Implementation:CARLA simulator Carla ALSM

Knowledge Sources	CARLA
Domains	Traffic_Management, Autonomous_Driving
Last Updated	2026-02-15 05:00 GMT

Overview

The ALSM (Agent Lifecycle and State Management) class is responsible for updating the local cache of kinematic states and managing the memory and cleanup for a varying number of vehicles in the CARLA traffic manager simulation.

Description

ALSM stands for Agent Lifecycle and State Management and serves as the central bookkeeping component of the Traffic Manager pipeline. It performs the following core responsibilities:

Actor Discovery: Scans the simulation world each tick to identify newly spawned actors (vehicles, pedestrians) that are not yet tracked, and adds them to the unregistered_actors map.
Actor Destruction Detection: Compares the current world actor list against previously known registered and unregistered actors to detect which actors have been destroyed, then invokes RemoveActor to clean up associated data structures across all pipeline stages.
Hero Vehicle Tracking: Maintains a map of actors with the role_name attribute set to "hero", used by hybrid physics mode to determine which vehicles require full physics simulation.
State Updates: Calls UpdateRegisteredActorsData and UpdateUnregisteredActorsData each tick to refresh kinematic state (location, rotation, velocity) and static attributes for all tracked actors in the SimulationState cache.
Idle Vehicle Removal: Tracks how long registered vehicles remain stuck at a single location via IdleTimeMap. If a vehicle exceeds the maximum idle threshold and is not a hero actor, ALSM destroys it to prevent traffic deadlocks.
OSM Mode Cleanup: When Open Street Map mode is active, processes a list of actors marked_for_removal by other pipeline stages and destroys them.

The class holds references to all pipeline stages (LocalizationStage, CollisionStage, TrafficLightStage, MotionPlanStage, VehicleLightStage) so it can propagate actor addition and removal events to each stage.

Usage

ALSM is instantiated and owned by TrafficManagerLocal. It is invoked once per simulation tick via its Update() method before the pipeline stages execute. It should not be instantiated directly by user code; it is an internal component of the Traffic Manager architecture.

Code Reference

Source Location

Repository: CARLA
File: LibCarla/source/carla/trafficmanager/ALSM.cpp
Header: LibCarla/source/carla/trafficmanager/ALSM.h

Signature

class ALSM {
public:
  ALSM(AtomicActorSet &registered_vehicles,
       BufferMap &buffer_map,
       TrackTraffic &track_traffic,
       std::vector<ActorId>& marked_for_removal,
       const Parameters &parameters,
       const cc::World &world,
       const LocalMapPtr &local_map,
       SimulationState &simulation_state,
       LocalizationStage &localization_stage,
       CollisionStage &collision_stage,
       TrafficLightStage &traffic_light_stage,
       MotionPlanStage &motion_plan_stage,
       VehicleLightStage &vehicle_light_stage);

  void Update();
  void RemoveActor(const ActorId actor_id, const bool registered);
};

Import

#include "carla/trafficmanager/ALSM.h"

I/O Contract

Inputs

Name	Type	Required	Description
registered_vehicles	AtomicActorSet&	Yes	Set of vehicles registered with the Traffic Manager
buffer_map	BufferMap&	Yes	Waypoint buffers for all tracked vehicles
track_traffic	TrackTraffic&	Yes	Object tracking overlapping vehicle paths
marked_for_removal	std::vector<ActorId>&	Yes	Actors flagged by pipeline stages for destruction
parameters	const Parameters&	Yes	Traffic Manager configuration parameters
world	const cc::World&	Yes	CARLA world object for querying actors and snapshots
local_map	const LocalMapPtr&	Yes	Shared pointer to the in-memory map cache
simulation_state	SimulationState&	Yes	Mutable cache of actor kinematic and static state
localization_stage	LocalizationStage&	Yes	Reference to the localization pipeline stage
collision_stage	CollisionStage&	Yes	Reference to the collision avoidance pipeline stage
traffic_light_stage	TrafficLightStage&	Yes	Reference to the traffic light response stage
motion_plan_stage	MotionPlanStage&	Yes	Reference to the motion planning pipeline stage
vehicle_light_stage	VehicleLightStage&	Yes	Reference to the vehicle light management stage

Outputs

Name	Type	Description
simulation_state	SimulationState&	Updated kinematic state cache for all actors (modified in place)
buffer_map	BufferMap&	Cleaned up waypoint buffers with destroyed actors removed
registered_vehicles	AtomicActorSet&	Updated set with destroyed registered actors removed

Usage Examples

// ALSM is created and used internally by TrafficManagerLocal.
// During construction of TrafficManagerLocal:
alsm(ALSM(registered_vehicles,
          buffer_map,
          track_traffic,
          marked_for_removal,
          parameters,
          world,
          local_map,
          simulation_state,
          localization_stage,
          collision_stage,
          traffic_light_stage,
          motion_plan_stage,
          vehicle_light_stage));

// Called once per tick in the TrafficManagerLocal::Run() loop:
alsm.Update();

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Principle

Implementation

Heuristic

Environment