This study centers on curbing carbon emissions from heavy duty trucks (HDT) in operation.A compact Temperature Swing Adsorption (TSA) CO2 capture unit, powered by engine waste heat, is designed.The unit, featuring two parallel adsorption chambers for alternating adsorption and desorption, is tailored to HDT space limits with a three-folded double-layer pipe structure, measuring 860 mm x 800 mm x 600 mm.Using zeolite 13X-APG mol. sieve as a CO2 adsorbent and referencing common internal combustion engine parameters, simulations were performed at an intake temperature of 323.95 °C, a target adsorbent temperature during heating stage of 90 °C, and an exhaust gas mass flow rate of 0.2354 kg/s, with the exhaust gas composition assumed to be 75 % N2 and 15 % CO2.The results showed that it can process 20 % of HDT exhaust gas, attaining around 86.11 % CO2 recovery and 93.8 % purity.Addnl., a Vehicle Energy Efficiency Design Index (VEEDI) is proposed to gauge CO2 emissions across vehicle types.VEEDI encompasses CO2 emissions, transport workload, and factors like weather and energy efficiency technologies.It also accounts for the CO2 capture unit′s impact.Case calculations indicate that the CO2 capture unit can reduce VEEDI from 82.49 to 69.29, underscoring the Mobile Carbon Capture (MCC) technol.′s emission reduction potential.Amid stringent CO2 reduction policies, VEEDI can guide vehicle design and certification, offering a reference for vehicle environmental performance during operation and a quantifiable metric for emission reduction effects.