Design of an LED and Laser Diode Based Optical Vehicle Alerting System

The quiet operation of electric and hybrid vehicles at low speeds can pose a risk to pedestrians. To enhance pedestrian safety, Acoustic Vehicle Alerting Systems (AVAS) have been developed. The objective of this study is to develop an Optical Vehicle Alerting System (OVAS) that is integrated with vehicle speed data, with the aim of improving pedestrian awareness. By processing speed data transmitted via the Controller Area Network (CAN) bus, a variety of light patterns were projected on the road surface using optical sources in daylight conditions. In the pro-posed system, the efficacy of linear laser-based warning patterns generated by laser sources was compared with that of circular light patterns produced by arrays of light-emitting diodes (LEDs) com-bined with lens structures. A vehicle simulation was conducted to measure the light intensity and illumination profiles of laser and LED-based systems in a test environment. The findings revealed that an alerting pattern was generated with an illuminance of 90 lux at a distance of five metres when six LEDs with a wavelength of approximately 505 nm and an output power of 5 mW were employed. Similarly, a dynamic, speed-dependent linear alerting pattern was generated using three laser diodes operating at a wavelength of 532 nm and an output power of approximately 100 mW. The effectiveness of light intensity and illumination profiles was evaluated based on performance at different vehicle speeds. The OVAS system designed with LEDs was mounted at two different heights, 30 cm and 50 cm above the ground, and their performances were compared. It was observed that the OVAS positioned at 50 cm projected a light pattern covering 242% more area at a range of 1-3 metres compared to the system mounted at 30 cm. This emphasises the considerable impact of the installation height on the system's efficacy.