Research -- are there really Situations of Uncertainty and Situations of Confidence?

In 2006, Dr. Rob Wall Emerson from Western Michigan University and I asked 22 blind people with normal hearing to sit in my mother's lawnchairs at 3 different sites, and raise their hand when they heard something that they thought might be a vehicle approaching them.

We studied primarily 4 things:

Detection-to-arrive time -- how many seconds passed from when one of the subjects first heard a vehicle until the vehicle arrived?
Level of ambient sound -- when the subjects heard the vehicle, was there any masking noise and if so, how loud was it?
Speed of vehicles -- how fast was the vehicle coming?
Sound level of vehicles -- how loud was the vehicle when it passed?

The sites we chose to study (pictured below) were all two-lane, quiet intersections with a speed limit of 25 mph (I'll explain later what I mean by "quiet intersections").

We are looking to the left along a straight two-lane street with a curb and grass on both sides, houses on the right side and woods on the left. A woman is sitting in a lawnchair on the grass about 4 feet from the left curb, facing the street. A few feet beside her is a grey board suspended on two poles. The board is 8 feet wide, the top is 5 feet above the ground, the bottom is about 3 feet above the ground, so that the board is beside the woman's head and shoulders.

Photo shows the same street looking to the right -- it is straight for about 2 block-lengths. On the left is an entrance into a housing development, on the right are trees and grass.

Site 1 was a street that is straight and clear of obstructions for at least a block in each direction, so the vehicles approached in what we called the "straight" approaches.

On half the trials at this site, we put up a barrier to block the sound (the "baffle" approach).

We are looking to the left along a two-lane street with curbs, grass and trees on both sides. The road is going slightly downhill and curves gently to the left, disappearing about 100 feet away. About 20 feet from us is the corner of another street. A tripod about 2 feet high and some equipment lie on the grass.

We are looking to the left along a two-lane street with curbs, grass and trees on both sides. The road is going slightly downhill and curves gently to the left, disappearing about 100 feet away. About 20 feet from us is the corner of another street. A tripod about 2 feet high and some equipment lie on the grass.

Photo shows the same street looking to the right. It is lined with trees on both sides and houses on the left. The road is going slightly uphill and disappears about 200 feet away.

Site 2 was the same crossing that Linda Sussman showed me and that you saw in the video on page 7. The street has a severe bend to the right (the "severe bend" approach)
and a minor bend to the left (the "minor bend" approach).

We are looking to the left along a two-lane street with curb, grass and sidewalk on the left and thick trees on the other side of the sidewalk. On the right side are thick trees starting at the edge of the street. The road is going slightly downhill and curves gently to the left, disappearing behind the trees about 100 feet away.

We are looking to the left along a two-lane street with curb, grass and sidewalk on the left and thick trees on the other side of the sidewalk. On the right side are thick trees starting at the edge of the street. The road is going slightly downhill and curves gently to the left, disappearing behind the trees about 100 feet away.

Photo shows the same street looking to the right. We are standing on the corner of another street, and the main street continues slightly uphill and crests about 50 feet away and disappears down the other side of the hill.

Site 3 had a steep hill to the right (the "hill" approach)
and trees to the left (the "trees" approach).

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