ITS Reseach Program, loop

ITS Research Program, UW

loop_client
Real-Time Freeway Sensor Information Over The Internet

About loop_client:

loop_client is a Unix program which provides occupancy, speed and volume data for individual loop sensors embedded in Seattle area freeways. The loop data is updated every 20 seconds. loop_client was written for BSD Unix and has been tested on VMS, HP U X and Solaris operting systems. It may require modification to function correctly on other operating systems.

loop_client acquires data from a server via a TCP connection over the Internet; the display is updated with new information every 20 seconds. Since only traffic information is transferred, updates are quick, with very little overhead.

loop_client is Copyright, 1996, ITS Research Group, University of Washington

System Requirements:

Operating System: BSD Unix, VMS, HP UX, Solaris
Total Disk Space Required: 150KB
Memory Required:
Network Connection Type: TCP/IP

Downloading loop_client:

You may download loop_client via the following mechanism:

As a TAR format file (82KB).

Installing loop_client:

Place loop_client in the desired directory, and unpack it by running the command: tar xf loop_client.tar. Check the README file for information on files which may need to be modified for specific platforms. From the its directory, type make to compile loop_client.

Operating loop_client:

Once you have installed (modified if necessary) and compiled loop_client on your computer, run the program ls_client. The usage for ls_client is as follows:

Usage: ls_client [-p port] [-h host address] [-r retries] [-b backoff]
       [-g G value] [-v] [-R]
       port = loop server port (default is 9004)
       host address = loop server host (default is research.ivhs)
       retries = retries on each connect attempt (0 is infinite) (default is 10)
       backoff = max interval between attempts (default is 64 sec)
       G value is used in calculating speed (default is 0.220000)
       -v = verbose, 
       -R = don't reconnect

You should not change the default port or host address values as this will result in incorrect results.

NOTE: As presently written, loop_client does not allow the user to request specific loops. Future versions will provide this functionality, and will be posted at this site.

Here is some sample output from loop_client. (This output is not updated.)

ES-111R:MMN___1: route: I-5, mile: 165.93, occ:  9.7, vol: 1620, speed: 65.7
ES-111R:MMN___2: route: I-5, mile: 165.93, occ: 18.3, vol: 2340, speed: 57.8
ES-111R:MMN___1: route: I-5, mile: 165.93, occ: 16.3, vol: 1800, speed: 57.6
ES-111R:MMN___2: route: I-5, mile: 165.93, occ: 16.5, vol: 2340, speed: 59.2

This output can be interpreted as follows:

The first item is the loop/sensor name (ES-111R is the cabinet, MMN___1 is NB lane 1, MMN___2 is NB lanes 2).
occ = occupancy (%, 1-100)
vol = volume (vehicles/hour)
speed = MPH

Related Information:

A Kalman Filter, which can be incorporated into existing C code, is available to produce speed estimates from single loop data

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.

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(April 8, 1997)