Implementation:CARLA simulator Carla ConstantVelocityAgent

Knowledge Sources	CARLA
Domains	Agent Navigation, Autonomous Driving
Last Updated	2026-02-15 05:00 GMT

Overview

A Python agent that navigates the CARLA scene at a fixed velocity, extending BasicAgent with constant velocity physics and collision-responsive behavior.

Description

The ConstantVelocityAgent class extends BasicAgent to drive a vehicle at a constant speed using CARLA's enable_constant_velocity physics mode. The agent converts the target speed from km/h to m/s and applies it as a forward velocity vector. It sets up a collision sensor that automatically stops the constant velocity on impact. After a configurable restart_time, the agent resumes constant velocity driving. During each run_step(), the agent checks for vehicle obstacles (using _vehicle_obstacle_detected) and red traffic lights (using _affected_by_traffic_light). When a hazard is detected, the constant velocity is temporarily reduced to the hazard speed (or zero for traffic lights). The optional use_basic_behavior flag allows falling back to BasicAgent steering logic when the constant velocity is stopped. Key methods include set_target_speed(speed), stop_constant_velocity(), restart_constant_velocity(), and destroy_sensor().

Usage

Use this agent for scenarios requiring a vehicle to maintain a steady cruising speed while still reacting to traffic lights and other vehicles. It is suitable for highway-like driving or testing constant-speed behavior.

Code Reference

Source Location

• Repository: CARLA
• File: PythonAPI/carla/agents/navigation/constant_velocity_agent.py

Signature

class ConstantVelocityAgent(BasicAgent):
    def __init__(self, vehicle, target_speed=20, opt_dict={}, map_inst=None, grp_inst=None)
    def set_target_speed(self, speed)
    def stop_constant_velocity(self)
    def restart_constant_velocity(self)
    def run_step(self)
    def destroy_sensor(self)

Import

from agents.navigation.constant_velocity_agent import ConstantVelocityAgent

I/O Contract

Inputs

Name	Type	Required	Description
vehicle	carla.Vehicle	Yes	Vehicle actor to control
target_speed	float	No	Target speed in km/h (default: 20)
opt_dict	dict	No	Options: restart_time (float), use_basic_behavior (bool)
map_inst	carla.Map	No	Pre-loaded map instance to avoid expensive calls
grp_inst	GlobalRoutePlanner	No	Pre-loaded route planner instance

Outputs

Name	Type	Description
control	carla.VehicleControl	Steering and throttle control for the current step

Usage Examples

import carla
from agents.navigation.constant_velocity_agent import ConstantVelocityAgent

client = carla.Client('localhost', 2000)
world = client.get_world()

# Spawn a vehicle
bp = world.get_blueprint_library().find('vehicle.tesla.model3')
spawn_point = world.get_map().get_spawn_points()[0]
vehicle = world.spawn_actor(bp, spawn_point)

# Create agent with 30 km/h target
agent = ConstantVelocityAgent(vehicle, target_speed=30, opt_dict={'restart_time': 5.0})

# Set a destination
destination = world.get_map().get_spawn_points()[10].location
agent.set_destination(destination)

# Simulation loop
while True:
    if agent.done():
        break
    control = agent.run_step()
    vehicle.apply_control(control)

# Cleanup
agent.destroy_sensor()
vehicle.destroy()

Related Pages

• Environment:CARLA_simulator_Carla_Python_API_Runtime