Here is a very simple question, that may be harder to answer than you think: why would you take a 4 to 5 hour train ride when you can fly an hour? In the UK, that is roughly the same travel time from London to the Central Belt of Scotland (or Glasgow and Edinburgh as its more commonly called). In 2019, nearly 1.2 million people flew between London Heathrow and Edinburgh airports, so some people clearly do choose to fly. Sadly, despite my research, there are no similar figures for either the East Coast or West Coast Mainlines between London and either Scottish city.

Data from the National Travel Survey shows how the mode by which people use changes in accordance with the distance of the trip, while for all trips under 350 miles the car is the dominant form of travel, and rail comes into its own between 250 and 350 miles, over 350 miles air travel dominates.

This indicates that, rather obviously, the door-to-door journey time is important. Under 350 miles, other factors on the air trip come into play: travel to the airport outside of the city, time to go through baggage and security, and going through baggage claim at the other end. Not to mention boarding and disembarking at either end through a limited set of doors.

But over 350 miles, the airport-to-airport travel time becomes much more important. as it makes up a greater proportion of the total trip and the journey time savings become greater. Whereas intercity trains in the UK usually max out at 125mph (High Speed 1 being a notable exception), a modern airliner can max out at 550mph at 36,000 feet.

A less well-known advantage, but one that is obvious once you think of it, is that aircraft can fly point-to-point. In practice, more general air corridors with degrees of vertical separation are in place that means travel isn’t quite point-to-point, but a plane flying from Heathrow to Glasgow will do it near enough in a straight line. Meanwhile, if the railway line from Euston to Glasgow were straight, it would smash straight through Manchester, cut the Lake District in half, clip the southern edge of Derby, and have a bridge across Morecambe Bay. Not only does this add time and distance, but in some instances can add an interchange penalty where the there are no direct services.

In the context of the UK, another factor is the need to cross water. This is particularly an issue crossing to Belfast and other areas of Northern Ireland from Great Britain, where even the shortest ferry crossing of the Irish Sea is over an hour and a half, whereas the flight time from London to Belfast is around an hour and a quarter. The same can be said of flying to the Scottish Islands, and to the Isles of Scilly where in 2021 the air route to Lands End was the busiest air route in the country.

This is all before you get into the issues around the relative cost of journeys by different modes of transport. That is a well-documented story that I will not repeat here. Needless to say that even if there are deals to be made on trains, the perception of the costs is very real indeed.

Fundamentally, travellers wish for a pleasant travelling experience, that poses the minimum cost in terms of money, time, and convenience. Whilst the ideas posed in the Union Connectivity Review in terms of bridges across the Irish Sea and the like are clearly mad, there is a semblance of logic to them. Cut down on internal air travel by reducing barriers faced by other modes of transport. That way, if long distance internal travel is to take place, it should be done by low carbon modes. That is something we should all aim for.