Using HEARING or VISION -- Which is better to
Determine when it is "clear to cross"?
WHEW! You've made it through the pages that describe how to teach students to determine that they have enough time to cross,
either by crossing when it's "all clear" or by crossing even though they can see something approaching in the distance because they know they still have time to cross before it arrives.
Hang on, we're almost finished, we just need to talk about students who have both functional hearing and vision.
They need to realize that
- the process of using hearing to cross streets is vastly different from the process of using vision, and
- each has its advantages and disadvantages.
Process for detecting approaching vehicles using hearing:
Wait for quiet to detect the vehicles.
- can detect vehicles approaching in all directions at the same time;
- can often detect vehicles approaching from beyond hills and bends in the road and other obstacles (though the sound may be reduced).
Photo to the right shows a situation where hearing is much more effective than vision.
The approaching vehicles cannot be seen until they are 4-7 seconds away but they can be heard 7-18 seconds away (if you want to see the detection times, click here).
can not detect vehicles if there are masking sounds such as other vehicles receding, wind, etc.
Process for detecting approaching vehicles using vision:
Students may overestimate or underestimate the benefits of using vision or hearing because they don't know how to use them and don't understand their limitations.
Thus it is very important that they
Look in one direction until clear and then the other and back again, using whatever strategy is necessary to effectively glance or scan from one side to the other to be sure there is a crossable gap in both directions.
- can detect approaching vehicles even with loud noises and other vehicles nearby.
Photo to the right shows a situation where vision is more effective than hearing.
The approaching vehicles can be seen more than a block away but even when it is quiet, they cannot be heard until they get near the bottom of the hill.
- cannot detect vehicles approaching from beyond hills and bends in the road and other obstacles (including other vehicles);
- cannot detect vehicles in both directions at once -- while looking in one direction, vehicles may approach undetected from the other direction.
Because vision and hearing use very different processes, it is usually difficult to look for approaching vehicles in both directions as efficiently as possible while at the same time tuning into the sound of approaching vehicles and listening for them as efficiently as possible, and vice versa.
Travelers therefore usually need to decide in each crossing situation whether it would be best to maximize the use of their hearing or their vision to detect the vehicles.
These issues will be discussed on the next page.
- learn how to use each effectively for crossing streets;
- understand the advantages and limitations of each so they can recognize which would be best for a given situation; and
- recognize situations when neither their hearing nor their vision, even when used as effectively as possible, can detect the traffic well enough to know when it's clear to cross (Situations of Uncertainty).