One door. One bad decision. A nightmare commute explained.

OTTAWA - Small things can have huge implications. That's what O-train riders are learning with the brand new system. The city issued a statement explaining why trains were delayed and thousands were late for work on Tuesday morning. CTV's Graham Richardson provides a point by point thread on Twitter, explaining what went wrong.  One door. A terrible commute for thousands.

The story of one door....one bad decision...by one passenger....thousands of @OC_Transpo commuters affected in Ottawa

2. 8:05 am at UOttawa station customer "pushed open" doors while exiting train...door can't close @ctvottawa

3. A door fault can usually be fixed by an operator. Not this one. Two employees couldn't fix it. Train empties...problems start @ctvottawa

4. trains can't run with half open or "jammed" doors. Safety. So must close or you can't run.

5. 8:15 train "diverted". meaning both east and westbound trains had to share a track for 2.5km between UOttawa and Hurdman

6. Single track service means extra buses to deal with the crush of people piling up. Delays of 15-20 minutes. Passengers say much longer than that. Some waited 50 minutes for trains to pick people up at Tunney's.

7. full service restored by 9:15. @OC_Transpo says backlog cleared by 9:30.

8. @OC_Transpo hints the "dwell" time may be too short at UOttawa station. Says they will look at how long doors are open and whether they need to be open longer.

9. they apologize to the thousands of passengers this affected.

10. One door. One passenger. Thousands of commuters affected on day 2 of full operation of the LRT.

11. They point out doors close and open every day 86,000 times. I'm not sure if they're counting closing and opening as 2.

12. So this one instance...out of 85,999 others...wrecked your commute. More tonight @ctvottawa