2. WAIT TILL QUIET/(CLEAR), THEN LISTEN/(WATCH) FOR APPROACHING VEHICLES:
While standing at the edge of the crossing, have the students wait until they can hear/(see) no approaching vehicles.
3. TIME THE DETECTION-TO-ARRIVAL ("warning time") OF A VEHICLE:
The students then listen or watch for traffic and report the first detection of something that MIGHT be an approaching vehicle.
They should not wait until they are sure it is a vehicle before they report hearing/(seeing) something that might be coming.
If they are using hearing, this should be when it is quiet or, if there is a steady noise that is considered part of the conditions of that situation, this should be when there are no extraneous noises that could mask the sound of the approaching vehicles.
Examples of steady noises that are part of the situation would be the sound of an air conditioner or a fountain, or a steady noise you are creating so the student can learn about the effect of masking sounds (this will be explained in Section 4).
- If they are using their hearing, they can report when they hear a vehicle approaching in either direction.
- If they are using their vision, they can only look in one direction at a time, so they will assess each direction separately.
First they watch and report their detection of vehicles in one direction until that assessment is complete, then they will turn and do the same for traffic coming from the other direction (strategies to glance efficiently from one side to the other to make sure it is clear in both directions will be covered in Section 4 -- for now, you are just assessing the situation in each direction, one at a time).
Start a stopwatch when the students first suspect that they hear/(see) something that might be an approaching vehicle.
Stop the watch when the approaching vehicle passes in front of the student.
If students report an approaching vehicle and there are none coming, praise them for reporting something suspicious, and reset the watch to wait for a vehicle.
4. COMPARE TO CROSSING TIME:
Compare the vehicle's detection-to-arrival time with the time the student needs to cross.
5. REPEAT TILL YOU CAN DRAW A CONCLUSION
If the time recorded for a vehicle's detection-to-arrival is...
- less than the students' crossing time, then that vehicle would have reached them if they had started to cross just before they heard/(saw) it. (YIKES!)
- more than the students' crossing time, they would have completed the crossing before that vehicle reached them, even if they had started just before they heard/(saw) it. (WHEW!)
You can draw a conclusion when you know whether or not the warning time of at least some vehicles was less than the crossing time.
That is, one of the following happens:
1. The detection-to-arrival time (warning time) of a vehicle is SHORTER than the student's crossing time even though
Hey, I already know what you're asking yourself!
Conclusion: The student is in a Situation of Uncertainty.
2. The full range of detection-to-arrival times for traffic coming from both directions is LONGER than the student's crossing time.
Conclusion: The student is in a Situation of Confidence.
How the heck can I be sure that I've measured the warning time of enough vehicles to know that the "full range of detection-to-arrival times" for traffic approaching from either direction is longer than the crossing time?
Yes, that is a HUGE issue which merits several pages to discuss!
The next page will start to address that issue.
Consideration when using the TMAD:
- Was it quiet when the vehicle was heard?
Sometimes when assessing situations for students who use hearing, a vehicle's detection-to-arrival time is less than the crossing time because when they first heard it, there was extraneous masking noise (perhaps unnoticed by the student).
In that case, you can't use the detection-to-arrival time of that vehicle to conclude it is a Situation of Uncertainty.
However, you can take the opportunity to make students aware of the presence of a masking sound and how it can reduce their ability to hear the vehicles (this will be covered in Section 4).
To find out if they can hear the traffic well enough whenever it is quiet, continue steps 2-4 while making sure that when the student reported hearing the vehicles, there were no extraneous masking sounds.