Decrease rendering for railways without a route=train relation

[kolgza]

Description

Much of the existing rail infrastructure throughout North America only serves freight. They cannot be used by individual travelers, and so information about them is only useful to a select few. Additionally, rendering freight-only railways as prominently as passenger railways adds noise and ambiguity.

A solution to this problem would be to consider the presence of a route=train relation when rendering railways.

Links and screenshots illustrating the problem

Pittsburgh:


Philadelphia:

[imagico]

Will depend on #4112.

Note however that the observation made here (that railway tracks without a regular public passenger service are rendered too prominently/too early) is not universally the case, in particular in non-urban areas.

Also it seems that route=train is not universally used for public passenger service routes only.