Research by Transport Scotland estimates that, even with the increased speed limit for HGVs, average speed cameras would reduce carbon dioxide emissions from traffic on the A9. Particulate emissions and nitrogen oxide would also reduce, leading to less local air pollution. 
Gina Hanrahan, Climate and Energy Policy Officer at WWF Scotland said:
Alongside the clear safety benefits, enforcing speed limits on trunk roads using average speed cameras and other tools is an effective and cost effective way to reduce climate emissions as well as fuel costs for motorists.
"To reduce health-threatening levels of air pollution and our meet our climate targets, the use of average speed cameras and other approaches to help reduce excessive speeds should be seriously considered on other major roads across Scotland."
Notes to Editors
 Transport Scotland research