PROBABILITY OF REAL-TIME DATA AS A FUNCTION OF HOURLY VOLUME, ASSESSMENT OF THE I-95 VEHICLE PROBE PROJECT DATA

摘要

The Vehicle Probe Project (VPP) is an outsourced traffic monitoring system established bythe I-95 Corridor Coalition and has been active since July 2008. By contractual agreementwith the vendor, INRIX Corporation, travel time and speed data are provided to minimumquality specifications whenever traffic flow exceeds 500 vehicles per hour (vph). Themonthly validation program has confirmed the quality of the data by comparing VPP dataagainst travel times collected using BluetoothTM traffic monitoring equipment, but typicallyduring high volume periods when congestion is likely. Validation has not been confirmed forminimum flow conditions (less than 500 vph) due in part to lack of accurate volume data aswell as the low probability of observing traffic congestion at low volumes. The VPPprovides an indication of real-time data by the score attribute. When score is equal to 30, thetraffic data is based on real-time information. A score less than 30 indicates reliance onhistorical data. Studies have shown that traffic data based primarily on historical data do notmeet minimum quality specifications during moderate and severe congestion. By usingvolume data from the Maryland State Highway Administration and the Delaware Departmentof Transportation from permanent count locations, the likelihood of acquiring real-time data(as evidenced by score equal 30) as a function of hourly volume is established.