This is where a regular timetabled service will be delayed through scripted external circumstances forcing the player to claw back time for the rest of the journey. Circumstances include: Priority given to another train knocking your service off time, more freight running in between passenger services and scripted late running AI trains spawning into the map. Inspiration comes from ECW where the AI 05:37 to Ore is given priority over the 05:36 to Brighton, this causes delays for both 05:36 and a later service to Seaford which I found interesting although I’m unsure whether it was intentional or a bug.
Yes, I agree to to the idea of more random events in TSW (some which do delay the train or not). Another recent thread discusses speed restrictions and cancelations due to weather chaos. A little bit more life and unforseeable events in TSW would enhance the immersion much. Optionally people could adjust or turn off these events however they like just like in ETS2.