As a Michigander, I'd say "Take US131" or "Get on I96 eastbound to M44", just in the same way I'd say "Take a right on Main Street". The United States Highway/

As a Michigander, I'd say "Take US131" or "Get on I96 eastbound to M44", just in the same way I'd say "Take a right on Main Street". The United States Highway/Interstate/Michigan abbreviations are pretty common, but optional. And come to think of it, that's exactly how Waze and Google Maps and Apple Maps turn-by-turn directions read to me. Do these programs use different dialects in Southern California? I would use the definite article with a route on a transit system, though, for example to identify a bus line or (when in a city that has one) a subway: "I'll ride the 28 home" or "I commute on the 10".