BOX 2: Timing Method for Assessing the Speed and Distance of Vehicles
- Define an arbitrary length of time ("X" seconds), which is typically one or two seconds longer than the time needed to cross an entire street (for analyzing traffic from the right) or half the street (for analyzing traffic from the left).
- Stand at the curb and, as vehicles approach, try to judge by their speed and distance when they are X seconds away.
Start a stopwatch when you think that a gien vehicle will reach you in X seconds.
- Stop the watch when the vehicle reaches you. If the lapsed time is signicantly longer or shorter than X seconds, you did not accurately perceive or judge the vehicle's speed, distance, or both.
Use this feedback to modify when you start the timer the next time.
- Continue to judge the cars as in Steps 2-3, with the goal of improving your judgment until you can discern when the vehicles, regardless of their speed, are approximately X seconds away from you.
That is, you will start the stopwatch for faster vehicles when they are farther from you than you will for slower vehicles, which you will allow to approach closer before you start the stopwatch.
If your judgment does not improve, perhaps you are unable to perceive the speed and distance of vehicles accurately because of impaired depth perception or acuity and should consider alternatives to determine when there is enough of a clearance in approaching vehicles to start crossing.