How do you know what are the shortest warning times for vehicles for a given situation?
As explained on the previous page, before you can conclude that a situation is a Situation of Confidence for traffic coming from one direction or the other,
Since you cannot conclude that you have a Situation of Confidence until you're sure you know what the shortest warning time for that situation is, how can you be sure you've included one of them when you analyzed the situation?
This is a very important question.
- you have to determine the full range of warning times (detection-to-arrival times) for those vehicles and
- the warning time of all vehicles in that range -- including the shortest warning time -- has to be longer than the student's crossing time.
(The vehicles with the shortest warning time, by the way, are NOT necessarily the fastest vehicles, or even the quietest ones -- click here if you want to know more).
Some people feel that because it is not possible to observe every vehicle that might ever pass in the future, we can never conclude that we have a Situation of Confidence -- every crossing should always be considered a Situation of Uncertainty (Bennett, 1991).
If this is a concern to you, you might want to read Considerations regarding the "Shortest Warning Time" in the range of vehicles.
Meanwhile, the next page has some suggestions for helping to ensure that even vehicles with the shortest detection-to-arrival times provide a warning that is long enough that you can be confident it is clear to cross.