Transponder for the blind?

Is there some way to incorporate a transponder within a car, so that a blind person can wear a device that sends out a constant beacon to which a device in the vehicle responds, alerting a blind person to the vehicle's proximity (slow pulses for far away, quick pulses for close up)?

I would really like it if the cars remained silent, while the blind are kept safe. Ultimately, drivers and pedestrians will adapt to the new situation, depending on their eyes and not their ears for their safety.