This particular phrase, turn into, is an idiom which means "to become."
...When he drinks, he turns into a monster.
So with the word turn, unless the meaning is "to become," in to has to be two words.
...He turned in to the driveway.
...He turned in to the roadway.
But
...He pulled into the driveway.
...He pulled into the roadway.
Happy punctuating!
Margie