Intuitive understanding of crossing time at signalized intersections
    Photo shows a man standing on a corner facing a 4-lane street. To his left is a 6-lane street with a vehicle half-way through the intersection, going the same direction he's facing. Having an "intuitive understanding of crossing time" is helpful for learning skills and concepts for uncontrolled crossings, and the following story illustrates its usefulness for signalized crossings, too!

    A young man, "Timothy," was learning to cross at a typical signalized intersection, where Georgia Avenue is 6 lanes wide and Cameron Street is 4 lanes wide. He had enough vision to see the vehicles but not enough to see the traffic signal and walk sign.

    Timothy reached Cameron Street with Georgia Avenue on his left, as shown in the photo, and noticed that there was traffic moving in the nearest lanes of his parallel street. He started to cross, even though he didn't know how long that traffic had been moving. He figured if the vehicles on Georgia Avenue had enough time to cross Cameron, so did he! So we worked on his intuitive understanding of crossing time, and compared it to the crossing time of vehicles.

      Intuitive understanding of crossing time:
      I started by timing his crossing, which took him 8 seconds. I then asked him to imagine crossing the street, telling me when he started his imaginary crossing and when he thought he'd reach the other side. In the first trial, he thought he would have been across only five seconds after he said he started his imaginary crossing, but he got it correct on the second trial.

    Photo shows a man standing on a corner facing a 4-lane street. To his left is a 6-lane street with a vehicle just finished crossing the intersection. I should have continued working on his intuitive understanding of crossing time, but I went ahead and asked him to watch a vehicle that was on Georgia Avenue approaching Cameron Street, and imagine himself starting to cross Cameron when the car entered the intersection, then figure out where he would be by the time the vehicle got across the intersection. I timed the vehicle while he watched it cross Cameron Street.

    When the vehicle reached the other side of the intersection (where the white van is in the photo to the left), he said he would probably would have been about half or 3/4 of the way across the street if he had started when the vehicle entered the intersection. I told him the vehicle took 2 seconds to cross Cameron Street, so he would have been only a fourth of the way across (I think that if I had allowed him to develop a solid intuitive understanding of crossing time, he probably wouldn't have made that mistake.)

    I then had him observe a car beside him on Georgia Avenue go through the yellow light, and we saw that just a few seconds after it had crossed, the traffic on Cameron Street started moving. Again I asked where he'd be when the traffic on Cameron began moving if he had started to cross with that car, as he had done earlier when he saw traffic moving on Georgia Avenue. He said correctly that Cameron's traffic would have already been moving before he could have reached the middle of the street.

    He said that was scary, and he seemed to understand the risk of crossing when he didn't know how much time was left. He said the explanation with concrete illustrations helped make the point clear.

    Return to Self-Study Guide: Preparing Visually Impaired Students for Uncontrolled Crossings