1. Determination of Number of Probe Vehicles Required for Reliable Travel Time Measurement in Urban Network

2. Determining the Number of Probe Vehicles for Freeway Travel Time Estimation by Microscopic Simulation

3. Conclusions the minimum number of probe vehicles necessary is determined by the type of travel time distribution. the variance of the distribution would affect the minimum number of probe vehicles needed despite the type of distribution. the stability of the distribution would also affect the minimum number of probe vehicles necessary.

4. Factors Affecting Minimum Number of Probes Required for Reliable Estimation of Travel Time

6. Ideas Optimize the combination of # of vehicles and sensor spacing Independent variables: – # of probes – Sensor spacing Dependent variables: “Error” How to define “Error”? (variance) How to relate “Error” to # of probes and Sensor spacing?

7. Information Information from probe: – For each probe i, V i, x i, at any instantaneous time t 0 – For each probe i, Tti in time period t 0 -t 1 Information from detector: – Vt (time mean speed) in the previous short time period t 0 -t 1 – Occ. and Flow – Spacing

8. Objectives Online travel time prediction Offline travel time estimation Data Simulation Trajectory

9. Alternatives: