It would otherwise not be possible for the second express service to call at Wrexham due to the infrastructure constraints of the single track between Wrexham and Chester.
Fel arall ni fyddai’n bosibl i’r ail wasanaeth trên cyflym alw yn Wrecsam oherwydd y cyfyngiadau ar y seilwaith, sef y trac sengl rhwng Wrecsam a Chaer.