No matter how safe and careful you drive, accident can happen due to other driver's mishap. This phenomenon is described as secondary accident. For example, recently the death of a lorry driver after a gantry fell on him following another accident involving a trailer and a car at the 445th kilometre of the North-South Expressway near Rawang.
As described by The Star Newspaper above, a Proton Wira hit the rear of a trailer causing the trailer to lose control and plough into the divider. The crash uprooted the support of a heavy signboard column, located in the highway median, causing the heavy signboard to fall onto an on-coming lorry travelling on the opposite lane of the highway. The lorry driver died in the accident and the lorry dragged the signboard for about 100 metres. The drivers of the trailer and his passenger only suffered minor injuries.
Thus, the incident started with the carelessness of the proton wira driver which causes the trailer to lost control of his trailer. Unfortunately, a heavy signboard gantry located at the incident eventually causes the death of an unfortunate lorry driver that happened to travel in the opposite direction at the same time.
In traffic engineering, the first principle that should be considered when designing high speed highway facilities is to remove any fixed objects from the road side. There should be a minimum distance provided for the fixed object to be placed and the base of the fixed object should be adequately protected from the on-coming traffic. In case that the fixed object is too close to the roadside, adequate protection system such as by providing guardrail (which is actually a roadside hazard if it is not being design properly) to prevent any out-of-control vehicles from hitting the object.