Simplify the following text for a Grade 7 native English-speaking person.
Original: Major northâ `` south routes have numbers ending in `` 1 '' while major eastâ `` west routes have numbers ending in `` 0 '' .
Simplified: The important east\/west U.S. Highways usually have numbers ending in `` 0 '' and the important north\/south Interstates have numbers ending in `` 1 '' . Many of the routes ending in `` 0 '' or `` 1 '' used to go across the country , but no longer do because of the Interstate Highway System .