Emission inventories are a detailed survey of pollutant emissions from different sources. They provide important information for city-planners, health, climate studies, among others. Most softwares that perform this task is not open source and few software implementations are based on a bottom-up approach. We propose an open source model that delivers emissions data with spatial and temporal segregation. This paper describes the methodology of a new R package for high resolution bottom-up vehicular emissions inventories, named VEIN.
			
			%Method:
			The VEIN model reads, distributes by age of use, extrapolates hourly traffic data 
			and estimates of hourly average speeds.
			 The model reads streets as vectorial lines using the \textbf{sp} package and includes several constructor classes. Each class has units from the \textbf{units} package. Emissions estimations are at street and hourly level. The type of emissions covered are: exhaust (hot and cold), deterioration, evaporative, wear and resuspension. It performs speciation and also incorporates functions to generate and spatially allocate emissions databases. This model allows users to load their own emissions factors. Furthermore, the model provides emissions factors from Copert, EPA and Brazilian databases.  The paper shows the estimation of CO for a traffic simulation in the western area of São Paulo City, Brazil. This paper also provides instructional examples for the VEIN package. 	
            
 			The model provides a new and fast way of elaborating and analyzing vehicular emissions inventories. The output of the model can also be incorporated in high resolution air quality models.
            Future versions of VEIN will include additional emissions factor options for other countries/territories.