<p>The rise in global greenhouse gas emissions and the escalation of climate warming have heightened the urgency to reduce CO₂ emissions from road traffic and enhance the photosynthetic carbon sequestration capacity of plants. This study focused on 19 commonly found plant species along the Xiaogan motorway in Hubei Province, conducting a comprehensive analysis of their physiological traits and the interplay between soil physical–chemical properties and their photosynthetic carbon fixation capacities. The findings revealed that the photosynthetic carbon fixation and oxygen release capabilities of these plant species vary significantly. Notably, <i>Zelkova serrata</i><i>, </i><i>Sapium sebiferum</i> (L.) <i>Roxb</i>, and <i>Osmanthus</i> species demonstrated superior carbon fixation and oxygen release capacities compared to other tree species. Specifically, the daily carbon fixation rates per unit land area ranged from 21.92 to 70.96&#xa0;g·m⁻²·d⁻¹, while the oxygen release rates varied from 15.94 to 51.61&#xa0;g·m⁻²·d⁻¹. <i>Sapium sebiferum (L.) Roxb</i> showed the highest daily net carbon fixation rate per unit land area. Analysis of plant traits and soil physical–chemical properties indicated that the leaf area index and the levels of available phosphorus and potassium in the soil significantly influence the photosynthetic carbon sequestration capacity of plants (<i>p</i> &lt; 0.01). This research aims to provide scientific insights for developing high carbon sink vegetation patterns in motorway areas and to support the sustainable development of motorway infrastructure and management.</p>