Nice visual presentation can be achieved by drawing the street map line layer twice, i.e., have the same layer two times in the project, one layer on top of the other. First draw the full width lines representing each road or street in the lower layer. Then render the same lines more narrowly in a different color in the upper layer, so that each narrow-rendered line partially hides the wider version of the same street line in the layer below. When the two layers are presented together, the result is that the upper layer forms the line interiors while the still visible edge portions of the wider lines in the layer below form the line outlines.
The alternative is to just use the line outline feature within the visual layer property control, though the two-layer method described above can deliver a nicer visual presentation.