Vehicle Routing - Summary
The routing add-in uses several worksheets in an Excel workbook. This page describes the sequence of construction of these pages. When the page images are small, click the image for a larger display.
 The modeling process begins by choosing the Start command on the Vehicle Routing menu. This command performs two functions. It creates a worksheet that contains a list of general instructions. The Distance Button on the Start worksheet creates the Distance worksheet. When the Start command is used for a workbook that already contains add-in worksheets, all the buttons in the workbook are re-created. This eliminates linking problems when a workbook is opened on a computer other than the computer that created it. Before closing an add-in workbook, it is good practice to choose the Finish command. This deletes buttons on the worksheets. Workbooks without buttons will open on any computer, while workbooks with buttons will work successfully on only the computer that created the buttons. The Start command or the Links command of Excel will correct link errors. Models that use geographic coordinates contain the user-defined function "GreatCircleDistance". The function will not work on a computer different than the computer that created the workbook. The Finish button removes references to this function and the Start button restores the references.

Part of the Start Page is shown below. The first step is to make a distance worksheet by clicking the button.

Distance Worksheet

 The Make Distance Worksheet button on the Start worksheet creates the Distance worksheet. The distance worksheet accepts map locations. Cartesian or Geographic coordinates may describe locations. Distances may be computed by the length of straight lines between coordinates (Euclidean), the length of the curved path on the surface of the earth (Great Circle Distance), or with a matrix whose distances are obtained from some other source (perhaps Google Map). A workbook may have more than one distance worksheet. The examples on the left illustrate distances computed with the Euclidean metric. The map data on the distance worksheet of the example has 646 entries. Each entry describes an intersection of major highways in the Austin area. The locations are described with geographic coordinates. Distances are measured in miles.

Customer

 When the distance worksheet is created, a second worksheet called the Customer worksheet is also created. For many problems, customers or deliveries are not located at the same coordinates as locations that describe the map. This second worksheet is created to hold the independent coordinates of customers. For the example we make the customer locations the same as the map locations. The data including the names and coordinates are transferred from the distance worksheet. For this reason the cells are colored yellow.

Planning Data Worksheet

 The second step is to create a Planning Data worksheet that holds data for a specific routing instance, perhaps the deliveries to be made on a given day. The data describes deliveries and vehicles (called trucks). There may be several trucks. Trucks have limited resources, such as capacity, and deliveries use up the resources.  The times available, early and late delivery times are on this worksheet. A duration penalty can be used to establish priorities between deliveries. The costs of penalty violations are also on this page. Each delivery location is associated with a map location on the Distance worksheet. Click the Make Plan button on the Distance worksheet to create a Planning Data worksheet.

Results Worksheet

 The third step is to create the Results and Model worksheets. Create these sheets by clicking the Make Model button on the Plan worksheet. Each Plan worksheet has unique Model and Results worksheets. The Results worksheet indicates the current route and the associated truck assignments and delivery times for the route. Buttons at the top of the worksheet call various heuristic processes that find solutions.

Model Worksheet

 The Model worksheet creates a form used by the Opt. Sequence add-in to search for good solutions. The Opt. Sequence add-in must be installed to find solutions. Download the add-in from the OM/IE add-in page or click the link at the left.

Map Worksheet

 A map of the route is created on a separate worksheet when the Map button is clicked on the Results or Model worksheets. Colors indicate the routes of different vehicles. An alternative to the Excel map, the add-in can create a program that is used with Google Earth to display a routing solution. The figure at the left was copied from the Google Earth.

The remaining pages of this section describe the features and implementation of the routing add-in.

Operations Management / Industrial Engineering
Internet
by Paul A. Jensen