Observer Effect

The observer effect is when the act of observation changes what which is being observed. That probably sounds much snazzier in Latin. Yesterday we conducted our first ever bicycle and pedestrian traffic counts in Kirksville, MO. I was assigned the intersection of La Harpe and Boundary. The National Bike/Ped Documentation Project recommends conducting counts between 5 and 7 pm. The main thing we learned is that this time frame isn’t ideal for that location in July. We know that a lot of people run or bike on Boundary. But not between 5 and 7 pm when it is 90F!

The observer effect came into play during the second hour. To keep our first counts simple, we had decided to count only one hour, from 5 to 6 pm. I thought perhaps the bike/ped traffic might pick up later in the evening as it got cooler, so I elected to stay until 7 pm. The answer is, bike/ped traffic might pick up later as it gets cooler, but it wasn’t getting any cooler before 7 pm.

The other person doing the counts with me at that intersection couldn’t stay the extra hour so she left. On her bicycle. I dutifully counted her. I drank the last of my water. I realized my friend who lives down the street the other way would be getting home from doing her counts at another intersection in town. I called her and asked her to bring me some water. She biked to my intersection, and I dutifully counted her. She biked out, and I counted her again.

The total count was 5 bicyclists in 2 hours. One of those was an observer, and two of them were because I called for more water. Should I count it was only 2 cyclists? No, I reasoned, because if we hadn’t been conducting counts, we might have been out riding our bikes through that same intersection. By being observers, we are taking cyclists (ourselves) off the road.

In fact we plan to go for a ride tonight. After 7 pm, when we hope it might be a little cooler.

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