The section outside the graded portion, but within the designated RWS width is known as the flyover. It must be kept clear of fixed objects that project through a plane that starts at the edge of the graded area (the gable line) and extends upwards at 5%. It's purpose is not for the wayward ground movement of aircraft (that's what the graded part is for), but for protection of very low altitude manoeuvring adjacent to the RWY. For a Precision I, II, or III Runway with code number 3 or 4E only the area within 60m of the RWY centre line needs to be kept clear of mobile objects. The gable line is usually used as the reference, but this is actually outside this line. You can have transitory obstacles - vehicles etc - within the RWS as long as they are outside the 60m. As I said, mostly the gable line is used as this is easier.
There is an escape clause for the AD operator who cannot meet the RWS requirements. MOS139 Section 6.2.18.4 refers.