Table 1: The level of service classified by for fixed-route bus service.

LOS Comments

A 0.00–0.21 1% Service provided like clockwork
B 0.22–0.30 10% Vehicle slightly off headway
C 0.31–0.39 20% Vehicle often off headway
D 0.40–0.52 33% Irregular headways, with some bunching
E 0.53–0.74 50% Frequent bunching
F 0.75 50% Most vehicle bunched

Note: (a) The probability means that a given transit vehicle’s headway will be off headway by more than one-half the scheduled headway .
(b) Applies to routes with headways of 10 minutes or less.
Source: transit capacity and quality of service manual-2nd edition.