Radar Speeds

One of the frequently asked questions is whether the speeds reported are "relative" or "absolute". The speeds reported by the Varia are RELATIVE speeds. There are several places on the website displaying statistics related to vehicle speeds. If not mentioned specifically, the speed being reported is a RELATIVE speed.

"Incremental" speeds and ranges

Several people have complained that speeds seem to be incremental rather than changing smoothly. I am certainly not a radar expert, but my understanding is that to make the radar small and portable enough to fit into a relatively tiny taillight, speeds (and distances) are not going to be very fine-grained. It will essentially pick the closest "bucket" to put the approaching vehicle into. That bucket may change from reading to reading each time the radar is activated, but not for any given vehicle. Note that this is just my best guess about why the speeds seem to be somewhat "regular" bouncing between two identical speeds (adjacent buckets). There is no official documentation about this. Also, there is a reason why Garmin doesn't just natively display this speed value. They know that it is not going to be as accurate as the typical user may expect it to be. For my purposes, I just want to know which roads have cars passing you at higher rates of speeds than other roads and possibly why. I have ridden literally (not exaggerating) tens of thousands of miles with the radar and I do think the speed data that it reports is fairly consistent from measurement to measurement, but I do not think it is accurate (it seems too high).

NOTE: it is also entirely possible that the speed data varies dramatically from device to device. Other people have sent me their rides, and I'm always amazed at how the passing speeds seem lower than the speeds at which people pass me. That being said, I do have two different Varias (and a third which was destroyed in vehicle collision that initiated this project) that seem to report similar speeds, but I haven't conducted a controlled test to see if there is a major difference. It's on my very, very long to-do list but also low priority so I may never get around to doing it.

Experimentation

Here are some ideas for more more scientific experimentation to figure out a definitive answer about the speeds that the Varia radar is reporting. The basic design is as follows:

  1. Stand beside a professional radar system and compare the speed reported by the Varia to that reported by the professional radar system.
  2. Repeat #1, but this time while riding in same direction as approaching vehicle and again compare the speed reported by the Varia to the speed reported by the professional radar system.
I will update this page with the results of these experiments. Please email me your results if you conduct a similar test. Thank you!!!


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