The semi-trailer vehicle is located far away of 15cm down-stream the inlet with a sedan car is trailing it .The length between your car and semi-trailer pick up truck is then assorted from 4cm to 28cm. The analysis is conducted at three rates of speed – 80kmph (22.22 m/s), 100kmph (27.77m/s) and 120kmph (33.33 m/s). The web move is the resultant of causes at entry and rear area of the automobile. The worthiness of net pull make with distance between vehicles has been obtained at the three velocities and the mandatory graph has been plotted. Through the graph the lowest move position or most effective slipstreaming distance has been found. The graph obtained is shown in the fig-3. Within the fig-3 as distance boosts from 4cm to 12cm, the pull force rises. But after 12cm the move on the automobile started to diminish. This is because of the fact that after 12cm the vortex at the front end of the automobile changes course. At distances significantly less than 12cm, the strong trailing vortices from the downstream rotate counter-top clockwise through before the automobile body. The low vortex upstream of the trailing vehicle lessens in proportions, thus minimizing the suction result, hence the bigger pull. After 12cm the course of vortex just before the automobile changes from anti-clockwise to clockwise. This reduces move or is named beneficial slipstreaming. The opposite case take place after 20cm. The clockwise rotating vortex that was preceding present just before the sedan now will not favor the automobile. The result of the vortex diminishes after 20cm and it generally does not affect the move forces on the automobile. Thus, the move force again starts off in-creasing. When the automobile moves from the vortex made by the semi-trailer vehicle, slipstreaming result is negligible, i.e. for those three rates of speed the vortices made by the semi-trailer pick up truck diminishes in power following the distance of 20cm. Hence, it is clear that the slipstreaming impact is more pronounced at smaller distance of parting. From the normal Fig-3, it could be seen that lowest pull occurs at 4cm. But on taking into consideration the safety factor it isn’t recommended to keep too brief distance at high rates of speed. So the perfect slipstream distance is considered as 20cm which corresponds to second least move. Further studies have been performed to comprehend the impact of slipstreaming at various rates of speed. The length has been looked after at 20cm, which is the critical distance, and the rate of the vehicles has been mixed. The probable final result is shown in Fig-4. In the graph we can recognize that the slipstreaming works more effectively at higher velocities of travel.