后面压五辆车的时候应该尽快靠右让行。
Question: When traveling in an area posted “Illegal to delay 5 or more vehicles,” am I obligated to pull over if I am traveling the speed limit and there is a string of cars behind me eager to go faster?

Answer: RCW 46.61.427 Slow-moving vehicle to pull off roadway — On a two-lane highway where passing is unsafe because of traffic in the opposite direction or other conditions, a slow moving vehicle, behind which five or more vehicles are formed in a line, shall turn off the roadway wherever sufficient area for a safe turn-out exists, in order to permit the vehicles following to proceed. As used in this section a slow moving vehicle is one which is proceeding at a rate of speed less than the normal flow of traffic at the particular time and place.

The last line in the RCW defines what the legislative intent was. It does not specifically say less than the speed limit, but “less than the normal flow of traffic at the particular time and place.”
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FROM 199.193.127.*