California Department of Transportation

Typical VideoSync Analysis

Typical VideoSync Analysis - Detector Artifacts Uncovered

Below are a instances where a sidefire radar detector (just downstream of the loops) detected a “phantom” vehicle in lane 1 when there was none. Note in all cases there is a semi-truck in a closer lane. Even the detector developer was apparently unaware of this artifact.

Graphics for Typical VideoSync Analysis
Graphics of detected moving cars on the freeway Graphics 2 of detected moving cars on the freeway Graphics 3 of detected moving cars on the freeway Graphics 4 of detected moving cars on the freeway

Sample VideoSync Analysis - Radar Flow Rate

The graph below was generated by pasting VideoSync tabular data into Excel. This shows that the total 30 seconds volumes across 5 lanes generated by the radar unit are fairly accurate and the total “missed” and “phantom” vehicles almost exactly cancel out. This indicates this radar unit appears adequate during this period for generating the 30 seconds flow data typically used by TMCs.

Graph of Aggregate 30 seconds flows across 5 lanes

Sample VideoSync Analysis - Radar-Based Occupancy

Graph of ratio radar occupancy to true occupancy
Graph of Ratio radar to real occupancy, all lanes

The bar chart indicates the ratio of the radar occupancy to real occupancy varies dramatically by lane. The graph shows that the ratio of the total (5 lane) occupancy to the real occupancy could vary by almost 20% between 30 seconds sampling periods. This high variance indicates that this occupancy data is not functional for most quantitative purposes, even with the application of a “fudge factor”.