A crash modification factor (CMF) is a factor used to compute the expected number of crashes after implementing a given countermeasure at a specific site. It is defined as the ratio of expected crash frequency with improvement over that without improvement. The CMF Clearinghouse contains a web-based database of CMFs along with supporting documentation to help transportation engineers identify the most appropriate countermeasure for their safety needs. The CMF Clearinghouse compiles documented CMFs in a central location and provides a searchable database that can be easily queried to identify CMFs to meet a user's needs. Using the site, you can search to find CMFs or submit your own CMFs to be included in the clearinghouse. The CMF Clearinghouse is maintained by the UNC Highway Safety Research Center with funding from the Federal Highway Administration.