Also from the PTC website:
# Route should be direct and
avoid circuitous routings. Route should not be more than 30%
longer in distance than comparative trips by car. Generally, there
should be no more than 2 branches per trunk route.
Services 3, 8, 14, 28, 38, 51, 61, 74, 112, 113,
123, 143, 166, 800, 811, 812 etc.
