This section gives the reader an overview of the challenges related to dealing with the mobility and performance of vehicles in off-road conditions. It should be emphasized that the material of this section is important for both manned and unmanned vehicle applications. This is particularly relevant to the latter which operate in a wide range of severe terrains. The focus for such studies should be on the evaluation of the vehicle and operating environment as one interconnected system. Thus, a good understanding of soil mechanics is needed, as well as of the running gear of the vehicle.

The first part of the section is dedicated to the description of the indoor testing facility developed in the Advanced Vehicle Dynamics Laboratory (AVDL) at Virginia Tech. This test rig can be used with repeatable results to study the performance of pneumatic tires or rigid wheels on sand, soil, ice, or other type of surface. Illustrative examples from test studies performed on the rig on sandy loam and on ice are discussed. The second part of the section presents a study conducted at AVDL to compare the mobility, tractive performance, and energy efficiency of a robot in a wheeled and in a tracked configuration. The most significant results of this study are discussed.

It is not feasible to include in one section the state of the art in experimental terramechanics, tire and track modeling, and the challenges in assessing the mobility of robotic vehicles in off-road conditions. Dr. Sandu together with her students and collaborators performed significant research in all of these areas and others related in the last 15 years. The most significant publications that resulted from this work are included as references to this section. To ease the identification of studies dealing with a specific problem, the references were grouped as follows: The first group identifies publications resulted from Dr. Sandu's group in Experimental Terramechanics. As part of this group, [1–5] relate to Tire performance on ice, [6–8] relate to Tire performance on soil, [9–16] relate to Performance of robotic vehicles, and [17–19] relate to Test rigs design and modeling. The second group of publications is for Off-Road Vehicle Performance Modeling Studies. In this group, Tire modeling in off-road conditions occupies the largest section, [20–40], then Off-road vehicle performance modeling includes [41–45], Soil and terrain modeling is presented in [46–50], and Tracked vehicle performance in off-road conditions is included in [51–54]. The reader is encouraged to consult these references for a deep understanding of the experimental evaluation and mathematical modeling of the mobility, agility, and energy efficiency of manned and unmanned vehicles operating in unprepared conditions.