Comparing the NRMM (VCI), MMP and VLCI traction models

A military vehicle’s ability to traverse soft soil is a significant aspect of its performance. It is therefore important to be able to accurately predict and compare the soft soil performance of wheeled and tracked vehicles. The paper compares the vehicle cone index (VCI) model used in the NATO Reference Mobility Model (NRMM) with the mean maximum pressure (MMP) and vehicle limiting cone index (VLCI) models. The wheeled vehicle models compare reasonably well but the VLCI model for tracked vehicles indicates markedly higher limiting go/no-go soil strengths compared to the VCI and MMP models. Some of the relationships used in the VCI model appear rather irrational and could be significantly simplified. There is a considerable lack of reliable experimental data for tracked vehicles especially in the low traction region.