Another analogy might be the NYC subway, where in Manhattan you have lines like 1/2/3, A/C/E, B/D/F/M, N/R/W etc. that share a number of stops in southern Manha

Another analogy might be the NYC subway, where in Manhattan you have lines like 1/2/3, A/C/E, B/D/F/M, N/R/W etc. that share a number of stops in southern Manhattan, so along the 1/2/3 or A/C/E, the sum of tph matters... but as they break from that "trunk" in the boroughs, or at the ends of Manhattan, the individual lines matters.