There is significant focus on sustainable development of the built environment. Previous studies on sustainable construction have focused primarily upon improving the energy efficiency of buildings during the operational phase, recycling/reuse of building materials, and minimizing wastes. The environmental performance of onsite construction processes is not currently measured or reported as an industry standard practice. Measurement of carbon emissions is one way to understand and improve the environmental performance of onsite construction processes. This study provides an estimation of carbon emissions for transportation in post-tensioned slab foundation construction. Data were collected from a concrete trade contractor and sub-trade contractors in the Greater Phoenix Arizona area. First, carbon emissions are quantified for a typical production home using regional average data. Second, the influence of material and equipment transportation on the relative contribution of trades toward total carbon emissions is quantified. Ready-mix concrete transportation is found to be one of the most significant components and accounts anywhere from 25% to 63% of the total carbon emissions. Third, what-if scenario analysis is presented to study the influence of floor slab size and the travel distance on carbon emissions based on ready-mix concrete supply. Finally, an example is presented to demonstrate the aggregate level impacts. © 2009 Taylor & Francis Group, LLC.