Observational Studies : Often used to evaluate safety performance. There are two forms of observational studies: before-after studies and cross-sectional studies
The Organisation for Economic Co-operation and Development OECD (French: Organisation de coop ration et de developpement conomiques, OCDE), "Glossary", in Sharing Road Safety: Developing an International Framework for Crash Modification Functions (report serves as a guide to how research results can be shared internationally. It provides checklist for systematic review of road safety studies and a framework for standardising methodology), OECD Publishing, Paris, France 2012. http://www.keepeek.com/Digital-Asset-Management/oe cd/transport/sharing-road-safety/glossary_97892821 03760-12-en#page6, (Road Trfc and Transp Sfty - Brit) {604}