Greater Greater Washington


What if we counted people like we count vehicles?

Of all of the disparities between different transportation modes, one of the most important and least talked about is the disparity of information. Right now in American cities we have an enormous and expanding set of knowledge about how cars and trucks move, yet we know almost nothing quantitatively about how pedestrians and bicyclists use the infrastructure.

Traffic camera. Photo by brewbooks.

Cameras and in-ground road sensors are placed in strategic locations along roadways, constantly streaming to gather very rich data on vehicular traffic patterns. Here are all of DC's. The data is processed and collected to, among other things, make future projections. Eventually a decision-maker, perhaps recalling that sinking feeling we've all felt after failing an exam, sees a thick red line on the mapLevel of Service Flooming in the future and knows this is very serious indeed. Something happens.

Because pedestrian and bicycle infrastructure lacks this precision of data, or any data at all in most cases, there is little scientific support for funding it. Technocrats see such projects as window-dressing on the business of real mobility, nice features that the Federal Highway Administration lumps together with museums and lighthouse renovations as "transportation enhancements." Most people reading this blog see things differently. But how do we prove it? And how do we efficiently allocate bicycle and pedestrian infrastructure investments where they will be most effective? Useful knowledge simply requires more data.

To be sure, people counting does happen. The National Bicycle and Pedestrian Documentation Project just finished an annual two days of counting earlier this month. Cities and towns across the country participated in the effort to acquire nationally standardized data. Annual "cordon counts" of bicycles have been conducted in downtown D.C., northern Arlington, and a beltway crossing since 1986, allowing some trends to be observed.

Yet a large majority of these counts have to be conducted by hand, with a pen and clipboard, by interns and volunteers standing on street corners. This can be a fun event once in a while, but there is no way to get enough data with this method to account for variances over time: daily and weekly commuting patterns, seasonal variations, responses to weather, special events or other external variables.

Humans are good at doing many things, but counting discrete objects over long periods of time is probably more easily done with computers. One study has shown that workers hired to track pedestrians routinely undercount them. We tend to get tired, eat snacks, and blink too much through hours of tedium. So I asked a friend of mine who studies visual recognition software at U.C. Berkeley about using cameras to count pedestrians on a street. He said the technology has certainly arrived, and the margin of error would be small enough for the purposes of data collection. Indeed, cameras are already commercially available for this exact purpose. For an intensely comprehensive academic bibliography on counting people, see here. Some automated counting has begun in U.S. cities, but it's only in the very beginning stages.

We have a need for better bicycle and pedestrian information. We have the technological means to acquire it fairly easily. We know how to model it and use the models from decades of counting cars. All that remains is the will to make this connection happen.

Daniel Nairn is a graduate student in Urban and Environmental Planning at the University of Virginia. He works, plays, and studies in Charlottesville. He also blogs at Discovering Urbanism


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A great place to run this would be Metro stations--that way you could accurately measure transfers, and also provide a rough upper bound on the number of people who can comfortably use a station.

by Dan Miller on Sep 24, 2009 11:14 am • linkreport

"Technocrats see such projects as window-dressing on the business of real mobility..."

Nicely worded. You hit the nail on the head.

by Matthias on Sep 24, 2009 11:46 am • linkreport

I look forward to the day I hear, "According to our projections, if we don't do something, within a few years our sidewalks and bike paths will be disastrously congested"!

by Gavin Baker on Sep 24, 2009 2:03 pm • linkreport

I realize this does not fully address your point but transportation engineering firms do count pedestrian and bike traffic when doing traffic surveys (I've conducted several surveys myself). Having this information made fully public may be another issue.

by Matt on Sep 24, 2009 4:29 pm • linkreport

I'm surprised you didn't mention the automated bicycle counters they have on the bike tracks in Copehangen (and other cities) the "cykelbarometer" (Complete with an air pump for your convienence. Yes, it's free). I'm sure the vendor would be more than happy to sell us a few.

There is a 'sensor line' in the asphalt on the bike lane a few metres in front of the counter which registers the cyclists. There is a SIM-card in the counters so the information is automatically sent to the City of Copenhagen's Center for Traffic. The counter only registers cyclists on this side of the street, not the far side, so you can double the numbers up to see how many cyclists use both directions.

by Lee.Watkins on Sep 25, 2009 6:45 am • linkreport

Maryland's data is public:

by Bossi on Sep 25, 2009 10:15 am • linkreport

I've seen occasional traffic count boxes set up along bicycle trails here and there during my bike rides. Not very often, but then again, most streets/highways only have traffic counted once a year or once every other year (and in some regions, up to 4-5 years between counts).

Counting bicycles, at least along separated paths, shouldn't be too hard. The difficulty is counting pedestrians. Aside from doing manual counts, I am not convinced that the technology exists to accurately count pedestrians.

by Froggie on Sep 26, 2009 10:41 am • linkreport

We've been doing experiments monitoring bluetooth discoverable phones as a very low-cost way of measuring a subset of pedestrian traffic. Unlike CCTV monitoring, it is easy to set up, and does something unique: measures return traffic. Add measurement nodes round a city and you can even track pedestrian movements.

Ongoing Paper:

by SteveL on Sep 28, 2009 8:20 am • linkreport

At the Arlington Bicycle Committee meeting in November, I was informed that the county has set up two ped/bike counters along two of the more heavily used trails. The one on the Custis near the top of the Rosslyn hill differentiates between peds and bikes.
It has a sensor in the ground that catches the bikes and an infrared sensor that catches everyone. Simple subtraction tells you how many of each.
They are already collecting a lot of very interesting and useful data.

by Steve O on Dec 1, 2009 9:52 am • linkreport

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