I know I am late to this party but as a now retired environmental health officer you would not believe the serious nuisance reversing beepers caused, not just on construction sites but shop deliveries, factory sites where they are fitted to fork lifts etc. The stock a swerve from the company is that they are required by law, they are not! Also trucks fitted with them can switch them off. When reversing such vehicles in busy areas they maybe a help as are flashing/strobing lights, but at night the lights are better as they are readily seen. A particular problem can be night deliveries to shops, which are a thing in the UK. Nearby residents can get driven nearly mad by the beepers going of  between midnight and  5 am. There is a protocol now called silent approach which makes things much better other wise people like my self would require no noisy vehicle out side normal hours!