street_density_km = None
// average circuity: sum of edge lengths divided by sum of great circle distance between edge endpoints
points = [((G.node[u]["y"], G.node[u]["x"]), (G.node[v]["y"], G.node[v]["x"])) for u, v in G.edges()]
great_circle_distances = [great_circle(p1, p2).m for p1, p2 in points]
try:
circuity_avg = edge_length_total / sum(great_circle_distances)
except ZeroDivisionError: