Match the window before the distance.
Choose whether the connection follows corridor travel or a named city routine, then keep the broad endpoint consistent in the profile.
Starting around Cardiff
At the Cardiff end, use “The south-Wales corridor supports regular movement, but each centre has distinct local routines.” as a scheduling prompt rather than a claim that the whole route is local.
Planning around Newport
At the Newport end, choose whether the connection follows corridor travel or a named city routine, then keep the broad endpoint consistent in the profile.
Compare both local pages
Treat each town as a separate local context, then use the overlap planner rather than assuming the full route is convenient at every time of day.