This paper presents the results of a study on crash conditions and occupant characteristics in side impacts to support the development of advanced side impact test procedures. The US vehicle fleet has been changing in recent years with a growing population of light trucks and vans, and the rapid introduction of side impact inflatable restraints for both thoracic and head protection. The study utilizes the US NASS/CDS, and FARS and GES (1990-2001) to characterize the current and projected US side crash environment in order to identify opportunities to improve side impact protection for the modern US fleet.