Complex sentence: Traveling north, US 17 joins up with US 50 in Paris, Virginia, and the northern terminus of US 17 is in downtown Winchester, Virginia, where the portion of US 50 called the Northwestern Turnpike begins.
Split into simpler sentences: Traveling north, US 17 joins up with US 50 in Paris, Virginia, and the northern terminus of US 17 is in downtown Winchester, Virginia. This is also the point at which the portion of US 50 called the Northwestern Turnpike begins.