According to the following website, there is a shuttle from the train station, and it comes every 30 minutes going to central Tarquina. They call it an "easy walk" from central Tarquina to the Museo Nazionale and the Monterozzi necropolis, but then say that it's hilly and 4 kilometers (2.49 mi). http://tinyurl.com/dscxz

Best, Sandy in Illinois