Automated trail counters have given Arlington an accurate count of the numbers of pedestrians and cyclists on various trails by time of day.

Below is the aggregated data from a counter located at the Custis Trail’s 3.5 mile marker, at the top of the hill, just west of Rosslyn:

There are three interesting things this chart shows.

The winter effect: Winter does cause a sizable drop off in cycling. It’s around 70%, as I eyeball it. It’s impossible to say if these are evenly dispersed among commuters and recreational cyclists or if the people left in the winter are dedicated commuters, but regardless, there is less biking in the winter.

The period of reduced cycling seems to be the 4 months from about mid-November to mid-March. That happens to correspond pretty closely with Daylight Saving Time, so it may be that people just don’t want to bike home in the dark.

The summer effect: There isn’t one. Next time you hear someone say that it gets too hot in the summer to bike in DC, show them this.

Snow plowing matters. The big drop off in trail use in February is during Snowmaggeddon and the resulting lack of snow clearing. Snow was done falling on 2/11/10 but it wasn’t until the first week in March that things got back to normal.

Some of the drop off would have occurred even if the trail had been cleared by the 12th because so many offices were closed, but clearly the lack of snow clearing on the trail made it almost unusable for about three weeks. During that time there were maybe 15,000-20,000 fewer trips on the trail than there might have been had it been cleared.

Some of those trips probably moved elsewhere, but not all of them. It’s worth asking how much those trips were worth and how much it would have cost to make them possible.

As Mark Blacknell points out, there isn’t enough manpower now to clear them, but that’s because of who is assigned to do it. Arlington’s Department of Environmental Services has 150 employees to clear roads. But trail clearing is assigned to the Department of Parks, Recreation & Cultural Resources, which has a single crew who has to clear routes to schools, paths to Metro stations and trails, in that order. By the time they get to trails, Mother Nature has done the work for them.

It appears that in the winter, they can count on about 5,000 bike and pedestrian trips per week — if they keep the trails maintained. If Arlington wants to promote active transportation, it is worth dedicating at least some of the road clearing crew to that purpose for both the purpose of making it usable and to signal the importance the county places on them.

Cyclists and pedestrians make up more than 0% of commuters. They deserve more than 0% of the plowing resources.

Cross-posted at TheWashcycle.