The most commonly used empirical approach to address issues of attention constraint is evaluate the degree of interference in dual or multiple tasks. The purpose of this study was designing software to estimate the relative interference between multiple tasks and determine its validity in performance prediction of simultaneous multiple tasks. in order to assess the validity of software, 46 students with a driving certificate from East Tehran branch of Islamic Azad University were selected by available sampling method, the response time to the visual and auditory stimulus of participants during driving in different conditions was measured by using software and hardware installed on their cars, and then relative interference in the above mentioned conditions was estimated by using relative interference software. The result of pearson correlation analysis showed that there is a high, meaningful and direct correlation between the amount of estimated relative interference with the software and measured participantschr('39') response time in different driving conditions (r=0.95, p≤0.01). Therefore, the designed software can be used to predict the amount of interference between two or more simultaneous tasks.