context: The Richmond area also has two railroad stations served by Amtrak. Each station receives regular service from north of Richmond including Washington, D.C., Philadelphia, and New York. The suburban Staples Mill Road Station is located on a major north-south freight line and receives all service to and from all points south including, Raleigh, Durham, Savannah, Newport News, Williamsburg and Florida. Richmond's only railway station located within the city limits, the historic Main Street Station, was renovated in 2004. As of 2010, the station only receives trains headed to and from Newport News and Williamsburg due to track layout. As a result, the Staples Mill Road station receives more trains and serves more passengers overall.
question: ప్రధాన వీధి స్టేషను న్యూపోర్ట్ న్యూస్, విలియమ్స్ బర్గ్ నుండి మాత్రమే రైలు ట్రాఫిక్ ఎందుకు అందుతుంది?
answers: track layout