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

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

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.

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

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?

Information

• Information from probe:– For each probe i, Vi, xi, at any instantaneous time t0

– For each probe i, Tti in time period t0-t1

• Information from detector:– Vt (time mean speed) in the previous short time

period t0-t1

– Occ. and Flow– Spacing

Objectives

• Online travel time prediction• Offline travel time estimation

Data

• Simulation• Trajectory

• Alternatives: