Mapping CO₂ traffic emissions within local climate zones in Helsinki

Road traffic is one of the major emitters of carbon dioxide (CO₂) to the atmosphere. Besides detailed carbon emission calculations, methods to upscale the emissions are needed, particularly in areas where good-quality data to calculate CO₂ emissions are lacking. To support this need, this study aims to quantify traffic-related CO₂ emissions within Local Climate Zones (LCZs) in Helsinki, Finland, and build a regression-based look-up table for the CO₂ emissions. To build the model, we use CO₂ emission data together with the variables, namely building surface area, asphalt surface area, population, traffic light, and road type. The median CO₂ emissions from the built LCZs are 1.8 times higher than those from land cover LCZs. The original classification of the LCZ framework is insufficient to describe traffic CO₂ emissions. The most critical variables in describing traffic CO₂ emissions are road type and asphalt area. We then build a generalized model applicable across LCZs, which can describe on average 55 % of the emissions. Based on the model, we introduce a look-up table for LCZ-specific traffic CO₂ emissions. This look-up table offers a practical solution for locations with limited resources to estimate traffic emissions. Crucially, this approach circumvents the need for traffic data, and minimizes computational resource requirements.