Traffic Light Sync Problems in WOMD and Waymax Simulation

[vcharraut]

There appears to be a synchronization issue with the traffic lights in WOMD and the simulation in Waymax.

Specifically, the traffic lights' states do not always match the agents' states, causing logged agents to cross red lights. Additionally, agents seem to decelerate at green lights, possibly due to a misinterpreted orange light in the real data.

I have written a script to detect these issues, and while it does produce some false positives, the problem occurs in approximately 10% of scenarios in WOMD v1.1 and v1.2.

scenario_15.mp4

scenario_38.mp4

scenario_16.mp4

scenario_63.mp4

[jlambert-waymo]

Thank you @vcharraut, we are reviewing this issue and will have an update soon.

[Abhishek21g]

Opened a fix PR: #93

Approach: When traffic_light_state/all/timestamp_micros diverges from the SDC agent timeline, resample TL states onto the agent clock (offset search + nearest-timestamp fallback) during simulator_state_from_womd_dict.

Includes unit tests and tools/validate_traffic_lights.py for batch scanning. Known repro from waymo-open-dataset#853: training_tfexample.tfrecord-00008-of-01000, scenario index 4.