Each map is based on the situation at the end of the year in question. Transit services are shown only if they were frequent (running at least every 20 minutes during the mid-day off-peak period on weekdays) and included significant segments of grade-separated right of way with stops at least every 1.5 to 3 km. Through-running in streets or street medians where the transit vehicles did not have absolute priority at intersections is shown with thinner lines. (Services that ran entirely on the surface with no grade-separated sections are not shown.)