If you say, "No WAY!" then join the club!
And THAT is exactly the point! THERE ARE NO HARD-AND-FAST RULES FOR FIGURING OUT WHETHER YOU ARE IN A SITUATION OF UNCERTAINTY!
What I hope you learn from this Self-Study Guide is that:
** If the warning time of approaching vehicles is less than your crossing time, YOU ARE IN A SITUATION OF UNCERTAINTY, because you can never be sure whether you have a gap in traffic long enough to cross. ** That is why it is so important that YOUR STUDENTS ARE ABLE TO COMPARE THE WARNING TIMES OF APPROACHING VEHICLES WITH THEIR CROSSING TIME. |
Hey, maybe it will help if I share some examples from the Uncertainty Prediction Challenge to show that you can't predict Situations of Uncertainty based just on features of the street, or speed of traffic, etc.
#1.
#2. 
#3. 
#4. 
Does a sharp bend mean it's a Situation of Uncertainty?
- Photo #1 above -- a sharp bend in the road nearby DOES make a Situation of Uncertainty (we can not hear traffic beyond the bend).
- Photo #2 above -- a sharp bend in the road nearby DOES NOT make a Situation of Uncertainty (we can hear traffic from far beyond the bend - see video below).
- Photo #1 above -- the traffic is slow but there IS a Situation of Uncertainty
- Photo #2 above -- the traffic is fast but there IS NOT a Situation of Uncertainty
- Sometimes conditions can change, so that at one time, whenever it's quiet you can hear the vehicles with enough warning, but that's not true at another time. For example:
- When the roads are wet, traffic can be heard better than when they are dry.
- Installing a speed hump at the street in photo #4 above made it possible to hear the traffic with enough warning whenever it is
quiet.
- Later in this Section you'll learn that at the crossing where Gordon Parks was killed, there was a Situation of Uncertainty during the day but not in the evening.
- At the street in photo #3 above, parked vehicles created a Situation of Uncertainty because they blocked the sound of traffic.
And yet in our research, when we placed a barrier between blind participants and the traffic (as shown in the picture to the right), it didn't seem to impair their ability to hear the vehicles much (Wall Emerson & Sauerburger, 2008).
So the presence of something that might block the sounds is not a reliable indicator as to whether there is a Situation of Uncertainty either.
- Here are two examples showing you how unreliable any rules are for determining if we're in a Situation of Uncertainty.
The first video shows a crossing with a sharp bend to the right, and it is NOT a Situation of Uncertainty!
The next videos show a street that is straight, with no hills or bends, and yet we can't hear the approaching vehicles with enough warning!
NOTE: The links to the YouTube videos below may not be accessible from restricted sites or on certain browsers.
Situation of Confidence with a sharp bend in the road to the right
- The video to the right was taken in front of my community, where we can hear the approaching vehicles long before we see them. I analyzed the approach of more than 30 vehicles from each directions, and heard them all with enough warning.
In the second video [right, below] Rikilynn describes the situation and shows the street, which is very straight in both directions with no trees or other obstructions. The cars that we hear are all coming from the left.