Kenyan road transport currently accounts for about 78% of the total carbon emis¬sion in the country, a percentage that is lately and. steadily rising causing enormous scientific concern. Consequently, efficient road designs that support sustainable low carbon growth in certain road sections with embankments are required to help re¬duce the level of carbon concentration in modern roads such as Thika superhighway. This can be achieved by fitting suctions on walls of embankments to enhance forced convection. Highway pollution due to intense traffic jam poses high health risks to the people who stay in traffic jam for long hours due to accumulation of exhaust carbon cuiissious. It liad been proved by scientists that high carbon couccutratiou in road tunnels, embanked roads and underpasses form main contributor of various respiratory ailments for people trapped in traffic jam or trekking adjacent to roads for a long period of time. Significant mathematical analysis of this pollution prob¬lem on Kenyan roads had not been undertaken sufficiently in the past, but there is evidence that flow velocities and diffusion of vehicle pollutants is affected in roads with tunnels, embankments, interchanges and underpasses. Therefore, the purpose of this research was to develop a mathematical model, model airflow and carbon pollution in sections of roads with such structures and incorporate environmental awl 1110<ld input parameters to culiaucc forced couvcctiou in order to reduce carbon pollutants concentration in motorways. The methodology involved use of Godunov Finite Volume Method (GF\Tl\,l) to model and evaluate algebraically the governing equations of the flow in form of Partial Differential Equations(PDEs) with convec¬tive components. The findings were that forced convection more than the advection contribute largely to reduction of carbon particles concentration in embanked roads, road tunnels and underpasses.