Complex sentence: US 15's last intersection in Maryland is with the northern end of US 15 Business (Seton Avenue) and Welty Road, which leads to Old Gettysburg Road; there is no direct access from northbound US 15 Business to northbound US 15.
Split into simpler sentences: US 15's last intersection in Maryland is with the northern end of US 15 Business (Seton Avenue) and Welty Road, which leads to Old Gettysburg Road. There is no direct access from northbound US 15 Business to northbound US 15.