Anything involving approaching Liverpool Street on the circle line from the West going into the mainline platforms. I'm specifically thinking of Euston to Liverpool Street but I assume it applies to kings cross st pancras and probably farringdon? 15 mins to go between those platforms (which only involves about 10 steps) is frankly ridiculous.
Let's look at Euston to Liverpool Street. Current minimum connection time is 43 minutes consisting of:
Euston station connection time 15 minutes
Euston to Liverpool Street 13 minutes
Liverpool Street connection time 15 minutes
Euston Square to Liverpool Street takes 10 minutes on the Met/Circle/H&C during the day there seems to be a train at least every three minutes.
The walk from the train to Euston Square Underground station needs to be considered. The connection time has to consider that you might alight the train from the north end of an 11 car Pendolino on platform 1 and have to walk along the platform, up the ramp and across the concourse. Then negotiate the Euston Square Gardens and cross Melton Street before walking along Euston Road to the underground station. No running, wait for the pedestrian crossing to go green before crossing the road! I don't think there's any slack in the 15 minutes at Euston.
You might strike lucky with a train pulling in as you arrive on the platform. On the other hand you might arrive just as the doors close and have to wait three minutes. So 13 minutes for that component is appropriate.
The question is whether the 15 minutes at Liverpool Street too long? From the Met/Circle/H&C it doesn't take 15 minutes if you know where you're going. But the interchange time also has to take into account someone who ight be using the Central Line or Elizabeth Line where it takes much longer. The minimum time should not require you to walk or run up and down escalators.
You can do Euston to Liverpool Street in under half an hour, if everythihg goes well. But I'm not convinced that should be the default. I'd expect most 'normal' passengers to take about 30-35 minutes meaning 43 minutes is about right.
Perhaps an alternative would be to make advance tickets also valid on earlier services on connecting legs.
I agree, although there would need to be clear guidance on what a connecting leg is. Ideally connecting legs would not have reservations allowing an appropriate train to be taken, but that could have other unintended consequences.
They generally already are.
Many trains that historically did not have reservations now have them to enable Advance tickets to be sold for local journeys on those trains. This then has the unintended consequence of producing a 'mandatory reservation' for the connecting service.