Like this site? Help us to make it better.

Garmin Varia RTL510



Useful early warning system with a bright rear light, but quite pricey

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

What the scores mean

Good scores are more common than bad, because fortunately good products are more common than bad.

  • Exceptional
  • Excellent
  • Very Good
  • Good
  • Quite good
  • Average
  • Not so good
  • Poor
  • Bad
  • Appalling

The new Garmin Varia RTL510 is a product I never knew I needed. It's an early warning detection system that lets you know a car is approaching from behind, which is a godsend on the rural roads I regular ride; it also syncs perfectly with a Garmin Edge (no surprise there) and is a very bright rear light.

  • Pros: Early warning detection, syncs seamlessly with Edge computers, bright light, easy mounting, sleek looks
  • Cons: Expensive

A few years ago Garmin launched the Varia radar system, a rear-facing radar device that linked to a handlebar unit to warn of approaching cars, their proximity and speed of approach. I'll be honest and didn't really think much of it. I mean, what's wrong with looking over your shoulder?

> Garmin launches new Varia radar system + remote controlled lighting

But I'm open-minded and happy to try new things, so I was intrigued to try the newly updated Varia RTL510, which combines the radar technology with the light tech from Garmin's Varia rear lights. I've been increasingly running daytime rear lights so this seemed like the ideal product for me.


And I have to admit I've been really impressed. I won't go as far as saying it's one of those products that I ever wondered how I coped without, but it's not far off. Let's be clear, it doesn't replace your own senses when it comes to being alert to other road users, and it's arguably not going to make you safer. But what it does and what impresses me is that it detects an approaching car far sooner than I would.

The range of detection is 140 metres and every time I've looked over my shoulder after first being warned of an approaching car, I've been surprised by just how far away the car is.

So it does act as a really useful early warning system, and for riding the quiet country roads that I do on a daily basis, I like that.

Heads up

The Varia RTL510 can be synced to a dedicated radar display unit, or it can be paired with a Garmin Edge computer. I've been doing the latter, testing it with an Edge 820 and more recently the new Edge 130 (review to come). You can view all compatible devices here.

Pairing the Varia RTL510 to the Edge is a doddle: you simply connect it as a new sensor via ANT+. That's all you have to do. You know it's connected because you have a small radar symbol in the top corner. The Edge can also connect to the light and switch it on and off automatically when you turn the Edge computer on and off, which is pretty neat.

Fitting the Varia to the bike is also simple. The mounting bracket attaches using a rubber band – there are two different rubber adapters to suit round and aero seatpost – and the same quarter-turn interface as the computers fixes the Varia in place.


It's a vertical design and is fairly unobtrusive on the bike. It's not much bigger than other lights on the market and it's a fairly sleek design.


Then you go ride your bike. The first warning you get of an approaching car is a beep. After that, a thin column appears on the side of the screen (you can customise which side of the screen it appears on), with a dot at the bottom representing the car and position relative to yours, represented by that small radar logo in the top corner. The colour of the column indicates the speed of the car: amber is standard and red light means to take care, a car is approaching at high speed.

I was asked a question on Instagram along the lines of 'great idea, but surely it trades one risk for another?' It's a really good question. What I've found is that the warning beep is the best part of the system, and rather than constantly looking down at the screen, I just make occasional and quick glances to see where the car is.

Be warned

Why the Varia appeals, and why I've taken to using it for every ride, is because I'm happy to admit there have been occasions when I've been surprised by a car passing me, simply because I've been deep in thought or just let my mind wander, or because it's really windy and your hearing is impaired. That surprise factor hasn't happened once with the Varia. 

So that warning beep serves a very useful purpose. As a result, I've found I'm not checking over my shoulder 'just in case there's a car approaching' as much as I used to. You shouldn't depend on the Varia completely, but you pretty much can. What you can't see is that the Varia light blinks when a car is overtaking you to serve as an additional warning to the motorist.

After that beep occurs, it's easy to quickly glance at the computer screen to see where the car is in relation to your position, but that element is secondary in my opinion to the early warning beep. It is useful when it shows two cars on the screen, the maximum it can display.

Rear light

The other bonus is the extremely bright 60-lumen rear light that is incorporated into the unit. It has a claimed visibility range of one mile and has a run-time of 15 hours in flashing mode or 6 hours in solid and night flash mode. The light also has a 220-degree range to provide some side-on visibility and means car drivers should see the light before the radar sees them.


The Varia is easily charged via a USB port and the Edge serves up a low battery warning which is useful.

City limits

It works really well on country roads where traffic is light. Riding through towns reveals it can be triggered by parked cars which does reduce its usefulness to a degree, and I'm not sure given the hustle and bustle of busier towns that it would be as useful – when you've got a constant stream of cars passing, you don't need to know there's a car 140 metres away.

But if your commute or ride starts in the city and takes you out into quiet country roads, as most weekend cycle rides likely do, then it's a useful addition. It could also stop you being caught unawares by near-silent electric cars.

What about when you cycle with other cyclists? I've used it both in a chain gang and club run and both times it wasn't fooled by the cyclists following in my wake, yet was still able to detect a car approaching our small group. So it works well in those circumstances as well.

Warning or camera?

There's no denying it's a pricey investment. You are getting a rear light as well, although even a normally expensive rear light such as the Exposure Blaze Mk1 Daybright is still cheaper at £90. But there is nothing else like the Varia on the market – the only vaguely similar product could be the Cycliq Fly6, a £175 rear light with an integrated camera.

Choosing between the two comes down to whether you prefer to film close passes or have an early warning system, and much of that probably comes down to how busy the roads are that you regularly ride.

Obviously, the Varia isn't going to prevent a close pass or a car hitting you. But if you're riding along a quiet country road and a car comes out of nowhere at speed (as happens frequently in the Cotswolds) then it does give you that warning. What you do about it is up to you, but knowing there's a car approaching often before you actually hear it is a positive thing.

I know I will cope just fine when Garmin asks for the Varia back, but having ridden with it for several weeks I've really got used to the early warning system. Would I part with £170 for it? I'm not sure I could... But if price is no obstacle then it's a no-brainer and I'd tell you to go out and buy one.


Useful early warning system with a bright rear light, but quite pricey

If you're thinking of buying this product using a cashback deal why not use the Top Cashback page and get some top cashback while helping to support your favourite independent cycling website test report

Make and model: Garmin Varia RTL510

Size tested: n/a

Tell us what the light is for

Garmin says, "Ride smarter and more aware with Varia™ RTL510 rear-view radar. Mounted neatly on the seat post, it provides visible and audible alerts for vehicles approaching from behind up to 140 metres (153 yards) away. Plus, the bright tail light is visible in daylight from up to 1.6 km (1 mile) away, so you can ride with confidence and peace of mind.

This sensor has your back

While out on a ride, you have to keep track of everything. What's your route, how far you're going, how fast and how hard you're going to push it. But with Varia radar along for the ride, it's like having eyes in the back of your helmet. It's essentially an early warning system so you see cars approaching from behind and they see you.

This sensor has your back

Safety in numbers

Varia™ RTL510 rear-view radar is just one part of cycling awareness. When paired with compatible Garmin devices the system helps to create safer riding conditions by alerting riders to vehicles approaching from behind. Green light? All good. Amber light? A vehicle is approaching. Red light? Take care - a vehicle is approaching at high speed. Ride safe."

Tell us some more about the technical aspects of the light?

From Garmin:

Provides visual and audible alerts to warn of vehicles approaching from behind up to 140 metres (153 yards) away

Tail light offers daylight visibility up to a 1.6 km (1 mile) away and is visible within a 220-degree range, so drivers can see you well before the radar sees the vehicle

Sleek vertical design easily mounts to most road-use bicycles, including racing, touring and commuter styles

Requires a dedicated radar display unit (sold separately) or wirelessly integrates with compatible Garmin devices1

Battery life: up to 15 hours in flashing mode or 6 hours in solid or night flash mode

Rate the light for quality of construction:
Rate the light for design and ease of use. How simple was the light to use?

It's a doddle to use, there's just one button on the unit itself.

Rate the light for the design and usability of the clamping system/s

The clamping system provides a secure connection to the seatpost and it doesn't shake or rattle about, even on off-road trails.

Rate the light for waterproofing. How did it stand up to the elements?

It hasn't rained in ages, but I subjected it to the hosepipe test and it was just fine.

Rate the light for battery life. How long did it last? How long did it take to recharge?

I got pretty close to the claimed 15 hours – that's likely more than enough for a week's worth of riding for most people.

Rate the light for performance:

Really impressed with the performance as an early warning system.

Rate the light for durability:

Early days but so far, so good.

Rate the light for weight:

It doesn't add much weight to the bike at all.

Rate the light for value:

This is a tricky one. It's expensive yes, but there are no rivals on the market and it occupies a real niche. I think if you like the safety appeal of the Varia you might just be able to justify the price.

Tell us how the light performed overall when used for its designed purpose

The light is bright with a good 220-degree range.

Tell us what you particularly liked about the light

Bright and it blinks when a car passes you.

Tell us what you particularly disliked about the light

More side-on visibility perhaps.

Did you enjoy using the light? Yes

Would you consider buying the light? Yes

Would you recommend the light to a friend? Yes

Use this box to explain your overall score

It's an expensive but really useful product especially if you mainly cycle on rural roads.

Overall rating: 8/10

About the tester

Age: 31  Height: 180cm  Weight: 67kg

I usually ride:   My best bike is:

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo-cross, commuting, touring, mountain biking

David worked on the tech team from 2012-2020. Previously he was editor of and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds, and you can now find him over on his own YouTube channel David Arthur - Just Ride Bikes

Latest Comments