Can I modify the Roads Layer under Reference to include all major and minor roads including side streets, neighborhood streets and major thoroughfares?
A national roads layer of that detail would be several gigabytes at least and it will not be efficient to the majority of users. We compromise by offering a major roads layer and minor roads-by-county layers. Minor roads can be added for each county in the US using the Add Layer button on the map toolbar, then click the “Roads” category.