In recent years, a number of different Blind Spot Monitor (BSM) systems have become more and more popular in North American automotive market. The BSM system advises the driver of vehicles travelling in adjacent lanes when these vehicles are also in the driver's outside rearview mirror blind spots.Similarly, when the vehicle is backing up from a parking spot, cross-traffic vehicles can be in the driver's outside mirror blind spots. In this situation, the Rear Cross Traffic Alert (RCTA) system alerts the driver when the driver shifts the vehicle in the reverse gear and there are approaching cross-traffic vehicles. The benefits of RCTA system was presented by .The RCTA alert studied in this paper is given by playing an audible sound and by flashing the outside mirror indicators. The RCTA and BSM systems share the same vehicle sensors and most of their vehicle components.The work presented in this paper researches a new method to properly identify the RCTA alert timing in North America where the rate of front-in parking is higher than other regions and the parking lots are larger than in other regions allowing for larger cross-traffic speeds (typically from 5mph to 18mph). Therefore, North American customers are more likely to experience a situation that would activate the RCTA system during backup maneuvers. The drivers need the proper alert timing to respond to the different cross-traffic speeds. The method proposed in this paper alerts the driver when the RCTA system predicts that a cross-traffic vehicle will pass behind the driver's vehicle within a given Estimated Crossing Time (ECT).