No carbon saved by diverting Heathrow passengers to Bristol

27 November   2009

Bristol airport’s argument that its expansion will ‘capture’ local passengers
who currently fly from Heathrow and other South East airports and save carbon
emissions has been dismantled in a new report released today.


Produced by Stop Bristol Airport Expansion, the study   [ read the Leakage report    ]   reveals that the expansion of Bristol airport (BIA) is highly unlikely to divert
much of this ‘leakage,’   but even if it did, the introduction of even one extra
route would actually increase rather than decrease the UK’s total carbon emissions.
All figures used are from public sources. [1,2]

Report author Jeremy Birch said:

"Bristol airport has always claimed that their expansion will be able to divert
most of this ‘leakage’ back from Heathrow and other airports and will ‘save’ greenhouse
gas emissions on car journeys – but a close look at the facts shows this assumption
simply doesn’t hold up.

"It’s very clear that expanding Bristol airport will not only fail to attract
passengers away from other airports, but   will actually increase the UK’s total
carbon emissions if even one extra route is introduced to accommodate ‘leaked’

"Local decision-makers need to take note that capture of this ‘leakage’ is completely
invalid as a justification for expansion of Bristol airport."

Currently 4.7 million South West travellers use airports in the South East each
year. The report reveals that even if the 2.8 million of these using Heathrow,
the closest SE airport, were diverted to Bristol, this would fall far short of
the 4 million extra passengers BIA is planning to handle by 2019.

The report illustrates the implausibility of diverting to Bristol more than 200,000
of the passengers currently using Heathrow as there is not enough demand in the
South West to make viable the routes being accessed from South East airports.

For example, most leakage is for long haul routes such as Hong Kong and Bangkok,
which require planes that cannot fly from Bristol’s short runway.   The large hubs
of Newark, Paris and Amsterdam are already served by Bristol but the large numbers
of locals using Heathrow to access long-haul destinations show they prefer direct
routes, a preference that is unlikely to change in the future.

Popular short haul routes accessed through Heathrow such as Munich, Frankfurt
and Zurich have previously failed at Bristol.

Introduction of just one of these services would increase total UK greenhouse
gas emissions unless a corresponding Heathrow service was removed. The leakage
is not sufficient to fill a daily scheduled service on any of the routes. Any
diverted traffic would only happen if Heathrow services were duplicates at Bristol,
so two planes would be flying instead of one.

If all the leakage was diverted back to the South West, it might save 13,700
tonnes of carbon dioxide from cars each year. However, one extra daily flight
would add over 14,000 tonnes of carbon emissions to the atmosphere.

Diversion of all Heathrow ‘leakage passengers would require at least 25 extra
daily routes, producing an increase of the equivalent of 750,000 tonnes of carbon
dioxide, which is 53 times the impact saved by reducing car travel.

The airport has argued that expansion would reduce leakage and emissions. Instead
it would be adding more short-haul outbound leisure routes that would have negligible
impact on the leakage and would significantly increase emissions.


For more information visit:  


 [1] How will expanding BIA impact on passenger ‘leakage’ from South West region
to South East airports
read the Leakage report    

[2] Main data sources (all figures used are from public sources). The major publications

Civil Aviation Authority (CAA) annual passenger numbers for BIA (

CAA Passenger surveys covering BIA for years 2000, 2003, 2008

Additional data from the 2008 survey used to compile the CAA report

Maps and distances from Cloudmade and Google