Abstract: It can shed bright light on the design and installation of urban road traffic signs to reveal the pattern of drivers' memory for traffic sign information changes over time and build the fading pattern of drivers' short-term memory. Power function curve is identified as the fading pattern of drivers' short-term memory for traffic signs. With the psychological theory of memory in mind, taking a test-car survey along a road segment installed with traffic signs as an example, the authors investigate how the amount of traffic sign information impacts drivers' short memory, how it changes over time, and builds the fading pattern of drivers' short-term memory. One of the findings shows that the Hermann Ebbinghaus Forgetting Curve is a good fit of the pattern that drivers' short memory of traffic sign information fades over time.