The Crash Modification Factor (CMF) Clearinghouse is a one-stop-shop for CMFs and related resources. This website was established in order to provide a regularly updated, online repository of CMFs. It serves as a search engine, which allows users to search for CMFs for a specific countermeasure. The CMF Clearinghouse summarizes published information on each CMF, including how it was developed (e.g., study design, sample size, and source of data) and what are its statistical properties (e.g., standard error). Where available, a link is provided to the publication from which the CMF was extracted. The CMFs are graded using a star quality rating based on five categories: study design, sample size, standard error, potential biases, and data source.