Métro
Inner Working

A few notes on Métro 's inner working to help you understand its current limitations:

To compute the best route, the program uses an estimate of the time needed to run each route. But to avoid filling the memory with too much data (the timetables), the times used are quite simplified.

There are only a limited range of possibilities: for example, one average time for a travel between 2 stations on a subway and one average time between 2 stations on an express or streetcar line. In Paris, the times used are 1'30 for the first (subways) and 3' for the second (RER and streetcars).

For the connections, it's just about the same: one time for a "standard" connection and one average time for a "long" connection (between 2 different stations or to an express line, to account for the longer wait). Again for Paris, values are 4' and 8'.

This method, though quite efficient most of the time, brings its limitations (but I'm working on some of them): travel times on express lines are computed with all the intermediate stations (express lines not being yet known to the program) leading to over-estimation; the soft does not always make a difference if a line is more frequent than another, so that it may suggest a low-frequency line when there is a better one for the same route.

This last point is what makes Métro less adequate for streetcars, railroads or buses (these having other peculiarities making them difficult to use in Métro).

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