Complex sentence: I-10 is the fourth longest Interstate Highway in the United States, following I-90, I-80, and I-40, with about of its length within the state of Texas, where the freeway spans the state at its widest breadth.
Split into simpler sentences: I-10 is the fourth longest Interstate Highway in the United States, following I-90, I-80, and I-40. About one-third of its length within the state of Texas, where the freeway spans the state at its widest breadth.