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Problem: VRP solver with virtual start depots fails with time zones

Description

When a VRP (vehicle routing problem) layer with virtual start depots is solved on a network dataset with time zones, the solver fails with the message:

"Warning: Orders has orders that are in different time zones and Routes has routes with virtual start depots. The time zone for the start time of each of those routes is ambiguous since it depends on the first assigned order.
Error: Invalid input in the NA classes."

Cause

The VRP solver does not support using virtual start depots when orders are located in different time zones. This is because each route has the start time window defined by two fields 'EarliestStartTime' and 'LatestStartTime'. When the solver assigns orders to each route, it is assumed that start time window provided is fixed.

However, when a virtual start depot is used, the route start time is determined by the first assigned order of each route. If the orders are located in different time zones, the time zone of the route start time becomes unclear. Therefore, this is not supported.

Solution or Workaround

To use virtual start depots, turn off the time zone information in the data:

  • In SDC data, remove the reference to the time zones table:

    Remove the line

    Code:
    <sdc:TableDef id = "timezones" href = "streets.rsx\timezones.sdc"/>


    from the streets.rs file.
    Warning:
    Be sure to make a backup copy of streets.rs file before deleting the reference in case it becomes necessary to add the reference back in the future.

  • In FileGDB data, remove the Time Zone network attribute from the Attributes tab on the Network Dataset Properties window.
    Note:
    Once the time zone information is turned off, it is not advisable to use the historical traffic and live traffic information because it is assumed that all streets are in the same time zone. This causes the historical/live traffic data to return inaccurate travel times.