Secondary Routes will begin with a number, and end in a letter. The rationale of this is to identify where the route is centralized with, and where it is going. It also identifies that this route does not serve Downtown. Obviously, the numbers will have to make sense. Let’s consider Aspinwall for example which is given the number 15.
Therefore, one might see the 15U: Highland Avenue. The 15 identifies that it connects with Aspinwall, and the U in this case identifies it goes to Oakland. Another example will be the 21E: Bakery Sq. which shows Manchester/Allegheny West (number 21), and goes to the East (Bakery Sq.).
Each letter is based on the directions (E, N, S, W), and a major destination (U for University of Pittsburgh). U will also be chosen to not confuse the number 0 (zero) or O (Oakland). U will not have any primary routes. Last, the letters R (Rush Hour Service), and L (Late Night) can operate in secondary route fashions, but less likely.