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White canes give the visually impaired the freedom to travel independently in unknown environments, but they cannot warn the user of overhead hazards such as tree branches. This paper presents the development and evaluation of a device that provides haptic cues to warn a visually impaired user of low-hanging obstacles during white cane navigation. The Haptic Alerts for Low-hanging Obstacles (HALO) system is a portable and affordable attachment to traditional white canes. By pairing distance data acquired from an ultrasonic range sensor with vibration feedback delivered by an eccentric mass motor, the device aims to alert users of low-hanging obstacles without interfering with the standard functionality of a white cane. We conducted a preliminary validation study wherein twelve blindfolded subjects navigated a custom obstacle course with and without vibration alerts from HALO. The results showed that this new device is intuitive and highly effective at enabling the user to safely navigate around low-hanging obstacles.