Counting Bikes to Plan for Bikes

View the BikeArlington Counter Dashboard here!Photo: group of bikes at intersection

An old adage says “you can’t manage what you don’t measure”. In response, Arlington County transportation planners have established a robust program of continuous, automated bicycle and pedestrian counters to generate data on bicycle and pedestrian transportation. The count data strengthen the case for continued investment in and encouragement of active transportation, and help direct efforts to have the greatest impact.

Traditionally, bicycle trip data came from a combination of manual counts and surveys. But both methods are labor intensive, prone to inaccuracy and subjectivity, and provide limited insight into the everyday and long-term “pulse” of active transportation. Imagine working for weeks to organize a team of volunteers for a count event, inducing them (perhaps with cookie bribes?) to commit to a day of street corner observation with a clipboard, only to have the event washed out by a thunder storm. Or, perhaps the weather cooperates, but, on compiling the results, it is found that some volunteers did not follow directions carefully, so there results are flawed, unrepresentative, or unusable. There are many arguments to be made in favor of electronic surrogates that work 24-7-365, rain or shine.

Arlington’s first two automated bike and pedestrian counters were installed in the Fall and Spring of 2009-10 on the Custis and Four Mile Run Trails. They use a combination of in-ground inductive loops, passive infrared detectors, and pressure-sensitive piezo technology to generate data on trail volumes and travel direction. (Yes, for the curious, the occasional deer might get also be counted as a pedestrian).

As of this writing, in January 2015, the County has 18 permanently installed bicycle and pedestrian counters on shared-use trails, 10 permanent bicycle-only counters in on-street bike lanes, 6 mobile counters typically used for short term sidewalk counts, and the first real-time bicycle counter on the east coast, which we call the #bikeometer. This device, near the intersection of Lee Highway and N Lynn Street in Rosslyn, shows cumulative daily, monthly, and year-to-date totals at one of the busiest bicycle locations in the region. For nine months in 2014, from its launch on April 1 until December 31, the Bikeometer registered nearly 320,000 bicycle trips. We think the database we are building is not only valuable in the near term for planning and forecasting, but will also pay dividends for years to come as a record of active transportation.

Some early insights derived from the data include:

  • People are riding a lot of bikes on County trails! Most of our major trails see around 500,000 trips per year.
  • People ride on these trails to commute to and from work, for recreation and fitness, and for social and utility trips. Some of the trails display a balance of uses – other locations are predominantly used by commuters or recreational riders.
  • Many cyclists are not deterred by winter cold temperatures alone. But rain, snow and ice do have a major deterrent effect on ridership.
  • We enjoy a solid 6-7 month high season of strongest bicycle numbers.

Figure 1: Bike and Pedestrian Trips on the Custis Trail West (Uphill) of Rosslyn

Click image for larger version.
Alternate content: Figure 1 graph data in HTML table

Graph: Bike Trips on Custis Trail, Arlington County

Figure 1 shows activity over 62 months on the Custis Trail, an off-street, paved, multi-use trail running east-west across Arlington along I-66.

Peak months approach 50,000 trips, and peak days can come close to 2,000 bicycle trips. Imagine if all those trips had been additional vehicle trips on I-66 and other already congested roads. Cycling is making a difference! We have seen an average annual increase of nearly 5% in bicycle trip numbers over four complete calendar years.

Figure 2: A.M. and P.M. Commute Hours

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Alternate content: Figure 2 graph data in HTML table

Graph: Custis Trail Peak Hours

Figure 2 shows a.m. and p.m. spikes on the Custis Trail, typical of a commuter travel pattern.

Even a casual observer would notice that most riders carry backpacks or panniers during commuting hours. This regular, predictable, dependable activity sends an important message. The Custis Trail is a popular and valuable commuting facility, and not just a recreational trail. In fact, it’s more popular on weekdays than weekends. The counter data underscores the importance of the Custis in the inevitable competition for limited resources, and in support of Arlington’s dedication to providing transportation options.

Figure 3: Effect of Weather

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Alternate content: Figure 3 graph data in HTML table

Graph: Effect of Weather on Bike Trips

Figure 3 shows the effect of the weather on bike trips.

Cyclists on the Custis Trail are much more averse to rain than to merely cold temperatures. This observation helps strengthen the case for continued trail maintenance and snow clearing throughout the winter. If the trails are clear of snow, many people will choose to ride despite the cold. A relatively small investment in clearing the trails keeps people on their bikes, and means fewer cars on the road, and less crowding on buses and Metro trains.


From two original counters installed in 2009-10, Arlington County has grown a network that now includes 18 bike and pedestrian counters on off-road shared-use paths; 10 counters in on-street bike lanes; six mobile devices suitable for short term bike and/or pedestrian counts, and the first real time bike counter on the east coast, the Rosslyn #bikeometer. The wealth of data these devices generate helps legitimize cycling as a valid form of transportation, and guides the continuing efforts of transportation planners. So the next time you ride in Arlington, remember – we are “counting” on you!

Did You Know?

Each U.S. rush-hour auto commuter spends an average of 50 hours a year stuck in traffic.

League of American Cyclists

RackSpotter -- Crowdsourced Arlington bike parking map

Arlington’s Bicycle Counters

Bikes counted

View Counter Data
14th Street Bridge
1643
Ballston Connector
318
Bluemont Connector
236
CC Connector
756
Clarendon EB bike lane
217
Crystal SB bike lane
89
Custis Bon Air Park
1280
Custis Rosslyn
1348
Fairfax EB bike lane
132
Joyce St NB
42
Joyce St SB
30
Key Bridge East
1411
Key Bridge West
641
Military NB bike lane
68
Military SB bike lane
57
MVT Airport South
3224
Quincy NB bike lane
57
Quincy SB bike lane
78
Roosevelt Bridge
350
Rosslyn Bikeometer
1389
TR Island Bridge
1848
WOD Bon Air Park
1908
WOD Bon Air West
2247
WOD Columbia Pike
1574
WOD East Falls Church
1895
Wilson WB bike lane
278

All bike counters, YTD

View Counter Data
Year to Date
2510890
About Arlington’s Bicycle & Pedestrian Counter Program

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