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R32 / 1c:Mc-1

Road Map Specification identifies zero, one or many Road

Road is identified by zero or one Road Map Specification

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A perceived Road may or may not be found on a map (identified by the mapping system) at a given point in time. If it is correlated, it must be with a single map designation. In case of doubt, there is no correlation.

It stands to reason that a Road Map Specification would name a single Road. But how could the same specification name multiple Roads?

Imagine the case when an exit diverges just up ahead of the Ego Vehicle, forming its own separate Road. Now let’s say that the exit leads to a continuation of the same Road Map Specification.

Let’s say, for example, that we are on SR-1 (California Highway 1) which merges onto I280 (Interstate 280), but the exit will keep us on HWY1. So now we have two perceived Roads (HWY1) which we are driving on, and HWY1 corresponding to the exit Road. (I280 is not yet detected, but will become the new designation of the current Road if we don’t take the exit).

Comment: This all depends on how we defined Road transitions. In the above example, the Road we are on is continuous before and past the exit. So, as we drive past the exit, our Road is re-associated with a new Road Map Specification (from SR-1 to I280). The exit is a new Road (right and left edges) and is associated with SR-1. But, just before the exit, both Roads are associated with SR-1.

But let’s say that we decide to model this another way. Maybe we break our Road into Road Segments before and after the exit. Well, that still doesn’t help since they would presumably belong to the same Road. Or, we might say that the exit is not really SR-1. Perhaps an exit should have its own name such as 508A. In that case. We’re going to have to do a thorough analysis of freeway interchanges before we’re sure. For now, we’ll leave this as a 0..1:1..* association pending further development of the model.

Formalization

Known Map Road.Road -> Road.ID
Known Map Road.(Map name, Territory, Country) ->
    Road Map Specification. (Map name, Territory, Country)