A working public transportation system is always a welcome asset in any city. It helps dwellers move around cheaply and with ease while at the time making it a suitable destination for visitors. For a public transportation system to be considered efficient, it needs to tick several important boxes.
A good system develops a clear schedule and makes it known to its (potential) users. The means should show up at the specified time and on the specified route. In the event of emergencies that may cause delays, there should be timely communication, and if possible, a replacement.
The whole point of a public transportation system is to take the burden of commuting off the shoulders of its users. Part of this should be a slash of the cost that they incur when moving from one point to another.
A system needs to have parts that work together as one whole. A train station should, for instance, be served by a working system of buses so that commuters can seamlessly connect between parts. There should also be a way to get one ticket that covers an entire journey between various elements.