Select Link Analysis

For the example of using the select link analysis to retrieve information about of network traffic conditions (24-hour basis), we will look at an example network where, after modifying the original network, the interchange ramps were explicitly included in the network. It is on these ramps that we will develop are select link analysis. The example network is shown:



For the ramps, we begin by querying to determine the node numbers that identify the ramp in question.



With this information, we then need to modify the Tranplan control file to reflect our desire to assign only traffic to the network the uses this particular link in the model.

Note that the modification are only required in the assignment phase of the process.


$LOAD HIGHWAY SELECTED LINKS
$FILES
    INPUT FILE = HWYNET, USER ID =$NET90X.BIN$
    INPUT FILE = HWYTRIP, USER ID =$TOT90X.TRP$
    OUTPUT FILE = LODHIST, USER ID =$TOTAL.BIN$
    OUTPUT FILE = SELHIST, USER ID =$SELHIST.BIN$
$HEADERS
    'RUN FOR SELECT LINK ANALYSIS'
            'USING'
    'LOAD HIGHWAY SELECTED LINKS'
$OPTIONS
$PARAMETERS
    IMPEDANCE = TIME 1
    LOAD SELECTED LINKS = 492-493
    ONE WAY SELECTED LINKS = 492-493
$END TP FUNCTION

$BUILD SELECTED LINK TRIP TABLE
$FILES
    INPUT FILE = HWYTRIP, USER ID =$TOT90X.TRP$
    INPUT FILE = SELHIST, USER ID =$SELHIST.BIN$
    OUTPUT FILE = SELVOL, USER ID = $SELOUT.BIN$
$HEADERS
    'RUN FOR SELECT LINK ANALYSIS'
            'USING'
    'BUILD SELECTED LINK TRIP TABLE'
$OPTIONS
    OR LINKS
    PRINT TRIP ENDS
$PARAMETERS
    SELECTED LINKS = 492-493
    SELECTED PURPOSE = 1

$END TP FUNCTION
$LOAD HIGHWAY NETWORK
$FILES
    INPUT FILE = HWYNET, USER ID =$NET.BIN$
    INPUT FILE = HWYTRIP, USER ID =$SELOUT.BIN$
    OUTPUT FILE = LODHIST, USER ID =$OUT.BIN$
$PARAMETERS
    IMPEDANCE = TIME1
$END TP FUNCTION

Following this format and using the output file for the LODHIST from the load highway selected links as the input to the Netcard option will bring the assigned traffic information for only trips using the selected link into MapInfo for analysis.

Looking at the results in MapInfo, the previous assignments for the interchange area links are shown



And the loaded assignment loading only trips that use the selected link



This information can be used when examining the entire network to determine where trips are starting and ending within the network by developing band widths for the loaded volumes using the thematic mapping function.

     Select any of the options to receive more information or click on the back button to return to the GIS analysis page or the site map button to go to the site map.