As I understand GMRS is becoming more common on the interstates, can't say for sure, don't have a mobile radio in my truck. Although there is no official highway common for traveling the highways and by-ways, per the video at: "What Is The Official GMRS Road, Tr...ghway Use", Channel 19 with no tone is the (not) official designated channel for traveling
Ch.19 was the CB road channel, stay consistent. Yes, the guy in the video refers to the issue of using Ch.19 near the Canadian border (line "A") but until we get a national consensus on something else -- his reasoning regarding Ch.19 sounds good to me. If I ever put a radio in my truck I will actually care.

BTW, Ch.16 is apparently the designated off-road common channel. That's also mentioned in the video.