Design of Intersection API

Another relevant aspect when making use of map data for automated driving is priority handling within intersections. Therefore, ad_map_access provides special functionality to cope with intersections. Since the priority handling within an intersection is tightly coupled with the route a vehicle drives through the intersection, a route (or parts of it) are used as basis for the creation of an intersection::Intersection() class.

A call of the static function intersection::Intersection::getIntersectionsForRoute(route::FullRoute) in the below sketched example, returns a list with three intersection::Intersection objects.

Visualization of a route with three intersections on the way

Priority rules within intersection

The intersection object internally calculates the priority rules for lanes of the intersection:

• What are the lanes of the intersection - internal intersection lanes (with higher prio, with lower prio) - lanes outside the intersection entering (incoming) or leaving (outgoing) intersection - lanes of the ego-route through the intersection
• What are the (relevant) traffic lights on the ego-route through the intersection?
• What is the turn direction of the ego-route through the intersection?

Object checks for the intersection

The intersection::Intersection object provides checks for objects and their relation in respect to the intersection like is an object...

• within the intersection
• on a crossing lane
• on a lane with higher/lower prio
• on an internal or incoming lane (with higher prio, with lower prio)
• on a route crossing the ego route through the intersection on lanes with higher prio
• on a route from the same intersection arm
• on a route from the exactly opposite direction through the intersection

These checks build the basis for maneuver planning at intersection level.

Supported intersection types

For sure, the current implementation does not support any intersection configuration thinkable, but it builds a basis and should work for common types of intersection in right-handed traffic as well as in left-handed traffic:

• HasWay
• Stop
• Yield
• AllWayStop regulation (U.S.A.)
• Traffic Light regulated intersections
• Crosswalk (which is treated as a special kind of intersection)
• PriorityToRight
• PriorityToRightAndStraight (Singapore)