ITS Research Program, UW

Kalman Filter
Speed Estimation from Single Loop Data

About this Kalman Filter:

This Kalman Filter is a C program component which can be incorporated into existing code to produce speed estimates from single loop data, such as that obtained from loop_client. The filter uses volume (in vehicles/hour) and occupancy (as a percent) to pr oduce a speed (in miles/hour). The download package includes a demonstration program using sample data. Also included is a paper about Kalman Filters (PostScript format), "A Statistical Algorithm for Estimating Speed from Single Loop Volume and Occupancy Measurements," by Dr. Daniel J. Dailey .

Kalman Filter is Copyright, 1996, ITS Research Group, University of Washington

System Requirements:

• Operating System: Unix
• Total Disk Space Required for Download: 300 KB
• Memory Required:
• Network Connection Type: TCP/IP

Downloading Kalman Filter:

• As a TAR format file (297 KB).

Installing Kalman Filter:

Place Kalman Filter in the desired directory, and unpacking it by running the command: tar xf kalman.tar.

Operating loop_client:

Here is some sample output from the Kalman Filter. (This output is not updated.)

712: vol =  1980 veh/hr, occ =  20.5%, speed =  42.64 mph, length =  21.04 ft
713: vol =  1620 veh/hr, occ =  16.1%, speed =  43.80 mph, length =  20.85 ft
714: vol =  1800 veh/hr, occ =  15.5%, speed =  46.39 mph, length =  19.33 ft
715: vol =  1260 veh/hr, occ =  15.4%, speed =  42.59 mph, length =  24.80 ft
716: vol =  1260 veh/hr, occ =  17.5%, speed =  38.62 mph, length =  25.03 ft

Related Information:

TrafNet is a Windows program which takes the loop data and displays it as a graphic representing the freeway system. TrafNet is available for free downloading.

To get a snapshot of current traffic conditions over the WWW, check out the Washington State Department of Transportation Metro Traffic Flow Map.