Ground vehicle mobility in soft soil is crucial to many military missions. Thus, it has been tested and quantified in a metric called Vehicle Cone Index (VCI) since World War II. VCI provides an index of the minimum soil strength necessary for vehicle mobility. The standard operating procedure for VCI field testing and data analysis is detailed herein. Also, a new method for quantifying VCI uncertainty has been proposed, which uses confidence bounds on mean measurements of soil strength. A sample analysis of actual field data is provided.