From SimCity Wiki
|function||Supports the movement of Streetcars|
|description||Two tracks for streetcars to travel along, useful for connecting sections of your city that do not share roads.|
Streetcar tracks are particularly useful for connecting streetcars to areas of the city that don't have avenues. Sims are capable of walking to streetcar stops near rail crossings, but usually won't if they are too far from a crossing.