This study determined the nature of relationship between the volume of CO2 liberated per passenger kilometre travelled by Public Service Vehicles (PSVs) that have large carrying capacity and those that have low carrying capacity in Kisumu City using observation with a view of reducing the amount of CO2 liberated by PSVs (matatus). The study particularly sought to reduce the emission of CO2 into the atmosphere as a result of burning fossil fuel. The study was conceived as a result of the uncontrolled thriving and congestion of the 14-seater public service vehicles commonly called “Nissan Matatu” in Kenya. Over the years, transport pooling has been seen in the light of economizing fuel usage. Due to the global increase in the number of motor vehicles in urban setting, pooling shifted and was seen as a strategy to reduce congestion. The burning of fossil fuels releases CO2 which is a greenhouse gas into the atmosphere. This study sought to quantify the extent of fuel consumption in relation to the seating capacity of the PSV by determining on the average the quantities of fuel burnt by different capacities of the PSVs. Pearson Product-Moment correlation coefficient showed a relationship of -.917 between the volumes of CO2 liberated per passenger kilometre travelled in large carrying capacity and low carrying capacity passenger transportation. This study concluded that the 14-seater PSVs emit twice as much volume of CO2 as the pooled PSVs and recommended the implementation of policies aimed at reducing the usage of the 14-seater PSVs.