A pedestrian crosswalk, which is a traffic marking painted on a road surface, is a place designated for pedestrians to cross a road. A pedestrian crosswalk is often found at intersections or the middle sections of roads where many pedestrians cross. Today, as most of the pedestrian crosswalks, a zebra crossing having alternating dark and light stripes is used for reminding car drivers to give way to the pedestrians crossing the road. However, the use of such traffic markings is not enough for controlling and directing traffic in a place where the traffic volume of pedestrians and vehicles is high, and there are often accidents caused by pedestrians and vehicles struggling for smooth traffic on the same road. Therefore, traffic signals, also known as traffic lights, are also provided at the pedestrian crosswalk to control flows of traffic. However, such traffic signals only provide light signs for pedestrians to follow when crossing the road, but are unkindly for a visually impaired person.
In recent years, due to the society's concern for the safety of vulnerable groups, access-free facilities have also become a part of urban construction. Therefore, in order to provide an accessible environment for visually impaired persons in pedestrian crosswalks, audible traffic signals are also provided. The audible traffic signals, when changed to green, indicate a walking direction of pedestrians by producing different sounds to help visually impaired persons recognize the light signs for easily crossing the pedestrian crosswalk. However, although such audible traffic signals can produce different sounds to indicate different directions to guide visually impaired persons, the sounds are emitted in all directions and are easy to cause confusion, which makes the visually impaired persons unable to recognize the walking direction, and deviate from the walking direction when crossing, resulting in danger or accident. Furthermore, the visually impaired persons have to be trained to be able to recognize the directions represented by different sounds of the audible traffic signal, and it is very inconvenient for them. Moreover, in order for the visually impaired persons to clearly hear the sounds of the audible traffic signal, the sound volume must be greater than the ambient noise. However, such a sound volume is nothing but a noise that affects the lives of nearby residents and also causes them physical and mental harm after a long-term exposure.