BOX 1: Timing Method for Assessing the Detection of Vehicles Determine the time needed to cross either by estimating your walking speed and the width of the street or by timing several crossings and using the longest time (do not use the average time, since you are looking for the worst-case scenario). While standing at the curb, wait until no approaching vehicles are detected (a perceived lull in traffic). Start a stopwatch when you see or hear something that might be an approaching vehicle. Stop the stopwatch when the approaching vehicles passes in front of you. If the time recorded is less time than you need to cross, the vehicle would have reached you before you finished crossing if you had started to cross just before you detected it. If the recorded time is longer than your crossing time, you would have completed the crossing safetly if you had started before it was detected. Continue timing the detection of approaching vehicles until sufficient samples have been taken to conclude whether you can detect vehicles well enough to know when it is safet to cross. If you started the timer the instant you first detected anything that might have been a vehicle, yet one reached you in less time than you need to cross, you cannot detect vehicles sufficiently under this condition, and you should consider alternatives or be aware that if you cross at this spot, you are depending on drivers to see and avoid you.

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.