Which is the best way to visualize effectively a train timetable? Well probably there is a lot of ways to visualize this kind of data, and one of them is using the stem-and-leaf plot (called also stemplot). Using this technique the amount of data to display (hours and minutes) can be reduced.

Why are the stem-and-leaf plots useful in that case? This kind of plot is a method for showing the frequency with which certain classes of values occur. You could achieve the same by making a frequency distribution table or a histogram for the values, or you can use a stem-and-leaf plot and let the numbers themselves to show pretty much the same information.