As an aid to the identification and analysis of carbon monoxide hot spot locations, the Intersection-Midblock Model (IMM) has been developed for the calculation of hourly carbon monoxide concentrations at user specified locations near streets or intersections. The IMM calculates carbon monoxide emissions due to vehicle cruising, acceleration-deceleration and idling by use of the EPA Modal Analysis Model. These emissions are then assigned to traffic links or portions of links based upon calculated intersection parameters such as cycle time, green time, queue length and delay time. After the emissions have been calculated and distributed among the individual lanes of each link, the EPA HIWAY Model is called to calculate carbon monoxide concentrations at each receptor location based upon input values of hourly wind speed, wind direction and atmospheric stability. If the street-building configuration, the wind speed and the atmospheric stability is such that a street canyon vortex will develop, the 'Street Canyon Model' is used to calculate the concentration of a street oriented receptor. This manual documents version 2 of the IMM (IMM-2). The principal changes from version 1 is the incorporation of the Motor Vehicle Emission Factors released in 1978 and the Modal Analysis Model coefficients and deterioration released in late 1977. Otherwise IMM-2 is substantially the same as the first version written by Victor Corbin and Michael T. Mills.