Originally Posted by
Iride01
My son's been suggesting that a Garmin Varia might be a good X-mas gift for him. I've known about them ever since they came out and have read
DC Rainmakers article on them.
I've had one almost since they came out. I've used it both as a standalone system and with an Edge 1000.
Do you generally get at least 5 seconds warning on traffic when you are on roads with 50mph plus traffic?
Yes, *almost* always. It's more useful on the highway than it is in an urban setting. That said, it doesn't look at traffic behind you, it looks at the difference in speed to objects behind you. So if you are, for example, riding at the same speed as traffic, then the threat behind you disappears. This, of course, can be disastrous if you make a hard turn in from of that same speed vehicle and get hit.
How useful in slower city traffic is it?
IMO, "much less" to "not much" and for three reasons:
1. Threat overload: There are simply too many vehicles and if you spend your time looking at the display and trying to figure it out, you'll lose your situational awareness. The display also gets a lot busier.
2. The disappearing act that threats do when there is no speed differential. This can be dangerous. This is much, much more likely to happen in an urban setting where a cyclist is moving at far less of a speed differential to cars than on a highway.
3. You need to be looking all around all the time anyhow in the city. Having one more thing to scan is not particularly helpful.
My son thinks it'll also tell him about other cyclist coming up behind him? I can't find anything conclusive on this. I know Garmin only talks about cars and such. I'm thinking maybe it will if there is a large overtaking speed.
It mostly will, BUT it's a deadly mistake if you don't look behind you. I find it far more useful on the highway in the country than in *any* level of an urban setting. My riding is primarily rural but passes through some small towns. In the town, it's not effective, but on the highway, it is more so. There is the problem of speed differential mentioned before and there is also the problem of how threats can be masked behind other threats. For example, if a truck is coming down the road followed relatively closely by a car, your display will show the truck threat and not the car threat. So you're missing one high speed vehicle behind you if you just believe the display.
Another problem is masking by curves. If you are riding around a curve, the Varia may not see another car coming behind you until it lines up behind you. In that case you will have much less than the 5 second warning you have become accustomed to. Basically, it can look behind you for about 450 feet (give or take) - do the math with respect to speed and if not in a relatively straight line back to you.
I don't think it's particularly useful as a standalone system and that it has a fatal flaw. When you use it with a Garmin bike computer, it will give you a beep (audio alert - wimpy though Garmin beepers are) when it picks up a threat when there was not a previous threat on the display. The standalone head unit that comes with a complete Varia system has no audio capability. I can't believe they omitted a cheap little beeper! You then just happen to have to look at the display to see if there is something behind you. I find that I get surprised just with traffic behind with the standalone system about as much as I would otherwise without a mirror.
I find a mirror mounted to my sunglasses to be much more useful (and much safer) but you have to scan it just like you would in a car - taking a quick look before any maneuvers and roughly once every few seconds otherwise. The Varia is no substitute for not looking behind you and can easily lead to false sense of safety because of the measurement of speed differential instead of absolute threat.
So it's useful, but you really, really need to understand it's limitations. If you don't understand those, then I think it's actually more dangerous. I got surprised by a car pacing me in a small town. I moved into the lane way, way too close in front of the car thinking there was nothing there because it didn't show on my display. I got a terrible scare and thank heavens that driver behind me was on the ball - she hit the brakes hard and didn't hit the horn. I got home, changed shorts (kidding), and called Garmin support only to find out it just looks at differential speed. Imagine my surprise.
J.