The tube also can be extremely busy (sometimes with very noisy passengers) due to sales in shopping centers or due to sporting matches, exhibitions, etc.
This also calls for some value-assignment to transport methods. E.g.: cycling is preferable to tube, but more than light rain benefits tube, but more than an X minute / X% delay swings benefit to cycling. The real variable here is how long a commute takes -- so, is/was there a tangle in the tube when that was the recommendation.
Closing the loop on predictions/recommendations is a common problem in any monitoring/alerting application. For all the ballyhoo on the online dating problem, I'd warrant that getting closure on the dating experience is where most sites fall flat.