signal; and

determining an estimate of a state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal and the state of the upcoming traffic signal.

11. The non-transitory computer-readable medium of claim 10 , wherein the functions further comprise receiving the state of the one or more traffic signals other than the upcoming traffic signal from one or more other vehicles.

12. The non-transitory computer-readable medium of claim 11 ,

wherein the the state of the one or more traffic signals other than the upcoming traffic signal comprises on an observed state of the one or more traffic signals obtained by the one or more other vehicles.

13. The non-transitory computer-readable medium of claim 10 , wherein

the state of the one or more traffic signals other than the upcoming traffic signal comprises a state determined based on sensor data obtained from one or more sensors of the vehicle.

14. The non-transitory computer-readable medium of claim 10 , wherein the functions further comprise receiving the state of one or more traffic signals other than the upcoming traffic signal from one or more sensors in an environment.

15. The non-transitory computer-readable medium of claim 10 , wherein the functions further comprise determining the estimate of the state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal, the state of the upcoming traffic signal, and the time of day.

16. The non-transitory computer-readable medium of claim 15 , wherein the functions further comprise sending the estimate of the state of the upcoming traffic signal to another device.

17. A controller comprising:

at least one processor;

a memory; and

instructions stored in the memory and executable by the at least one processor to cause the controller to perform functions comprising:

determining that a vehicle is approaching an upcoming traffic signal;

in response to determining that the vehicle is approaching the upcoming traffic signal, requesting a state of one or more traffic signals other than the upcoming traffic signal;

subsequently receiving the state of the one or more traffic signals other than the upcoming traffic signal; and

determining an estimate of a state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal and the state of the upcoming traffic signal.

18. The controller of claim 17 , wherein the functions further comprise receiving the state of the one or more traffic signals other than the upcoming traffic signal from one or more other vehicles.

19. The controller of claim 18 , wherein the state of the one or more traffic signals other than the upcoming traffic signal comprises on an observed state of the one or more traffic signals obtained by the one or more other vehicles.

20. The controller of claim 17 , wherein

the state of the one or more traffic signals other than the upcoming traffic signal comprises a state determined based on sensor data obtained from one or more sensors of the vehicle.

21. The controller of claim 17 , wherein the functions further comprise determining the estimate of the state of the upcoming traffic signal based on a relationship between the state of the one or more traffic signals other than the upcoming traffic signal, the state of the upcoming traffic signal, and the time of day.

22. The controller of claim 17 , wherein the functions further comprise:

determining a location and direction of the vehicle; and

determining that the vehicle is approaching the upcoming traffic signal based on the location and direction of the vehicle and known locations of a plurality of traffic signals.

23. The controller of claim 17 , wherein the functions further comprise sending the estimate of the state of the upcoming traffic signal to another device.

24. The controller of claim 23 , wherein the another device comprises a driver assistance system.

25. The controller of claim 23 , wherein the another device is configured to control the vehicle in an autonomous mode based on the estimate of the state of the upcoming traffic signal.

26. The controller of claim 23 , wherein the functions further comprise:

determining another estimate of when the state of the upcoming traffic signal will change; and

sending the another estimate to the another device.