Possible Clues:

• Control number of carriages allowed in halt
• 'Express' in support for confinement
• Self-discipline to take exercise during holiday
• It calls for control when what's left is wet before the tea
• Check transport during time off work
• Instruct the others to go outside and check
• Prop accepting coach's controlling influence
• It's controlled by the railway among all the rest
• Start rain as an impediment
• One locomotive among the rest shows such control