Add safety slow down feature for specific crosswalks

[mehmetdogru]

With the current implementation of crosswalk module, ego vehicle doesn't slow down for crosswalks unless there are target objects around it. However for some use cases as stated below slowing down for some crosswalks where there are no traffic lights either for pedestrians or vehicles, makes sense:

• Streets near school exists or campus areas where extra precaution needs to be taken since unpredictable and sudden pedestrian behaviors can be observed

• Narrow roads and occluded perception output ( Even though there is occlusion_spot module in behavior_velocity_planner, I guess it is still experimental)

So an implementation which would affect only user-selected crosswalk's behavior can be done by adding some tags in crosswalk annotation in lanelet2_map and making necessary changes in crosswalk module:

<relation id='34378' visible='true' version='1'>
    <member type='way' ref='34374' role='left' />
    <member type='way' ref='34377' role='right' />
    <tag k='subtype' v='crosswalk' />
    <tag k='safety_slow_down_speed' v='3.0' />
    <tag k='safety_slow_down_distance' v='2.0' />
    <tag k='type' v='lanelet' />
</relation>

safety_slow_down_speed in [m/s]
safety_slow_down_distance in [m]

Please feel free to give ideas about the implementation.

Related issue: autowarefoundation/autoware.universe#1523

[TakaHoribe]

@satoshi-ota FYI. Any comments?

[VRichardJP]

If I understand your idea, you want the vehicle to slow down when it gets close to some specific crosswalk. But wouldn't it be simpler to just reduce the max speed on the road lanelet instead?

[mehmetdogru]

@VRichardJP

Thank you for the input. Of course it would be for me; however not for the user. In such a case user would have to cut the lane before and after the crosswalk (create a separate lanelet) then modify the speed of the lanelet. And to make these changes on existing lanelet2_maps is also very time consuming.

Also that kind of changes usually are not wanted since they don't have any semantic meaning. The ego vehicle is not slowing down because max speed limit is lower than the other lanes, it is slowing down to take extra precaution for the crosswalk and the decision of slowing down is autoware's to make. What I am trying to say is that I think max speed limits on lanelets should be used only to specify the legal speed limits decided by regulations (eg. speed limit traffic sign) or if it is a matter of the whole road all the way (eg. bumpy road structure). But crosswalk is not about the road itself it is a separate unit.

[VRichardJP]

I get the point. Maybe it would make sense to add a safety_slow_down_distance parameter aswell? (in a similar fashion than slow_margin and slow_velocity work in scene_crosswalk.cpp)

For example, if we imagine a situation where a pedestrian may be hidden by a wall, the safety_slow_down_distance could be adjusted so that the safety_slow_down_speed is reached at the location from where the vehicle can finally see behind the wall. The safety_slow_down_speed would be maintained until the crosswalk has been passed.

[mehmetdogru]

Yes actually adding an extra tag as safety_slow_down_distance makes sense. Thank you!

[mehmetdogru]

Related issue: autowarefoundation/autoware.universe#1523