PHOTO #1: You said "Yes"
-- GREAT! You are correct -- I timed my detection of 35 cars from this direction and was able to hear all of them with enough warning to know it's clear to cross that half of the street whenever it is quiet (click here if you want to read the observations).
PHOTO #5: You said "Yes"
OOPS -- you were wrong, but don't feel badly, I was fooled just like you were! (Click here if you want to read the story.)
Even though the traffic is visible for a long distance, for some strange reason it is not possible to hear them until they reach the bottom of the hill, and by that time some of them are too close and/or fast and would have to slow down to avoid hitting a pedestrian who started to cross when it was still quiet (just before the vehicle could be heard).
PHOTO #5: You said "No"
GREAT -- you were right! Hey, you did better than I did, I was fooled by this one (click here if you want to read the story).
Even though the traffic is visible for a long distance, for some strange reason it is not possible to hear them until they reach the bottom of the hill, and by that time some of them are too close and/or fast and would have to slow down to avoid hitting a pedestrian who started to cross when it was still quiet (just before the vehicle could be heard).
Oops -- wrong, but you were close!
As you suspected, the speed of each vehicle had very little effect on how well the subjects could hear it approaching (the detection-to-arrival time).
If you want to see the graph of the data you can click here.
The factor that had absolutely no relationship whatsoever to how well the subjects heard a vehicle approaching (the detection-to-arrival time) was:
how loud the vehicle itself was!
Yeah, it blew our minds, too.
You can click here if you want to see the graph of the data -- it's a total scatterplot showing no relationships whatsoever.
Correct! As the ambient noise level increased, it got harder and harder to hear the vehicles above the masking sounds, as you can see in the chart below (click here for a description of the chart).
Well, it makes sense, doesn't it? That's why people say to wait until it is quiet to cross.
Oops -- wrong, but you're very close!
The presence of a sharp bend in the road or a hill had a great effect on how well the subjects heard the vehicles approaching (the detection-to-arrival time), but it wasn't the most significant factor.
The factor that affected the subjects' ability to hear the vehicles approaching (the detection-to-arrival time) the MOST was
the level of ambient sound. This is probably not a surprise, if you think about it -- as the ambient noise level increases, it gets harder and harder to hear the vehicles above the masking sounds, as you can see in the chart below (click here for a description of the chart).
That's why people say to wait until it is quiet to cross.
. . . observe and analyze how well you can hear / see the traffic in THAT situation!
The only way to determine if you are in a situation of uncertainty for gap judgment is to
observe and analyze how well you can hear / see the traffic in THAT situation!
With this definition, it's easy to delineate whether something is "safe" or not -- if a person feels that its risks are acceptable, it's safe for that person, if not, it's not!
Of course, that means what is considered "safe" will be different from person to person, depending on each person's level of risk acceptance.
When you're ready to return to Section 3 -- click here.
No, but you're getting warm! "Reasonable" means "within the bounds of common sense" or "not extreme or excessive; fair."
If "common sense" had a clear delineation of how much risk is considered to be "safe" this definition would work.
But it doesn't, so this definition isn't functional either -- there is no way to determine the level of risk that would be considered "within the bounds of common sense."
No, you definitely could NOT use the "turn around" strategy here to avoid the possibility of a vehicle reaching you during your crossing --
you do not have enough warning to be confident it's clear to cross even half the street!
For example, if you started to cross and then heard a vehicle or a noise before you reached the middle, you might not even have enough time to return to the curb before that vehicle could reach you.
You need to have enough warning to be confident that you have enough time to cross at least half the street.
No, you could NOT use the "turn around" strategy here since in some cases you have NO warning of approaching vehicles, and you need to have enough warning to be confident that it's clear to cross at least half the street.
The purpose of this strategy is to help ensure that drivers cannot reach you during your crossing and in this case, they are sometimes already there in the crosswalk without your even being aware of them.
The street was two lanes, with a well-marked crosswalk with signs saying "Yield to peds in crosswalk." In the middle of the street there is a refuge island (about 3-4 feet wide) and the nearest lane is made more narrow by having the curb extend about four feet into the street, with posts and a planter on the extension.
In the first minute, 6 vehicles approached from the right, 1 from the left, and no pedestrians crossed.
In the second minute, 7 vehicles approached from each direction, and
one pedestrian came across from the other side of the street (before he had reached the curb, a driver to his left slowed down to wait, and the two drivers behind that one also waited).
another pedestrian with a dog crossed from our side of the street (as she got ready to cross, two cars in the nearest lane passed her from the left;
while she was still in the middle of the first lane, a driver to her right slowed down and waited till she reached his lane and crossed; after she was in the second lane, another driver from her left slowed down in the first lane behind her and almost stopped because a man was walking on the sidewalk near the crosswalk, although he didn't cross).
The street has about 3 narrow lanes plus a shoulder between us and the first lane, which is the only lane for traffic from the left. The second lane appears to be a turning lane and the third is the through lane for traffic from the right.
There are no sidewalks. Our side of the street has grass stretching about 10 feet from the curb to the trees, and across the street are some woods. To our left is the entrance to a small parking lot, there are no buildings in sight, no painted crosswalk, no pedestrians visible.
Traffic is going about 40 mph. From our left, the traffic appears over the top of a hill -- they reach us about 4-5 seconds after we see them. Traffic from the right can be seen several blocks away, they reach us about 15 seconds after we can see them.
In the two minutes of video, 8 vehicles pass from the right and 9 or 10 from the left.
The brick street is about 4 lanes wide plus a 4-foot divider in the middle. The painted crosswalk is about 10 feet wide and cuts through a divider in the middle of the street (it is about 4 feet square on each side of the crosswalk).
It has one-way traffic coming from the intersecting streets and roundabout to our right.
During the 3-minute video, 4 pairs of pedestrians and two single pedestrians crossed, and none of them ever had to wait (either before starting or during the crossing), the drivers all waited for them to cross. In fact, one couple who approached when a driver had been waiting for other pedestrians waved the driver on, and then crossed while the next driver waited.
During this same time, one driver passed the crosswalk on this side of the divider and 20 passed on the other side. Of those 20, 15 came straight from the roundabout and 5 turned into the crosswalk from a side street.
Because they were going so slowly (about 5-10 mph) and/or waiting for pedestrians, there were only two breaks when when there were no vehicles approaching the crosswalk or waiting (in each of these cases, there were only about 12 seconds between one vehicle in the crosswalk to the next).