en travers versus à travers

[alan gould]

I looked at examples of these two perhaps too briefly.  The former is defined as "across" and the latter as "through" but it's not clear.  If there isn't a pattern, it would at least be helpful to know which is used more often and I'll use that when I'm unsure.

merci d'avance  

[Vedas]

Hello,

en travers has an idea of an obstacle like something blocking a railway track for instance: une voiture en travers de la voie

à travers means to cross something, to walk across/ through/ like marcher à travers  champs/ bois