US Army researchers lead new NATO standard for vehicle mobility

The North Atlantic Treaty Organization has accepted the Next Generation NATO Reference Mobility Model (NRMM) and adopted it as a standard after more than seven years of development by a team led by the U.S. Army DEVCOM Ground Vehicle Systems Center.
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When military commanders must move their vehicles over unfamiliar terrain, few factors can frustrate the best-laid mobilization plans more than misunderstanding the ground over which those vehicles will move. Hard-packed clay or soft sand? gravel or turf? Will the wheels get stuck and formations mired in the mud? (Picture source: U.S. DoD)

Overall, the NATO committee consisted of more than 60 scientists, engineers, and technical experts from 16 NATO nations who were involved in the model development process. “This group is marching towards a capability that will allow NATO to ‘own the terrain’, much like night-vision devices allowed us to ‘own the night,’” said Alan Shaffer, former Director for the NATO Science & Technology Collaboration Support Office and former U.S. Deputy Under Secretary of Defense for Acquisition and Sustainment. “The potential operational payoff could be immense.”

When military commanders must move their vehicles over unfamiliar terrain, few factors can frustrate the best-laid mobilization plans more than misunderstanding the ground over which those vehicles will move. Hard-packed clay or soft sand? gravel or turf? Will the wheels get stuck and formations mired in the mud?

Since the 1970s, NATO has maintained a scientific model for terrain traversability called the NATO Reference Mobility Model. According to NATO, “NRMM is a simulation tool aimed at predicting the capability of a vehicle to move over specified terrain conditions.” NRMM, originally developed and validated by the Army’s Tank Automotive Research, Development and Engineering Center (TARDEC, now the Ground Vehicle Systems Center, GVSC) and the U.S. Army Engineer Research and Development Center (ERDC), relies upon empirical data, that is, information collected or sampled directly, to determine what types of vehicles can move over what types of terrain at what speed. As modern vehicles regularly differ from the model’s parameters, like suspension type, weight class, and vehicle control systems, that the NRMM was designed for, the value of the NRMM became limited.

“The legacy mobility model was flawed and prone to give incorrect guidance,” says Paramsothy Jayakumar, the Senior Technical Expert for Analytics at U.S. Army DEVCOM GVSC and co-leader of the NATO committee developing the new standard along with Michael McCullough of BAE. “We were concerned that NRMM wasn’t enhanced with high fidelity and would leave the NATO nations with an inferior mobility tool that could neither differentiate between competing vehicle designs nor accurately predict how well those vehicles could move across terrain under various operational scenarios.”

The Next Generation NATO Reference Mobility Model, or NG-NRMM, is a computational approach to modeling. Inputs to the model like vehicle type (weight, wheeled or tracked, number of axles, etc.), soil composition (boulders, sand, clay, or anything in between), and general terrain features produce a usable map of traversability. This map provides the driver (human or otherwise) with information about how fast the vehicle will be able to move, if at all, through that terrain.

The complex problem of representing this mix of variables into a reliable model, then verifying that model across a spectrum of terrain types with a broad array of vehicles, spanned more than six years, tying together the efforts of NATO scientists from across the alliance. “This model produces stochastic mobility maps: a graphical depiction of areas a vehicle can and cannot traverse that we call ‘go’ and ‘no-go’ areas alongside an estimate of that map’s reliability to account for uncertainties in the data. These maps are key for military leaders’ consideration of missions and the planning of those missions by the Warfighters,” says Jayakumar.

In addition to the mobility map, the approach includes computations for a vehicle’s “best path” from one point to another, providing additional tools to decision-makers quickly. These include data for a vehicle’s estimated best speed along with parts of the terrain, informing Warfighters of where areas are traversed quickly or slowly, or perhaps not at all.

The Next Generation NATO Reference Mobility Model is a computational, not empirical, one. That means that the interaction of different types of vehicles’ wheels or tracks with different types of soils is carefully computed and modeled, giving the NG-NRMM greater flexibility across a wider spectrum of vehicle types. The NG-NRMM is a high-fidelity, computational approach that shows how well a given vehicle can move over terrain, providing commanders and leaders quality, real-time information to inform on-the-ground operations. (Images from “Next-Generation NATO Reference Mobility Model (NG-NRMM) Development,” NATO Technical Report TR-AVT-248)

David Gorsich is the U.S. Army DEVCOM Chief Scientist for Ground Systems. He championed the effort, keeping the initiative going when team changes, resourcing, or other factors threatened to sideline it. “We established new NATO Standard recommendations on how to predict off-road mobility for operational planning as well as the acquisition of new ground systems,” said Gorsich. “This new method reduces prediction errors from 75.1% to 6.2% resulting in better equipment and operational plans, saving countless lives into the future. Why? Soldiers die when vehicles get immobilized and stuck. This doesn’t have to happen. We have not only led the U.S. but also our NATO allies making this capability a reality for the alliance.”

The process and technology requirements that the committee developed were documented as the recommended NATO standard, a standard that was accepted and adopted as, officially, NATO STANREC 4813 AMSP-06 Ed A Version 1. The standard becomes official July 16.

Bringing a new standard for mobility isn’t limited to the laboratories and computer labs, however. The committee conducted extensive benchmarking, or on-the-ground data collection tests. The benchmarking, including tests at the Nevada Automotive Test Center and Michigan Technological University’s Keweenaw Research Center (KRC), included a tracked, Armored Personnel Carrier, a wheeled Joint Light Tactical Vehicle demonstrator, and GVSC’s prototype Fuel Efficient Demonstrator- Alpha vehicle.

The researchers demonstrated how models for different vehicles and their interaction with the terrain were developed, how they integrated GIS-based terrain data into the new mobility model, how to map reliability was calculated from the data uncertainties, and more. “The old NRMM struggled with off-road terrains, which is where military mobility matters most,” said Jean Dasch, a principal scientist from Alion Science & Technology, a key contributor to the NATO committee. “The NG-NRMM is demonstrated to be in much better agreement with testing, predicts mobility for a much larger variety of soils, and was able to predict a mobility over a much greater diversity of automotive tests.”

Contributors to the effort came from beyond the U.S. Army DEVCOM’s Ground Vehicle Systems Center, to include the Army’s Data & Analysis Center, the U.S. Army Engineer Research and Development Center, and representatives from key industries and academia. Other NATO defense partners include Canada, the Czech Republic, Denmark, Estonia, Germany, Poland, Romania, South Africa, Turkey, and the United Kingdom.

One of the most important outputs from the Next Generation NATO Reference Mobility Model (NG-NRMM) is a data-rich, graphical, map-based representation of terrain types and how well, or poorly, a vehicle can traverse that terrain. In the left image, green-colored terrain represents terrain on which the sample vehicle can move quickly, while darker, redder-colored terrain is slower to traverse. On the right, the NG-NRMM computes a “best path” for vehicles traversing terrain. The NG-NRMM is a high-fidelity, computational model to show how well a given vehicle can move over terrain, providing commanders and leaders quality, real-time information to inform on-the-ground operations. (Images from “Cooperative Demonstration of Technology (CDT) for Next-Generation NATO Reference Mobility Model (NG-NRMM),” NATO Technical Memorandum TM-AVT-308) (Picture source: Douglas Halleaux, CCDC Ground Vehicle Systems Center)