| 摘要 |
<p>The road sign system 10 comprises: a sensor assembly 12 and a signal assembly 14. The sensor assembly is operable to measure an environmental property. The signal assembly comprises a display device 20 configured to display a determined output based on the measured environmental property. The signal assembly may include a proximity detector operable to detect the presence of, for example a vehicle 18, person or horse. There may be two sensors the results of which are compared and potential error is determined if a difference between the results is above a threshold value. There may be a hydrostatic sensor, ultrasonic sensors and sensors to determine the height of water or presence of ice. The system may use near field communication or a cellular connection to nearby devices.</p> |
