Aspects of the disclosure relate to detecting crosswalk using high-frequency transmitters. A mobile device may receive an ultrasonic signal indicating a location of the crosswalk from a signal transmitter. The mobile device may monitor a distance to the crosswalk based on the ultrasonic signal. The mobile device may generate an alert that the user is proximately located to the crosswalk after the user is in a predetermined vicinity of the crosswalk. The mobile device may update the alert to indicate a traffic pattern after the user has entered the crosswalk.