The ‘traffic light’ table presents a simplified synopsis of the regional impacts of the baseline and of the policy packages that have been analyzed for the Outlook, The table compares the baseline and the three policy packages in terms of the pattern of their regional impacts. It is not meant to provide a concrete predicament of a specific policy package.

The ‘traffic light’ table is the product of a judgmental process, i.e.

• Themes were operationalised by narrowing them down to specific issues. For example, air pollution is assessed using information on premature mortality which is attributable to urban air pollution, with suspended particulate matter smaller than 10 micrometers by 2030, and trends in sulphur dioxide emissions after 2030. 
• Estimates for the chosen  issues were derived from a visualisation system filled with modelling results for the Outlook. These were primarily considered at the level of 13 regional clusters, then checked at the 24 regional levels for the underlying distribution within regions.
• The projections for the next quarter century were compared to the current trend of a specific issue,to see the degree of change across baseline and policy packages. Three dimensions were taken into account.
  - First off, most weight was given to the change in environmental pressures between now and 2030 (direction and rate of change). 
  - Secondly, the 2030 and 2050 levels of environmental pressure were considered: would they come anywhere near to targets discussed in the Outlook? 
  - Thirdly, a more detailed check was carried out. Spatially, by checking for important hotspots within a regional cluster (by looking at the underlying results of the environmental modelling in terms of 24 regions), and temporally: would the situation become significantly worse before getting better? If such hotspots or bumps in time were indicated, then the traffic light score could never be higher than amber.
• For themes that feature particularly large delays between changes in driving forces and environmental impacts such as climate, developments have been considered for the next half century rather than for the next quarter century.
• The table depicts environmental impacts as changes towards the end of the causality chain: health impacts, biodiversity impacts and the like.
• The table highlights differences and similarities between regional impacts. In addition, a ‘world’ column has been included to provide an overview of the impacts on a global scale. For some issues, such as climate change, the outcome of the model based analysis directly shows a relevant impact on the world as a whole.
• For other issues, such as for population living in areas with water stress, the signal in the ‘world’ column is a weighted average of the regional signals.
• For biodiversity, the remaining mean species abundance was considered rather than the decrease. Considering the decreases would not have differentiated between the cases that were investigated, partly because of the inertia of the natural system.
• For urban air pollution, the modelled health impacts up to 2030 were considered, as reported in Section 2.1.5.2. In order to differentiate in BRIC and the Rest of the World, the  trends in 2030-2050 in emissions of sulphur and nitrogen oxides were weighted in.
• Generally, a red signal shows an increase of a large problem in the context of internationally articulated objectives. An amber signal shows either improvement or deterioration of the problem, and a green signal reveals a significant decrease in the problem.       

• Back to OECD Environmental Outlook: Regional results.