Impatience on Busy Roads - Not a Good Idea

Date & Time of Event: 17 October 2018 at 12h58 Where: Main Road, Kirstenhof, Cape Town between Honeywell & Military Roads On two occasions at the above venue, the driver of the Truck with Pick 'n Pay printed on the Load Body, sounded the truck's horn. I'd be very grateful to know the reason why? I was not aware of any form of emergency on the road. The only conclusion I can draw is that the driver has an extreme lack of patience. I draw this conclusion because at both times I heard the horn, I was giving way to other road users, either to enter Main Road or to make right turns across Main Road. I consider such actions good manners. After all, the traffic light at Military Road intersection was red. Neither that truck or myself would have crossed Military Road any sooner had I not given way for the other road users. What about the Golden Ruler - "Do unto other as you would like done unto yourself". I am also a truck driver and whether I am driving my own car like today or driving my boss's truck, I am always very grateful to any fellow road user who gives way and allows me safe entry from a minor road onto such a major and busy road as Main Road is.