Final Report - Pima Association of Governments

High Capacity Transit System Plan - Final Report June 2009
Appendix A
Table A-2 On-Time Performance QOS
QOS On-Time Percentage Comments*
A 95.0-100.0% No more than 1 late transit vehicle every 2 weeks
B 90.0-94.9% 1 late transit vehicle every week
C 85.0-89.9% 3 late transit vehicles every 2 weeks
D 80.0-84.9% 2 late transit vehicles every week
E 75.0-79.9% 1 late transit vehicle every day
F 0.75 Most vehicles bunched
NOTE: This table differs from the corresponding table in the TCQSM.
On‐Time Performance QOS reflects predictability: whether or not vehicles arrive at the scheduled
time or within an acceptable window of time around the scheduled time (e.g., no more than five
minutes after the scheduled time). On‐Time Performance QOS is calculated as the percentage of
arrivals that are “on time” within a certain span of time. The TCQSM suggests that the span is a
minimum of 20 observations at a given stop. On‐time performance data can be obtained using
automatic vehicle location (AVL) data or by manual ride‐checks.
Headway Adherence QOS reflects the coefficient of variation of headways. The coefficient of
variation of headways represents the regularity of headways. It is calculated as follows:
coefficient of variation
of headways
=
standard deviation of headway deviations
average scheduled headway
In the above equation, headway deviation is the difference between the scheduled headway and
the actual headway.
A-3