Intersection Collision Checker

The intersection_collision_checker is a plugin module of autoware_planning_validator node. It is responsible for validating the planning trajectory at intersections by verifying that it does NOT lead to a collision with other road vehicles.

The check is executed only when:

• Ego is approaching a turn_direction lane
• Ego trajectory intersects with lanes other than route_lanelets

Inner workings

The following steps describe the general approach taken to check for collisions at intersections:

• Compute ego trajectory lanelets and turning direction
• Compute target lanelets to check
• For each target lanelet set the point_of_overlap (i.e where ego trajectory intersects the lanelet), and compute ego's time to reach it.
• Filter obstacle pointclouds to remove unwanted points
• For each target lanelet:
  • process pointcloud points within lanelet and measure distance to point_of_overlap
  • estimate object velocity based on changes in distance measurements
  • estimate object's time to reach point_of_overlap
  • compare object's and ego's time to reach to determine if there is a risk of collision.

If it's determined that there is a risk of collision, a diagnostic is published to trigger an emergency stop by the MRM Handler.

Target Lanelet Selection

Right turn

To get the target lanelets, we first find all lanelets intersecting with ego trajectory. Then we filter out:

• Lanelets that are route_lanelets
• Lanelets with a "time to reach" exceeding the time horizon
• Lanelets that have turn_direction attribute and are not STRAIGHT. (If parameter right_turn.check_turning_lanes is FALSE)
• Lanelets that are determined to be crossing lanes. (If parameter right_turn.check_crossing_lanes is FALSE)

Target lanelets are then expanded, if necessary, up to detection_range

The image below shows the target lanelets at a right turn intersection. (right_turn.check_turning_lanes set to FALSE)

Left turn

To get the target lanelets in case of a left turn:

• First we find the turn_direction lanelet from the Ego trajectory lanelets
• Then we find the next lanelet "destination_lanelet" following the turn_direction lanelet
• We then get all lanelets preceding the "destination_lanelet" and filter out:
  • Lanelets that are route_lanelets
  • Lanelets with a "time to reach" exceeding the time horizon
  • Lanelets that have turn_direction attribute and are not STRAIGHT. (If parameter left_turn.check_turning_lanes is FALSE)

Target lanelets are then expanded, if necessary, up to detection_range

The image below shows the target lanelets at a left turn intersection. (left.check_turning_lanes set to TRUE)

Parameters

Name	Unit	Type	Description	Default value
enable	[-]	bool	Flag to enable/disable the check globally	true
detection_range	[m]	double	Range of detection from ego position, pointcloud points beyond this range are filtered out	50.0
ttc_threshold	[s]	double	Threshold value for the difference between ego and object reach times to trigger and a stop	1.0
ego_deceleration	[m/ss]	double	Ego deceleration relate used to estimate ego stopping time	1.0
min_time_horizon	[s]	double	Minimum time horizon to check ahead along ego trajectory	10.0
on_time_buffer	[s]	double	Continuous collision detection time required to judge as unsafe	0.5
off_time_buffer	[s]	double	Continuous no collision detection time required to clear unsafe decision	1.0

Lanelet Selection Flags

Name	Unit	Type	Description	Default value
right_turn.enable	[-]	bool	Flag to enable/disable the check at right turns	true
right_turn.check_crossing_lanes	[-]	bool	Flag to enable/disable checking crossing lanes	true
right_turn.check_turn_lanes	[-]	bool	Flag to enable/disable checking turning lanes	true
right_turn.crossing_lane_angle_th	[rad]	double	Angle threshold for determining crossing lanes	0.785398
left_turn.enable	[-]	bool	Flag to enable/disable the check at left turns	true
left_turn.check_turn_lanes	[-]	bool	Flag to enable/disable checking turning lanes	true

Pointcloud Parameters

Name	Unit	Type	Description	Default value
pointcloud.height_buffer	[m]	double	Height offset to add above ego vehicle height when filtering pointcloud points	true
pointcloud.min_height	[m]	double	Minimum height threshold for filtering pointcloud points	50.0
pointcloud.voxel_grid_filter.x	[m]	double	x value for voxel leaf size	1.0
pointcloud.voxel_grid_filter.y	[m]	double	y value for voxel leaf size	1.0
pointcloud.voxel_grid_filter.z	[m]	double	z value for voxel leaf size	10.0
pointcloud.clustering.tolerance	[m]	double	Distance tolerance between two points in a cluster	1.0
pointcloud.clustering.min_height	[m]	double	Minimum height of a cluster to be considered as a target	1.0
pointcloud.clustering.min_size	[-]	double	Minimum number of points in a cluster to be considered as a target	1.0
pointcloud.clustering.max_size	[-]	double	Maximum number of points in a cluster to be considered as a target	1.0
pointcloud.observation_time	[s]	double	Minimum detection time for a pointcloud object to be considered reliable	1.0
pointcloud.latency	[s]	double	Time delay used to compensate for latency in pointcloud data	1.0