InfraSee: An Unobtrusive Alertness System for Pedestrian Mobile Phone Users

It is well recognized that walking while using mobile phones will make people more susceptible at various risks. Existing works to improve smartphone users' safety are mainly limited to detecting incoming vehicles. They are not able to address some more common and equally dangerous accidents such as trips, falling from stairs, platforms, or falling into an open manhole. These hazards are generally caused by a sudden change of ground. In this paper, we propose InfraSee, a system that is able to detect sudden change of ground for pedestrian mobile phone users. InfraSee augments smartphones with a small infrared sensor which measures the distance of the ground surface from the sensor. The temporal variation of distance can provide information about the change of ground surface ahead. InfraSee also leverages the information of smartphone sensors to improve detection accuracy, to reduce energy consumption, and to avoid unnecessary alarms. We have carried out extensive experiments in different scenarios and by different users. The results show that InfraSee is able to reliably detect about 80 percent change of ground surfaces. In addition, InfraSee can reliably identify the awareness of smartphone users and reduce unnecessary alarms.