Original User: kylie
It sounds like the vehicles are visible on the map, so instead of adding an external data source and filtering that to get your subset of vehicles, create a filtered data source off the layer in the map, and use that in your list.
To create a filtered data source off the layer in your map, edit the operation view and configure the map widget. In the Configure Map dialog's Data sources tab, select the data source of which you want to create a filtered version. Under settings, for Filters click Add. Name and create your filter as you did for the stand-alone data source above, and click OK to close the Query Definition dialog.
Now when you configure the list, you will see a data source listed as part of the map that shows a filter icon, and your query's name. Select that as the source for your list.
This won't filter the data as displayed on the map, but only filters the data in widgets that use that filtered data as source.