5. Conclusions
This paper set out to study the difference in costs between aircraft noise and road noise. When applying a meta-regression to the 90 NDI estimates of 53 studies the results indicate that there is a difference in the range 0.40e0.60 in terms of NDI, which means that aircraft noise costs an additional 0.40 and 0.60 percent more per increased dB than road noise. Noise valuations are resource intensive, they take time and require costly data gathering. In light of this, valuations are not always available for both road noise and aircraft noise. Knowing the cost of noise is important. Policy makers need this knowledge when implementing noise reduction schemes and planners when determining where to construct new roads or expand airports. The knowledge of a relation between road noise and aircraft noise can serve as a rough conversion “multiplier” when aircraft noise estimates are not available, but road noise estimates are, or vice versa. Thus it may be a convenient tool for planners and policy makers when it comes to noise regulation and traffic planning.