Katunan kariya na waje sune ginshiƙai na kariya waɗanda aka tsara don kare muhimman kayayyakin more rayuwa, kamar kabad na lantarki, mitar ruwa, layukan iskar gas, da kayan aikin sadarwa. Suna samar da shinge mai ƙarfi na zahiri daga tasirin haɗari da ɓarna a cikin ababen hawa yayin da suke kiyaye isa ga masu gyara.
