en عمومى General پژوهشي Research <div style="text-align: justify;"><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,serif">Global warming is being accelerated by rising greenhouse gas emissions from human activity, which carries serious repercussions for long-term sustainability. Of these gases, carbon dioxide (CO₂) is the most critical driver of climate change. Railway construction and maintenance, in particular, demand vast quantities of materials, making the sector a notable source of CO₂. To address this, we must implement thorough quantitative assessments and innovative design improvements to lower the industry&#39;s environmental cost. This study identifies and quantifies the carbon footprint of two common railway superstructures: ballasted track and slab track. To achieve this aim, a life-cycle assessment was performed in accordance with sustainable design and resilient infrastructure frameworks. Finally, the results were benchmarked against the Carbon Emission Index (CEI) to measure each alternative&#39;s deviation from the optimal reference value. The results of this study show that slab track produces higher CO₂ emissions than ballasted track, mainly because of its greater consumption of concrete and reinforcing steel. The total emissions were estimated at 823.87 t CO₂/km for slab track and 498.51 t CO₂/km for ballasted track. The CEI values of 1.62 for slab track and 1.55 for ballasted track further confirm that ballasted track demonstrates better environmental perfor&shy;mance. Therefore, from a carbon-emission perspective, ballasted track ap&shy;pears to be the more sustainable railway superstructure.</span></span></span></div> Railway Superstructure, Carbon-foot print, Carbon emission, Ballasted and slab tracks, Sustainable design 1 11 http://ijrare.iust.ac.ir/browse.php?a_code=A-10-247-3&slc_lang=en&sid=1 Hamidreza Heydari h_heydari@iust.ac.ir 180031947532846003059 180031947532846003059 Yes School of Railway Engineering, Iran University of Science and Technology Sara Tahanzedeh sara_tahanzadeh@rail.iust.ac.ir 180031947532846003060 180031947532846003060 No School of Railway Engineering, Iran University of Science and Technology