Title

Accuracy and Precision of the Transit Tracker System

Authors

David T. Crout

Document Type

Journal Article

Publication Date

2007

Subject Area

infrastructure - track, infrastructure - vehicle, planning - signage/information, mode - bus, mode - rail, mode - mass transit, mode - subway/metro

Keywords

Vehicle locating systems, TriMet (Portland, Oregon), Tri-County Metropolitan Transportation District of Oregon, Transit, Tracking systems, Real time information, Rail transit, Public transit, Precision, Passenger counting, Motor bus transportation, Mass transit, Local transit, Intracity bus transportation, Intercity bus transportation, Bus transportation, Bus transit, AVL, Automatic vehicle location, Automatic passenger counting, Automatic location systems, Arrival times, Accuracy

Abstract

The accuracy and the precision of Transit Tracker, the Internet- and telephone-based real-time arrival information system of the Tri-County Metropolitan Transportation District of Oregon (TriMet), are analyzed. Although Transit Tracker estimates the arrival times of both bus and rail vehicles, this analysis is limited to bus vehicles. Archived data from TriMet’s automatic vehicle location (AVL) and automatic passenger counter systems were used to compare actual bus arrival times with Transit Tracker estimates drawn from logs created in the estimation process. Accuracy was evaluated primarily by calculating the mean of the difference between the actual bus arrival times and the arrival times estimated by Transit Tracker. Precision was determined largely by the degree of variation in the estimates and measured by the standard deviation of the difference between the actual bus arrival times and the arrival times estimated by Transit Tracker. Finally, an arrival estimation error model was developed to test the effects of a series of factors on the degree of estimation error.