AASHTO OSOW-1, A Synthesis of Safety Implications of Commercial Vehicles Oversize/Overweight (December 2009), examines the safety implications of oversize and overweight commercial vehicles. The objective of the report is to identify known relationships between commercial vehicle safety and crash causation factors. The synthesis draws on literature resources and crash data identified with the help of an advisory panel of experts in heavy commercial vehicles. The resulting information can be used to support commercial vehicle enforcement and permitting practices. It can also justify expenditures and investments on size and weight enforcement to enhance safety. Enforcement staff, permitting officials, and safety program managers in highway agencies can use the synthesis when evaluating size and weight programs.