[danpalmer]

I wouldn't be surprised if Google accounts for the London Marathon. Does it account for the opening night of a new show in the West End? I highly doubt it.

I don't think Google maintain their own data for rail travel, and the data sources aren't that good, so I doubt they'll be accounting for engineering works unless either they are scheduled far in advance or they've been happening for a while.

In my experience it takes time equivalent to a bunch of people having a crap journey and Google collecting that data for Google's instructions to change, they're not pre-emptive based on expert knowledge, they're reactive based on collected data.