Air Departure Tax reduction in Scotland: noise impact assessment

1. Executive Summary

1.1.1. This report presents the findings of an assessment of the potential impact on noise levels of the Scottish Government’s plans to reduce the overall burden of Air Departure Tax (ADT) by 50%.

1.1.2. The assessment covers the five largest airports in Scotland (in terms of passenger numbers)^[1] and considered six^[2] alternative scenarios for a reduction in ADT. The hypothetical scenarios differ in terms of the bands (based on distance to destination with Band A representing short haul flights (from 0 to 2,000 miles) and Band B representing long haul (over 2,000 miles))^[3] to which the tax reductions are applied. The extent to which the reduced taxes will be passed on to passengers by airlines in the form of lower air fares are reflected by what the report refers to as “Full Pass Through” or “Zero Pass Through” scenarios. 

1.1.3. The six scenarios (not including the baseline scenario of ‘Do nothing’/existing tax levels option) considered in the assessment are as follows:

• Scenario 1a – 100% cut in Band A (Full Pass Through);
• Scenario 1c – 100% cut in Band A (Zero Pass Through);
• Scenario 2a – 100% cut in Band B (Full Pass Through);
• Scenario 2c – 100% cut in Band B (Zero Pass Through);
• Scenario 3a – 50% cut in Band A & Band B (Full Pass Through); and
• Scenario 3c – 50% cut in Band A & Band B (Zero Pass Through).

1.1.4. Departures from the Highlands and Islands are currently exempt from UK Air Passenger Duty (APD). The potential noise impact at Inverness Airport was excluded from the assessment on the working assumption that this exemption will continue when APD is replaced by ADT in Scotland and so Inverness is included in the baselines for 2018 and 2022 but not in the forecasts.

1.1.5. The likely changes to air traffic movements at the remaining four airports were estimated for each ADT scenario for the year 2022. These were then used to forecast the changes in the aircraft noise levels in the vicinity of each of the airports and compared to a ‘no-change’ scenario in which no changes were made to ADT and increases in passengers occur only from underlying market growth rather than tax reductions. 

1.1.6. The predicted aircraft noise levels were then combined with population projections within the vicinity of the airports to estimate the likely change in the numbers of people exposed to different levels of aircraft noise.

Noise level changes

1.1.7. The changes in aircraft noise levels in the vicinity of the airports are best demonstrated by noise contours. These are a series of lines which link geographical points experiencing equal noise similar to the way in which relief contours link areas of equal elevation on a topographic map. Each noise contour joins areas within which noise levels are above a specified value and areas between two contour lines represent defined intervals, e.g. 45 dB^[4] to 47.9 dB, 48 dB to 51.9 dB, etc. The larger the area enclosed by the contours, the wider the spread (and typically higher the number) of properties and people likely to be affected by noise.

1.1.8. Based on the total area covered by the contours, the scenarios resulting in the largest noise impacts have been identified to be: Scenario 3c (50% cut in Band A & B and B with Zero Pass Through) for Aberdeen Airport and Scenario 1c (100% cut in Band A with Zero Pass Through) for Edinburgh, Glasgow and Prestwick Airports.

1.1.9. These results, as expected, correspond with the economic assessment’s passenger movement forecasts from which forecast changes in air traffic movements (ATMs) have been derived. The largest increase in overall passenger movements from all airports was forecast to occur under Scenario 1c – where airlines do not lower air fares as a result of a tax reduction but instead invest in the development of routes applicable for Band A UK APD rates. Aberdeen Airport is the exception, where the demand response to lower air fares from an ADT cut (Scenario 3c) is expected to lead to greater increases in passengers (and subsequently ATMs) than from the supply side effect of route development.  

Impacts of additional noise exposure

1.1.10. Scenario 2a (100% cut in Band B, Full Pass Through) results in the smallest aggregate impact on noise exposure across all airports which is estimated to result in an increase in population exposed to L_Aeq,16h^[5] noise levels above 51 dB(A) of approximately 1,274, and an increase in population of approximately 1,577 people exposed to night-time noise (L_night) levels in excess of 45 dB(A)^[6]. This follows directly from the prediction that Scenario 2a would result in the smallest increase in both daily ATMs and the area covered by the 51 dB L_Aeq,16h and 45 dB L_night noise contour. 

1.1.11. The highest aggregate impact across all Scottish airports is observed under Scenario 1c (100% cut in Band B with Zero Pass Through), which is estimated to result in an increase in population exposed to L_Aeq,16h noise levels above 51 dB(A) of approximately 10,902, and an increase in population of approximately 11,875 people exposed to night-time noise (L_night) levels in excess of 45 dB. 

1.1.12. Predicted noise level increases may be at least partly offset by the potential impacts of improvements in the noise-efficiency of aircraft over time. These potential improvements are not considered in the assessment and are likely to result in a decrease in exposure to adverse levels of noise by 2022. However, these reductions would also be present in the no-change scenario and would therefore make no difference to the overall ranking of the tax and Pass Through scenarios.