Internal Evaluator: An internal evaluator is a member of staff who evaluates interventions delivered by the same organisation that they are employed by. To reduce bias it is better if the internal evaluator is not directly involved in delivering the intervention. External Evaluator: An external evaluator is an independent consultant commissioned to undertake the evaluation. They are independent of the organisation and can often provide a new perspective. Evidence-informed Practice: Evidence-informed practice refers to the systematic use of research and evaluation data to inform decision making on the road safety issues to be tackled, and on the most effective ways to address those issues. This takes place before the intervention has been chosen, designed and delivered. Evidence-informed?practice accepts that other types of (non-research) data can also influence decision making, such as: Political Imperatives, Public Opinion, and Professional Wisdom