This invention involves a vascular access needle equipped with a fiber optic or piezoelectric sensing assembly. The :fiber optic or piezoelectric sensing elements are located at the distal end of the needle. The sensing elements may be bonded to the needle's outer or inner surface, or may be bonded on a separate stylet to be inserted into the core of the needle during operation. Vibrations and stress waves produced by arterial motions are detected by the strain sensing elements. In one embodiment, the magnitude of the signals produced by a sjngle sensing element is used to detect the presence of an artery as the needle approaches the artery. In another embodiment, two or more of the sensing elements cooperate to allow the real time estimation of the artery's location.