Determining the number of probe vehicles for freeway travel time estimation by microscopic simulation

Using probe vehicles to collect real-time traffic information is considered an efficient method in real-world applications. How to determine the minimum number of probe vehicles required for accurate estimate of link travel time is a question of increasing interest. Although it usually is assumed that link travel time is normally distributed, it is shown, on the basis of simulation results, that sometimes this is not true. A heuristic of determining the minimum number of probe vehicles required is developed to accomodate this situation. In addition, the impact of traffic volume on the required probe vehicle number is discussed.