This is the song he is singing, me thinks.

Highway Song
Buddy Tabor, Juneau, Alaska

I had a girl up in Denver. She had the key to my heart
But that highway called to me. Lord, it tore us apart
I guess she's still up in Denver. Never seen her again
'Cause when you're out on this highway you're just like the wind

Roll on, roll on. Sing a highway song
Here one day and the next day you're gone
And you roll and you ramble like a leaf in the wind
You pack up your suitcase. You're gone again.

This old highway's like morphine, it can kill all your pain
That dirty old asphalt, it runs through your vein
Like a gambler with his cards or a drunkard his wine
The wheels spin around and you burn up your time

I've been through your towns where they don't know your name
And after awhile they all look the same
I ain't got no friends and I ain't got no home
'Cause when you're out on this highway you're out here alone

That broken white line, it runs through my soul
And I'll follow its path 'til the day I grow old
And the day I grow old I'll lie down by this road
I'll lay down my burdens, I'll lay down my load