to determine when it is "clear to cross"
Be able to determine when it is quiet enough to be "all clear" (understand the effect of masking sounds)
Is this skill really necessary?
The importance of understanding the effect of masking sounds hit me like a ton of bricks when I went back to analyze the crossing where Sue Etters was hit.
I had assumed that Sue had been crossing in a Situation of Uncertainty because she said she crossed only when it was quiet, and yet she was often surprised by vehicles that she hadn't heard when she started crossing.
When I was finally able to assess the situation, I was shocked to find that it was NOT a Situation of Uncertainty, even when the road was dry and it was 4:00 in the afternoon (when the sound level of "quiet" is usually highest)!
So what's going on here?
If this was not a Situation of Uncertainty, why was Sue often surprised and eventually hit by a car she hadn't heard when she started crossing?
Well, to make a long story short, I found out that when Sue thought it was "quiet," there were actually still some masking sounds from receding cars.
And I had noticed that her crossing was one of those places that I told you about, where even the slightest masking sound, such as receding cars after they were out of sight, or a train in the distance, kept me from hearing vehicles with enough warning.
So Sue didn't realize how quiet it had to be.
She hadn't noticed that the sound of the distant cars made her unable to hear the sound of the approaching cars until it was too late.
That is why it's important for your students to understand the effect of masking sounds and, in situations where they can be confident that "it's clear to cross when quiet," they need to know how quiet it has to be in order for that strategy to be effective!