Stop Line

Role

This module plans the vehicle’s velocity to ensure it stops just before stop lines and can resume movement after stopping.

Activation Timing

This module is activated when there is a stop line in a target lane.

Module Parameters

Inner-workings / Algorithms

• Gets a stop line from map information.
• Inserts a stop point on the path from the stop line defined in the map and the ego vehicle length.
• Sets velocities of the path after the stop point to 0[m/s].
• Releases the inserted stop velocity when the vehicle halts at the stop point for stop_duration_sec seconds.

Flowchart

@startuml
title modifyPathVelocity
start

:find collision between path and stop_line;

if (collision is found?) then (yes)
else (no)
  stop
endif

:find offset segment;

:calculate stop pose;

:calculate distance to stop line;

if (state is APPROACH) then (yes)
  :set stop velocity;

  if (vehicle is within hold_stop_margin_distance?) then (yes)
    if (vehicle is stopped?) then (yes)
      :change state to STOPPED;
    endif
  endif
else if (state is STOPPED) then (yes)
  if (stopping time is longer than stop_duration_sec ?) then (yes)
    :change state to START;
  endif
else if (state is START) then (yes)
  if ([optional] far from stop line?) then (yes)
    :change state to APPROACH;
  endif
endif

stop
@enduml

This algorithm is based on segment. segment consists of two node points. It’s useful for removing boundary conditions because if segment(i) exists we can assume node(i) and node(i+1) exist.

First, this algorithm finds a collision between reference path and stop line. Then, we can get collision segment and collision point.

Next, based on collision point, it finds offset segment by iterating backward points up to a specific offset length. The offset length is stop_margin(parameter) + base_link to front(to adjust head pose to stop line). Then, we can get offset segment and offset from segment start.

After that, we can calculate an offset point from offset segment and offset. This will be stop_pose.

Restart Prevention

If the vehicle requires X meters (e.g. 0.5 meters) to stop once it starts moving due to poor vehicle control performance, it may overshoot the stopping position, which must be strictly observed. This happens when the vehicle begins to move in order to approach a nearby stop point (e.g. 0.3 meters away).

This module includes the parameter hold_stop_margin_distance to prevent redundant restarts in such a situation. If the vehicle is stopped within hold_stop_margin_distance meters of the stop point (_front_to_stop_line < hold_stop_margin_distance), the module determines that the vehicle has already stopped at the stop point and will maintain the current stopping position, even if the vehicle has come to a stop due to other factors.

Changelog for package autoware_behavior_velocity_stop_line_module

1.0.0 (2025-03-31)

• chore: update version in package.xml
• feat: port autoware_behavior_velocity_planner from autoware.universe to autoware.core (#230) Co-authored-by: Yutaka Kondo <<yutaka.kondo@youtalk.jp>> Co-authored-by: 心刚 <<90366790+liuXinGangChina@users.noreply.github.com>>
• Contributors: Ryohsuke Mitsudome, storrrrrrrrm