The all-way stop is the generalization of the four-way stop. There can be all-way
stops at intersections of 3 road segments, or at intersections of 5 or more (though
there are very few such intersections).
There is a stop sign at every entrance to the intersection, and usually a stop line
painted on the road as well. In most cases, in the U.S.A., there is a smaller
rectangular sign below the octagonal stop sign with the text "FOUR WAY STOP" or "ALL WAY
STOP". Quite often there are pedestrian crossings at all-way stops, simply because it is
a place where all cars should stop, under all circumstances, so it's a relatively safe place
for pedestrians to cross the road.
A vehicle approaching an all-way stop must slow and stop at the stop line. While
slowing down, the operator of the vehicle should be scanning the other road segments
connected to the intersection. If there is another vehicle between the driver (or cyclist)
and the intersection, he/she must not pass that vehicle, must wait for it to pass through
the intersection, and must stop at the stop line regardless. It is not permitted for one
vehicle to immediately follow another through the intersection.
Once at the stop line, the operator must assess the situation. If a vehicle is already
in the intersection, the operator must wait for that vehicle to exit. If another vehicle is
waiting to enter the intersection at the same time, the vehicle on the left must yield in
countries where cars drive on the right-hand side of the road, or the vehicle on the right
must yield in countries where cars drive on the left-hand side of the road.
There is a simple way to remember which car must yield in the case of the all-way stop.
Imagine a 4-way stop, where each road segment is 2 lanes, one lane in each direction.
Imagine driving on the right-hand side of the road. If you approach an intersection, and
there's a car stopped in the road to the right, imagine what would happen if you proceed:
you would pass directly in front of that car's front bumper. If the driver of that car were
careless or unobservant, and started moving, or if that car got crashed into from behind,
your car would very probably be hit on the side. Now imagine if there were a car
stopped on the road to the left: there is one lane-width between your path of travel and the
stop line that car is at. If the car took off suddenly, or were hit from behind, it would
have further to travel before hitting your car, more time for you or the other driver to
react, more chance of avoiding a collision or accident. Therefore, it is simply
safer for all involved if the car on the right were to proceed while the car on the
left waits.
Of course, there is a bit more to it than that. If driving on the right side of the
road, and making a right turn, the only chance of a collision is if another driver at the
intersection plans to exit on the same road. So it is safe to make a right turn at an
all-way stop even if there are other cars already in the intersection, as long as none of
the other cars are headed for the same exit.