I've noticed that, during one of the many weekend closures on the Great Eastern Main Line on the 13th April (the closure this time being between Ipswich and Norwich), it doesn't appear possible to get an itinerary on alternative routes such as to complete the journey entirely by train (e.g. via Lowestoft). The only route I can get an itinerary on is via the Rail Replacement Buses. The Replacement Buses take around an hour and a half, whereas travelling via, e.g., Lowestoft takes around an hour longer than that. So, perhaps for most passengers, not such an attractive option. But what about those with bikes, or pushchairs, or similar bulky luggage? This often can't be accommodated on Replacement Buses. That means that someone with a bike for instance would think that there is no way for them to travel, at all. In practice, I would have thought that a ticket from Norwich to stations between Ipswich and London would be accepted for travel via Lowestoft, especially if the passenger has a good reason for not wanting to take the Bus. That then raises the question of why booking engines aren't even allowing it as a potential route. Perhaps someone with access to the industry data can work this one out.