Speed is a major risk factor in overall road safety performance. The objective of this study was to identify the most frequent explanatory variables and measures used to investigate the speed factor contribution to crash injury risk (CIR). For this purpose, a literature oriented approach was used. The analysis review, underpinned by data collected from 64 journal publications reported over the past 21 years shows that speed limit was the most frequently used variable selected by the authors to investigate speed contribution CIR. Following, speed delta-V was the second most used variable, despite the barriers to access in-depth crash quality data. Even so, the speed limit was used 3.5 times more than delta-V, possibly due to the facilitate accessibility to the roads standardize posted speed limits. However, it is unknown how much vehicles travel speed could deviate from the posted speed limit at the moment of the crash.