Horizontal coherence across objectives and measures can be evaluated between policies within the same policy area, such as between a policy on urban wastewater and wider EU water policy. It can also be evaluated between policies from different policy areas which may have to work together, such as between water policy and agricultural policy.

Policy landscapes at the EU and (sub)national levels are fragmented. Policies addressing specific sectors, activities or problems also often directly or indirectly affect other sectors and problems. As a result, various policies apply simultaneously to specific (sector) activities or (parts of) environmental problems.

An evaluation of horizontal coherence may help identifying excessive burdens, overlaps, gaps, inconsistencies, implementation problems, and/or obsolete measures. An evaluation may also help identifying potential synergies across policies and policy areas that could be strengthened. This can improve the overall performance of policies.

Vertical coherence may involve evaluating whether national policies are in line with the objectives of the European Green Deal, or whether certain national policies are consistent with the overarching environmental goals from the EU Climate Law, the proposed Nature Restoration Regulation, or the EU Directives. Vertical coherence can also be assessed at lower levels of governance, for example between municipality regulations and national policies.

In the EU, large parts of the policies (namely EU Directives) need to be transposed into national legislation. This means that states must incorporate the EU rules into national law. Even though states have some flexibility in the ways of incorporation, coherence towards the original directives should be ensured. After transposition, the policies become effective at the national level. To illustrate, the Water Framework Directive must be transposed into national law and implemented by producing river basin management plans that address water quality problems.