Jun 23, 2011

The Futility of Average Time

So, I sprung for a snazzy new Garmin GPS cycle computer about two weeks ago and have been playing with it on my recent rides.

It's actually not all that fancy as these things go. I don't have cadence (I know my cadences without being told, thanks) and I don't have a power meter. I just want basic speed, elevation, time, etc. and this Garmin 500 Edge covers those bases nicely.

I love that I get route data that I can upload to Garmin Connect (the Garmin "cloud" site for keeping and tracking ride information). Here's an example of what you get - this is data from the last 3-speed ride, so the speeds are not impressive, but the route is well-mapped and is there for future reference; I can link it or send the URL to anybody that cares to recreate this ride for themselves. Handy as hell, really.

What's frustrating to see from the charts and graphs is the impact that stop signs and red lights have on my average speed. It seems every time I look down at this unit, I am motoring along nicely and keeping up with the cars, but then when I get home and look at the data, my average speed is a little below par for a TCBC "C" level. WTF?

Here's an example of a speed read out from todays commute (there and back, merged together). I think the slow flat spot is when the GPS lost connection in the parking ramp, but it's hard to tell for sure. This ride was completed on my relatively low-geared single speed mountain bike rocking 2-inch Big Apple tires:

What's immediately obvious is that this an absolute saw-tooth pattern. Any hope of a sustained speed must be abandoned on an urban commute. The cruising speeds are between 14 and 16 mph, with some peaks to 18 - 19 mph on the down-hills. What torpedoes my average speed are the red lights and stop signs. Zero is an awfully powerful number when it comes to pulling down an average. One and Two are pretty powerful as well. Add a long light and you've got no hope of an impressive ride.

To be clear, I have never been "fast", but I pass most people and rarely get passed. Nevertheless, according to the data, I would be desperately hanging onto the last wheel of a C ride. Ridiculous.

I am always skeptical when people tell me their "average speed". If it's at all high, they either road on rural roads, or they are telling you what the computer told them most of the time when they looked down at it. It's just not possible to average a decent pace in the City.

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