carla-simulator/carla-agentic-tools/control-traffic-lights

Control traffic lights

Paths. scripts/… and references/… below are relative to the

directory holding this SKILL.md. Your working directory is the user's

project, not that directory, so prefix them with its absolute path or the

command is not found.

Drive the actual traffic.traffic_light actors: set states, freeze them, tune phase timing. Not to be confused with `control-traffic` — that is the Traffic Manager governing how autopilot vehicles drive; this is the lights themselves.

Instructions

Progress:
- [ ] Step 1: Check prerequisites (bash scripts/check_env.sh), clear FAILs
- [ ] Step 2: list to see lights/states; get a junction id from map-waypoints if needed
- [ ] Step 3: set / freeze / timing / reset (all, by id, by junction, or nearest)

Commands need CARLA_HOST/CARLA_PORT from scripts/env.sh. Negative coordinates: use --near=-24,-57,1.

Step 1: Check prerequisites

bash scripts/check_env.sh

Step 3: Control

source scripts/env.sh
 
python3 scripts/traffic_lights.py list                      # ids, states, timing
 
# freeze the whole grid green (classic "green wave" / free-flow test)
python3 scripts/traffic_lights.py freeze on --state green
python3 scripts/traffic_lights.py freeze off                # back to normal cycling
 
# set one light, or all in a junction, or the nearest to a point
python3 scripts/traffic_lights.py set --state red --id 42
python3 scripts/traffic_lights.py set --state green --junction 838
python3 scripts/traffic_lights.py set --state red --near=-24,-57,1
 
# phase timing (seconds) on all lights
python3 scripts/traffic_lights.py timing --green 20 --yellow 3 --red 10 --all
 
python3 scripts/traffic_lights.py reset                     # normal cycle again

Examples

Example 1: let traffic flow

User says: "make all the lights green so cars don't stop"

freeze on --state green. All lights hold green until freeze off / reset.

Example 2: red light at one junction

User says: "make the crossroads in the middle red"

map-waypoints junctions --arms 4 → central junction id → set --state red --junction <id>.

Example 3: faster cycle

User says: "shorten the light cycle"

timing --green 10 --yellow 2 --red 6 --all.

Troubleshooting

Problem: lights snap back after `set` Cause: they keep cycling; set changes the current state, the cycle continues. Solution: freeze on to hold a state, or timing to change the cycle itself.

Problem: `--junction` returns nothing Cause: wrong junction id, or that junction has no signalised lights. Solution: get the id from map-waypoints junctions; not all junctions are lit.

Problem: vehicles still stop at a green I set Cause: they may be on a different phase, or autopilot reacts to its own light. Solution: freeze on --state green affects all; or let cars ignore lights via control-traffic (ignore-lights).

Outputs

Traffic-light state on the server (states/freeze/timing). No file. list reports current states and timings.

Detail (states, freeze semantics, groups, per-junction/waypoint lookup) in references/traffic-lights.md.