1. TRAVEL TIME VARIABILITY AFTER A SHOCK: THE CASE OF THE TWIN CITIES RAMP METERING SHUT OFF David Levinson, Lei Zhang Department of Civil Engineering University of Minnesota Levinson, David and Lei Zhang (2001) Travel Time Variability After A Shock: The Case Of The Twin Cities Ramp Meter Shut Off,Travel Time Variability After A Shock: The Case Of The Twin Cities Ramp Meter Shut Off The Network Reliability of TransportThe Network Reliability of Transport (2003) Pergamon (editors Yasunori Iida and Michael Bell) (Presented at First International Symposium on Transportation Network Reliability, Kyoto, Japan July 30- August 1 2001). http://nexus.umn.edu/Papers/Variability.pdf

2. 1. Introduction  Ramp Meter Shut Off Experiment TwinCities Oct. to Dec., 2000  Travel Time Variability  Studied Freeway Locations

3. 2. Measuring Travel Times 2.1 Overview Trip Travel Time = Freeway Mainline Travel Time, metering-off Ramp Delay + Freeway Mainline Travel Time, metering-on Freeway Segment 1 Freeway Segment 2 Freeway Segment 3 Ramp 1 Ramp 2 Ramp 3 OD Trip 1 OD Trip 2 OD Trip 3

4. 2.2 Methodology  Ramp Delay Calculation: Queuing Diagram  Freeway Segments q-k-v Relationship Detector Field Length  OD Trips Synchronize Ramp Delay and Freeway Travel Time to Find Trip Travel Time

5. Notations t:index of time of day (5 minute intervals) n:index of days s:ramp status, off = without, on = with ramp meter control  :travel time std():compute standard deviation ave():compute average V:inter-day travel time variation v:intra-day travel time variation D:difference of inter-day travel time variations (off - on) v:average of intra-day travel time variation

6. 3. Travel Time Variations  Inter-day Travel Time Variation  Intra-day Travel Time Variation

7. 3. Travel Time Variations (cont’d)  Comparing Travel Time Variations: Metering-On vs. Metering Off Inter-day: For Each OD Pair, There is a Vector of D t for Different t’s. Range-Median Graph Intra-day:

8. 4. Results 4.1 Inter-day Travel Time Variation  V off - V on > 0, statistically significant at level 0.01 for 103/124 OD Pairs: 26/45 for OD Pairs 3 miles  Long Trips vs. Short Trips (<=3 miles)  Range-Median Graph for Each Freeway 4.2 Intra-day Travel Time Variation  v off > v on  Long Trips vs. Short Trips

9. Inter-day Travel Time Variation: I494 Eastbound and Southbound

10. Inter-day Travel Time Variation: I494 Westbound and Northbound

11. Inter-day Travel Time Variation: TH169 Northbound

12. Inter-day Travel Time Variation: TH62 Westbound

13. Intra-day Travel Time Variation: I494 Eastbound and Southbound

14. Intra-day Travel Time Variation: I494 Westbound and Northbound

15. Intra-day Travel Time Variation: TH169 Northbound

16. Intra-day Travel Time Variation: TH62 Westbound

17. 4. Results (cont’d) 4.3 Benefit Estimation for the Reduction on Inter-day Travel Time Variation (on average, 1.82 minutes per trip)  Small et al. (1999): $0.21 per minute of travel time standard deviation  Monetized benefits of improved travel time reliability: $0.38 per trip 900,000 trips per PM peak in the Twin Cities 10 million dollars per year, savings during PM peak only 4.4 A Simple Approach to Incorporate this Travel Time Reliability Improvement into Ramp Meter B/C Analysis Apply a markup factor of 1.35 to value of time

18. 5. Conclusion  Ramp Metering Improves Travel Time Reliability  Further Research on Monetizing the Value of Travel Time Reliability Contact Information David Levinson Department of Civil Engineering, University of Minnesota 500 Pillsbury Drive SE, Minneapolis, MN 55455 E-mail: levin031@tc.umn.edu Tel(O): 612-625-6354