This project will develop an open standard for heavy-duty fuel-cell modules in terms of size, interfaces, control and test protocols, with the objective of kickstarting the use of fuel cells and hydrogen in the heavy-duty mobility sector, where electrification with batteries is impractical. Multiple modules may be integrated in a system, similar to AA batteries; this will allow using the same modules for multiple sizes. Combined with the standardisation across several sectors (road, offroad, rail, maritime, etc.) represented by participating OEMs, the same modules will address a large pooled market. The size of the market, and the availability of multiple module suppliers (8 in this project alone) will create a fair competition environment where OEMs may choose and change vendors, driving down prices and activating a virtuous cycle through economies of scale and achieving one of the main goals of the FCH JU's Work Programme in the heavy-duty mobility sector. This project will also produce prototypes form 8 leading FC vendors, which will then be thoroughly tested by two independent institutes for compliance with the open standards produced by the project itself. The project will feature significant dissemination and outreach activities, especially towards external OEMs that may become customers of the module suppliers.