A vehicle access system comprising: at least two sets of receivers and transmitters, wherein each set of receiver and transmitter is configured to receive a type of wireless communication signal from a corresponding transmitter of a user device, and wherein the type of wireless communication signal received by a set of receiver and transmitter is different from that received by at least one other set of receiver and transmitter; a signal module (112/112a/112b) in communication with each set of receiver and transmitter, wherein each signal module (112/112a/112b) is configured to process the wireless communication signals received from a set of receiver and transmitter to determine an initial location of the user device relative to the vehicle; a localization module in communication with the signal modules, wherein the localization module is configured to determine a final location of the user device relative to the vehicle, based on the initial locations determined by the signal modules; a controller configured to lock or unlock a door of the vehicle based on the determined final location of the user device, characterized in that each set of receiver and transmitter configured to receive a type of wireless communication signal comprises: a first subset of receiver and transmitter configured to receive said type of wireless communication signal at a first predefined frequency range; and a second subset of receiver and transmitter configured to receive said type of wireless communication signal at a second predefined frequency range, and wherein the system is configured to selectively operate the first subset of receiver and transmitter or the second subset of receiver and transmitter based on a geographical location of the vehicle. at least two sets of receivers and transmitters, wherein each set of receiver and transmitter is configured to receive a type of wireless communication signal from a corresponding transmitter of a user device, and wherein the type of wireless communication signal received by a set of receiver and transmitter is different from that received by at least one other set of receiver and transmitter; a signal module (112/112a/112b) in communication with each set of receiver and transmitter, wherein each signal module (112/112a/112b) is configured to process the wireless communication signals received from a set of receiver and transmitter to determine an initial location of the user device relative to the vehicle; a localization module in communication with the signal modules, wherein the localization module is configured to determine a final location of the user device relative to the vehicle, based on the initial locations determined by the signal modules; a controller configured to lock or unlock a door of the vehicle based on the determined final location of the user device, characterized in that each set of receiver and transmitter configured to receive a type of wireless communication signal comprises: a first subset of receiver and transmitter configured to receive said type of wireless communication signal at a first predefined frequency range; and a second subset of receiver and transmitter configured to receive said type of wireless communication signal at a second predefined frequency range, and wherein the system is configured to selectively operate the first subset of receiver and transmitter or the second subset of receiver and transmitter based on a geographical location of the vehicle. a first subset of receiver and transmitter configured to receive said type of wireless communication signal at a first predefined frequency range; and a second subset of receiver and transmitter configured to receive said type of wireless communication signal at a second predefined frequency range, and wherein the system is configured to selectively operate the first subset of receiver and transmitter or the second subset of receiver and transmitter based on a geographical location of the vehicle.