1. Bus Service Reliability Developing new performance measures Unreliability Vs. Bus Bunching Meead Saberi K. meead@pdx.edu

2. Bus Trip Autopsy

3. Bus Trip Autopsy Unreliability sources Bus closes the door and is ready to leave Bus stops and opens the door Bus leaves Non-stop trip Dwell time Clearance time Delay in Arriving

4. Study 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

5. Route-Level Trip Time (inbound trip) Average trip time = 42:03 Standard deviation = 05:11 Coefficient of Variation = 0.12 90 th % - 40 th % (Layover) = 08:51

6. Route-Level Trip Time (outbound trip) Average trip time = 45:25 Standard deviation = 07:58 Coefficient of Variation = 0.17 90 th % - 40 th % (Layover) = 16:31

7. Developing New Reliability Measures

8. Current Reliability Measures Proposed by HCM and TCQSM On-Time Performance Headway Adherence Stop-level Delay = Actual Arrive Time – Scheduled Arrive Time Stop-level Delay = Actual Headway – Scheduled Headway

9. Current Reliability Measures Proposed by HCM and TCQSM On-Time Performance Stop-level Delay = Actual Arrive Time – Scheduled Arrive Time

10. Current Reliability Measures Proposed by HCM and TCQSM Headway Adherence Stop-level Delay = Actual Headway – Scheduled Headway

11. Current Reliability Measures Proposed 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.

12. New Reliability Measure Which distribution is ideal from the perspective of a passenger? %100 Early %100 Late %50 Early & %50 Late

13. New Reliability Measure Earliness Index All late All early

14. New Reliability Measure Which distribution is ideal from the perspective of a passenger? SlimWideNormal

15. New Reliability Measure Width Index %90th %10th

16. A Real Example Width Index Stop ID: 2609 Earliness Index For not frequent services “delay” should be used Average Headway = 13:30 Average Delay (sec) = 60 On-time Performance = %90.5 LOS grade = B

17. A Real Example Width Index Stop ID: 2609 Earliness Index For frequent services “headway” should be used Average Headway = 6:41 Average Delay (sec) = 51 Headway Adherence = 0.41 LOS grade = E

18. Thank you