The heavy-duty on-road sector is facing multiple regulations – CO2 targets (30% reduction by 2030 in Europe), NOx and particulate reductions (90% reductions in California), and electrification mandates (albeit very nascent, including only California’s Advanced Clean Trucks regulation). These could be met through a range of new technologies – improving conventional engines and emissions control to full electrification. But the solution will unlikely be a one-size-fits-all given the diversity of the applications. This is hopefully the first in a series of articles that examines the diversity of the HD sector, with the ultimate goal of outlining enablers and barriers for a transition to electrification (including fuel cell vehicles). We start with a US-centric approach simply because of relatively easier access to data, but it is noted that Europe and China will play a very important role and will be lookied at in the future.