Sometimes when you preview a new timetable it includes a section of a journey that shouldn't be there. This is often related to a bus running from one location, such as the depot, to the first stop that it picks up passengers. These are known as 'dead runs'.
To export the TransXChange without these, change export settings in your timetabling software. For example, in OmniTIMES, uncheck the "Identify Short Workings" option under the "Optimizations" panel, as shown below.
The TransXChange Export view in the OmniTIMES software, which some operators use to schedule their networks.
As a rule of thumb, all of the boxes in the "Optimizations" section of the export settings should be unchecked.