No Drivable Lane

Role

This module plans the velocity of the related part of the path in case there is a no drivable lane referring to it.

A no drivable lane is a lanelet or more that are out of operation design domain (ODD), i.e., the vehicle must not drive autonomously in this lanelet.
A lanelet can be no drivable (out of ODD) due to many reasons, either technical limitations of the SW and/or HW, business requirements, safety considerations, .... etc, or even a combination of those.

Some examples of No Drivable Lanes

• Closed road intentionally, due to construction work for example
• Underpass road that goes under a railway, for safety reasons
• Road with slope/inclination that the vehicle is not be able to drive autonomously due to technical limitations. And lots of other examples.

A lanelet becomes invalid by adding a new tag under the relevant lanelet in the map file <tag k="no_drivable_lane" v="yes"/>.

The target of this module is to stop the vehicle before entering the no drivable lane (with configurable stop margin) or keep the vehicle stationary if autonomous mode started inside a no drivable lane. Then ask the human driver to take the responsibility of the driving task (Takeover Request / Request to Intervene)

Activation Timing

This function is activated when the lane id of the target path has an no drivable lane label (i.e. the no_drivable_lane attribute is yes).

Module Parameters

Parameter	Type	Description
stop_margin	double	[m] margin for ego vehicle to stop before speed_bump
print_debug_info	bool	whether debug info will be printed or not

Inner-workings / Algorithms

• Get no_drivable_lane attribute on the path from lanelet2 map
• The no drivable lane state machine starts in INIT state
• Get the intersection points between path and no drivable lane polygon
• Assign the state to APPROACHING toward a no drivable lane if:
  • the distance from front of the ego vehicle till the first intersection point between the ego path and the no drivable lane polygon is more than the stop_margin
• Assign the state to INSIDE_NO_DRIVABLE_LANE if:
  • the first point of the ego path is inside the no drivable lane polygon, or
  • the distance from front of the ego vehicle till the first intersection point between the ego path and the no drivable lane polygon is less than the stop_margin
• Assign the state to STOPPED when the vehicle is completely stopped

Future Work

• As Request to Intervene API is not implemented yet, this will be handled to notify the driver to takeover the driving task responsibility after the vehicle stops due to no_drivable_lane
• Handle the case when the vehicle stops before a no drivable lane but part of its footprint intersects with the no drivable lane polygon.