Garmin Varia RTL515

The Garmin Varia RTL515 combines a radar and a rear light. The light is bright, while the radar gives you an effective early warning for 'objects' overtaking. Both work well, and made me feel safer on the road, but the price is premium.

My initial thoughts on this radar system were the same as Dave Arthur's before he reviewed the previous version a few years ago: why do I need this? I can look over my shoulder, and I can hear cars approaching.

Yes, you can do both those things. Or you can add a mirror, which is cheaper. But the Garmin will tell you that an object is going to overtake you before you can see or hear it, and without having to take your eyes off the road in front of you.

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When the Garmin detects something, it'll give you a distinct multi-tone sound that is loud enough to hear over any wind noise. On a clear open road, quite often when I hear that sound, I'd look over my shoulders and only just be able to make out whatever is coming up behind me. The quoted detection distance is 140 metres; in real life that translated into impressively far away. On winding roads that distance is obviously shorter, but if the radar can't see it, chances are your eyes won't either.

If, like me, you think that is useful and will make you feel safer on the road, and you're prepared to spend £169.99, you can stop reading now and just go and buy one.

Overtaking objects

You might have noticed that I've not said 'cars' overtaking. The radar doesn't know what is coming up behind you. It just knows that there is something that is going faster than you, closing the distance, and will have to get around you if it is continuing at the same speed.

Could be a car, could be an artic, could be a tractor. Could be a fellow cyclist. I don't think it matters – I want to know something's going to overtake me first; what is of secondary importance.

The radar also attempts to tell you how fast the overtake is going to be, by changing the colour in the sidebar of whatever you've paired the radar with from amber to red – more about that in a minute. I found this slightly less useful; the overtakes don't consistently feel faster with the red colour, or less fast with the amber colour.

Also, the radar can't tell you how dangerous the overtake is going to be, as that depends on the road conditions, oncoming traffic and how close the pass will be – all things the radar can't predict. In other words, it just tells you something's coming up behind; it's not going to stop a crash – you still need to keep your wits about you.

Alert reliability

I didn't experience any false negatives with the radar; I can't recall a situation where something overtook me without the radar telling me about it.

Riding in a group, I did experience a small number of what you might call false positives, where the radar beeps but there is no danger, as other cyclists triggered the warning. It didn't happen often enough to be annoying, though.

What's also useful is that in this situation you can mute the sound from your chosen head unit. This also comes in handy when you're riding in traffic busy enough where 'object approaching' is basically always true.

Pairing options

The RTL515 connects over Bluetooth and Ant+. You can pair it with your Garmin head unit or watch of choice, but also a Wahoo Elemnt, Hammerhead Karoo or Stages head unit. There's a phone app, and thanks to the Bluetooth connectivity, third party apps can connect too – RideWithGPS, for example. You can also buy a separate dedicated head unit for £44.99 if you prefer riding without a phone or GPS unit, but you do want radar.

Hammerhead's Karoo 2 is my head unit of choice, and this is what I used for testing the radar. Setting it up is easy – just bung the Garmin radar in pairing mode by pressing the (only) button on the top for long enough for the little sidelight to go purple. The head unit will detect two sensors: one for the radar and one for the light. And that's you set up.

On the Karoo, there are no setup options for the radar; reading other reviews, it looks like you do get some on Garmin head units, such as the choice of showing the sidebar on the left or right of the screen, and whether you get a single tone or multi-tone alert. For the light, you can choose the default light setting.

When you start a ride, the Karoo will now do the sound and show a sidebar when the radar detects something. Like I said above, the sidebar will be amber for what the radar deems a 'normal speed' approach, and red for a faster approach. When the object has overtaken, or is no longer detected, the sidebar turns green. There is a little car icon for each object detected in the sidebar too, useful to know if more than one object is coming up.

The light will switch to the default option you've chosen in settings, and switches off when you stop a ride. You can change the light setting on the head unit while riding, like you can mute the radar sound while riding.

The Karoo also shows alerts for connection dropouts, which happened a handful of times in the more than 1,000km I've used it. The connection restores itself pretty quickly without me having to do anything, so no biggie. You also get low battery warnings.

In all, the user experience of the whole system feels sorted; there isn't anything I'd want to see changed.

Rear light

Just like the radar, the rear light works really well. I've used it mostly on what is called 'fast flash' in the Karoo settings, which translates to 'day flash mode' in Garmin speak. For me, this flash pattern and brightness are just right and better than most other dedicated rear lights. Visible, but not annoying. Bright, but not blinding.

Obviously not visible to you as the rider, the flash pattern changes when a car (or other vehicle/object) approaches, to try to make you even more visible to the driver.

Whether the driver being aware of your presence will always mean a safe overtake with plenty of space is another thing. Wouldn't that be nice.

Battery life and charging

On day flash mode, the quoted battery life is 16 hours. In real life conditions, a recent nearly 300km audaxy/eating contest type ride confirmed that to be about right.

Charging is via the Micro USB port on the back of the light; it'd be nice to see USB-C here, but as the form factor is exactly the same as the previous version, I can sort of see why it isn't.

Mounting options

The radar uses Garmin's quarter-turn mounting interface, and comes with a rubber band-on mount to go on a seatpost. You get three inserts to go on the mount to suit your seatpost shape: V for aero, square and round.

There are plenty of other mounts available from Garmin and third parties for attaching it to your saddle, saddle bag, child seat and so on.

Value

Okay, £169.99 is a lot of money, and that is assuming you already have a head unit or phone to pair it with.

Yes, you can do without, and yes, a mirror does a similar thing for less. However, this radar alerts me to cars behind me before I can see or hear them; and because of the beep it does so without me having to keep an eye on anything but the road ahead of me. I didn't think I would before I tested this, but I can see myself getting my credit card out when this one goes back to Garmin.

> Buyer’s Guide: 10 of the best rear lights for cycling

As far as I know, there is nothing else on the market that does what the Garmin Varia does. You could buy just the radar from Garmin, the RVR315, and save yourself £40. I don't know why you'd do that, though, as the rear light on the RTL515 is really good, and it interacts with the radar, and so makes the radar (slightly) better.

It's also worth noting that Garmin has kept the price the same as the previous version. 

Conclusion

Before I reviewed the Varia, I didn't think I needed radar. Now, I'm convinced it makes my riding safer, because it alerts me to overtaking objects before I can see or hear them. The rear light is among the best in class in terms of flash pattern and brightness too.

Although at £169.99 it's expensive, it's not as costly as being hit from behind. It's up to you whether you want to spend your hard-earned on making that less likely.

Verdict

Reliable alert system for being overtaken, with a very good rear light