Post on 01-Jan-2016
description
Bus Service ReliabilityDeveloping new performance
measures
Unreliability Vs. Bus Bunching
Meead Saberi K.
meead@pdx.edu
Bus Trip AutopsyBus Trip AutopsyUnreliability sourcesUnreliability sources
Bus closes Bus closes the door and the door and is ready to is ready to
leaveleave
Bus stops Bus stops and opens and opens the doorthe door
Bus Bus leavesleaves
Non-stop tripNon-stop tripNon-stop tripNon-stop trip
Dwell timeDwell time Clearance timeClearance time
Delay in Delay in ArrivingArriving
Study AreaStudy Area
105 scheduled trips per weekday
64 stops
Scheduled trip times range 40-45 minutes
Scheduled headways range 3-55 minutes
Data: Tuesday, February 1, 2001
Route-Level Trip TimeRoute-Level Trip Time(inbound trip)(inbound trip)
0:20
0:30
0:40
0:50
1:00
1:10
0:00 6:00 12:00 18:00 0:00
Time of Day
Rou
te T
rave
l Tim
e (m
in)
Average trip time = 42:03
Standard deviation = 05:11
Coefficient of Variation = 0.12
90th% - 40th% (Layover) = 08:51
Route-Level Trip TimeRoute-Level Trip Time(outbound trip)(outbound trip)
0:20
0:30
0:40
0:50
1:00
1:10
0:00 6:00 12:00 18:00 0:00
Time of Day
Rou
te T
rave
l Tim
e (m
in)
Average trip time = 45:25
Standard deviation = 07:58
Coefficient of Variation = 0.17
90th% - 40th% (Layover) = 16:31
Current Reliability MeasuresCurrent Reliability MeasuresProposed by HCM and TCQSMProposed by HCM and TCQSM
On-Time PerformanceOn-Time Performance
Headway AdherenceHeadway Adherence
Stop-level Delay = Actual Arrive Time – Scheduled Arrive Time
Stop-level Delay = Actual Headway – Scheduled Headway
Current Reliability MeasuresCurrent Reliability MeasuresProposed by HCM and TCQSMProposed by HCM and TCQSM
On-Time PerformanceOn-Time Performance
Stop-level Delay = Actual Arrive Time – Scheduled Arrive Time
Current Reliability MeasuresCurrent Reliability MeasuresProposed by HCM and TCQSMProposed by HCM and TCQSM
Headway AdherenceHeadway Adherence
Stop-level Delay = Actual Headway – Scheduled Headway
Current Reliability MeasuresCurrent Reliability MeasuresProposed by HCM and TCQSMProposed by HCM and TCQSM
Why current measures, based on coefficient of variation and simply counting the number of late buses, do not tell the whole story?
Based on preliminary analysis of empirical data, delay distribution both in terms of headway for frequent services and scheduled arrival time for not frequent services is often wide and skewed specially when congestion occurs. Large delays cause “bus bunching”, no matter what the delay source is and in which link it occurs.
To find out the possible delay source(s), link level analysis should be done to find the “problem causing” link in terms of variation in travel time. A stop level analysis should also be done to measure reliability.
New Reliability New Reliability MeasureMeasure
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
0 100 200 300 400
Delay (sec)
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-400 -300 -200 -100 0
Delay (sec)
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-200 -100 0 100 200
Delay (sec)
Which distribution is ideal from the perspective of a passenger?
%100 Early%100 Early %100 Late%100 Late%50 Early & %50 %50 Early & %50 LateLate
New Reliability New Reliability MeasureMeasure
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-150 -50 50 150 250
Delay (sec)
0% xthD
Earliness IndexEarliness Index
1000 x
All lateAll late
All earlyAll early
0x
100x
New Reliability New Reliability MeasureMeasure
Which distribution is ideal from the perspective of a passenger?
SlimSlim WideWideNormalNormal
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-350 -150 50 250
Delay (sec)
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-350 -250 -150 -50 50 150 250 350
Delay (sec)
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-350 -250 -150 -50 50 150 250 350
Delay (sec)
Cumulative Frequency Distribution
0%
20%
40%
60%
80%
100%
-150 -50 50 150 250
Delay (sec)
New Reliability New Reliability MeasureMeasureWidth IndexWidth Index
%90th%90th
%10th%10th
HeadwayScheduled
DD 1090
A Real ExampleA Real Example
Width IndexWidth Index
Stop ID: Stop ID: 26092609
Earliness IndexEarliness Index
1.39%WI
For not frequent services “delay” should be usedFor not frequent services “delay” should be used
2.37%xI
0%
20%
40%
60%
80%
100%
-200 0 200 400 600
Delay (sec)
Cu
mu
lati
ve F
req
uen
cy
Average Headway = 13:30Average Headway = 13:30
Average Delay (sec) = 60Average Delay (sec) = 60
On-time Performance = %90.5On-time Performance = %90.5
LOS grade = BLOS grade = B
A Real ExampleA Real Example
Width IndexWidth Index
Stop ID: Stop ID: 26092609
Earliness IndexEarliness Index
3.81%WI
For frequent services “headway” should be usedFor frequent services “headway” should be used
6.47%xI
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
-400 -200 0 200 400 600
Headway Deviation (sec)
Cu
mu
lati
ve F
rew
uen
cy
Average Headway = 6:41Average Headway = 6:41
Average Delay (sec) = 51Average Delay (sec) = 51
Headway Adherence = Headway Adherence = 0.410.41
LOS grade = ELOS grade = E