Carbon and crowding – a potential implication of banning short-haul flights

On May 23rd, France’s ban on short-haul flights on routes that had rail alternatives taking less than two and a half hours came into effect. While the ban only affects a handful of routes, similar plans might be discussed elsewhere amid major pressure on aviation in Europe to reduce CO2 emissions.

Connectivity facilitates wide ranges of social and economic interactions that would otherwise be impossible, or very costly. Improved connectivity brings economic and social benefits, such as creating jobs, enabling tourism, increasing competitiveness and trade. Aviation provides important connectivity both within and across countries but (currently) comes at the cost of high carbon emissions.

Rail travel has the potential to cut emissions by replacing flights, but its expansion may also come at a high economic cost, involving new infrastructure, with embodied carbon emissions and long lead times. Between the environmental benefits of replacing short-haul flights with train journeys, and the high cost of expanding rail travel, what is the right balance to strike?

Flights under two hours made up 42% of ‘European’ passenger seats in May 2019

As a thought experiment, we considered what the impact would be on the use of major rail termini, if all the passengers from short-haul flights were to travel by rail instead. Banning flights that are under 2 hours (which we note is a longer flight time than those flights affected by the French ban) clearly would not mean all passengers would switch to rail travel between the same origin and destination. Instead, some journeys would not be made at all, and other journeys would change their destination. However, this is a useful exercise to show the importance of short-haul flights to European connectivity. An interesting challenge to these “flight-banning” policies is: is there enough capacity in the rail network to meet the displaced traffic, and what might be the cost of increasing that capacity?

Using flight data from May 2019, we identified over 33,000 total flights that departed from or arrived in Europe. Over 10,000 (or over 32%) of flights are shorter than two hours. These short-haul flights made up 12% of the total flying time, and 42% of weekly seats – a significant proportion.

You can explore this flight data yourself: The dashboard below shows the flights departing from 10 major airports with a flight time that is specified by the user, both direct flights and connections within the flight time cut-off chosen. Tick “direct flights only” to see the top 10 direct routes and passenger numbers.


Banning short-haul flights would increase the number of rail passengers significantly but the number is very sensitive to the chosen cut-off

Using the weekly number of arriving and departing passengers on short-haul flights for each of the major airports in nine cities, we matched the numbers against the weekly number of rail passengers for the major international train stations. Based on our analysis, banning short-haul flights could increase the number of rail passengers significantly: by 53% in Paris, and by almost four times in London if the chosen cut-off is for a two hour flight time. The detailed results of this exercise are shown in Table 1. Even if only half of passengers switched to equivalent train travel, the impact would be very big.

Source: Frontier analysis of Consumer Choice Centre and OAG data

However, if only flights of one hour or less are chosen, the impact reduces to:

Widespread bans on short-haul flights could require large investments into the rail networks

The implications of this thought experiment is that even a relatively small change away from aviation would have substantial implications for international rail networks if any flight ban was for sufficiently long duration flights. Given the potentially large increase in passenger numbers, existing rail networks and stations may not have the capacity to facilitate the movement of passengers from air to rail. Thus, large investments into the rail networks would likely be required before widespread bans on short-haul flights under 2 hours become feasible, unless there is widespread change to journey patterns and/or reductions in overall trip making.

We have not considered the embedded carbon implied in potentially meeting the increased demand for train travel, or the economic costs of not doing so. What this simple analysis shows is how efficient (in terms of land-use), aviation is for moving people across Europe: while banning short-haul flights might seem like a simple and attractive policy option for addressing climate change, the effects on Europe’s international rail networks should be carefully considered first to avoid unintended consequences.