1. When permanent vacancies occur on regular must fill positions or extra board positions, trainmen may elect by seniority option, to fill the vacancies in accordance with existing rules. However, until such time as there are no Reserve Board employes (either Tier I or Tier II) within the applicable zone where the vacancies exist, trainmen not working within that zone will not be permitted to transfer into the zone or be assigned to any vacancy under the applicable application and/or bulletin rules.Employes will not be permitted to exercise displacement rights outside of their current zone to another zone until such time as the other zone is exhausted of reserve board employes (either Tier I or Tier II). This exception however does not apply if an employe is unable to exercise seniority within his/her zone and the result would be the furlough of that employe.

The zone rights set forth in this Article are only in effect within a particular zone so long as there are employes assigned to a reserve board (either Tier I or Tier II). Once the applicable Reserve Board (both Tier I and Tier II) does not have employes assigned to such, other employes outside of the zone will be able to exercise their existing seniority rights to available positions.