When some transit agencies being down the path of deploying a CBTC solution, they assume their engineers understand their operational requirements and begin writing a technical specification.
This assumption is wrong.
Frontline personnel (such as train driver or maintenance personnel) understand the daily operational needs of the Transit Agency because they operate the system day in and day out
Transit agencies must extract the needs and priorities of these frontline personnel and this is the primary objective of a ConOps.
The impact of not creating a ConOps is:
Missing functionality
Missing functionality will surface at the end of the project when it's too late
Increased cost to implement missing functionality
CBTC will operate less than expected
Finally, a ConOps is not an engineering document. It's a document written for a lay person who can understand what the transit agency needs operationally.
In order to understand the type of CBTC appropriate for your property, a ConOps is an essential tool.