Years ago, when I first heard of road cyclists using radar I probably scoffed as derogatory thoughts rolled through my head. “What a bunch of nerds.”
Now, with a few more years, grey hairs, and a kid, I put in a request to try Garmin’s Varia RCT715 (RCT is Radar, Camera, Taillight) and I’ve been using it for a few months. What follows is the reasoning behind my interest and my experiences with the unit. As usual with bicycle-related electronics, if you want a really deep dive into the hardware and software, DC Rainmaker has you covered.
To understand why we’re talking about adding another electronic device to your bike, I want to talk about the concept of situational awareness, or SA, and task loading.
SA is the understanding of an environment, its elements, and how it changes with respect to time or other factors. It is also defined as the perception of the elements in the environment considering time and space, the understanding of their meaning, and the prediction of their status in the near future. It is also defined as adaptive, externally-directed consciousness focused on acquiring knowledge about a dynamic task environment and directed action within that environment. – Wikipedia
While much of the research around SA was initially focused on aviation, cycling – in all of it’s forms – is also a dynamic task environment. As you move through the world, everything is in a constant state of change and SA involves monitoring everything from the trail/road ahead and behind, other trail/road users, and your bike’s noises. You then need to integrate all this information and ultimately act on it (or OODA if you prefer; observe, orient, decide, act).
While generally replaced with a glass-display version in modern aircraft , the Horizontal Situation Indicator (HSI) was designed to reduce pilot workload, bringing multiple, critical pieces of information into a single place for observation with one glance.
Our brains are also limited; there’s only so much information we’re able to observe, understand, and utilize in any given time period. Quantifying ‘task loading’ involves the accumulation of mental, physical, and temporal demands on us both mentally and physically. In commercial and military aviation, much effort is put into reducing task loading, because task saturation – a state where the volume or quantity of tasks exceeds an individuals capacity to process them – is a common cause of mistakes. In aviation this can be fatal. Put simply, making information more readily available to observe and easier to process reduces the chances of task saturation, increasing SA and the chances of survival.
Transport Canada lays out task loading on a pilot for a standard flight, reducing mental and physical effort of tasks gives more time for decision making, action, and ultimately increases the safety margin thus reducing the risk of accident.
For most mountain biking I do, all relevant information I need is available to me in straightforward fashion. I need to look ahead, listen to my bike, feel the terrain, suspension, tires, and use that information to put me on the best path at the appropriate speed, in the right body position, prepared for whatever’s next. Task saturation doesn’t really come into the picture, as my physical workload limits dictate speed more than mental workload (mind you, one of the biggest factors in how well I’m riding is how far I’m looking ahead… looking farther down the trail gives more time to go through the OODA process, enabling faster riding.)
Drop-bar riding can introduce a significant other variable into the workload equation; navigation. While less commonly an issue mountain biking*, navigation is a much bigger factor for my drop-bar riding: I’m often riding in places for the first time, urban environments can have lots of turns. The kooky gravel connectors I’m out to try are often hidden, and speeds are much higher, which allows less time for decision making as you approach a junction or corner. You can always stop to look at a map (some will remember we used to do this with actual paper maps, even mountain biking!), but now I usually ride with a Hammerhead Karoo.
*unless you happen to be on the spiderweb mazes of Southern Vancouver Island, often a navigational nightmare…
While my display preferences have changed a bit, and I’ve upgraded from the Karoo 2 to the current Karoo, being able to see the route ahead and other useful parameters at a glance has meaningfully changed riding in many scenarios, be it racing BCBR Gravel, exploring the SF Bay Area, or just going out for an hour inter-urban loop from home to find new connections.
Having a headunit out front enables me to get a picture of the upcoming navigational tasks with a quick glance down, no stopping to pull out a phone or map, or even slowing down required. If I see a junction ahead I can glance down, see I’ve planned to turn right, know it’s followed by a quick left, decide how much to brake, and act. Or I can be reminded with a beep that I’ve planned a hard left up ahead and to start looking for it. This is an example of how having information clearly available and easy to see increases SA, leads to easier decision making, and faster action, which means you can keep moving at high speed, avoid getting a heavy bikepacking rig moving again, or having to turn around.
Remember task loading, and how an accumulation of tasks can reach a breaking point and lead to mistakes? This photo represents a significant accumulation of mental and physical tasks when the train is in motion.
Towing a trailer around with a kid, their bike, maybe a whole camp setup, and your partner, introduces a whole new level of tasks to riding. When you’re pedaling a rig around that’s 110 pounds (before you add a kid), with a high COG, complicated by conversation, navigation in unfamiliar places, physical exertion, and a host of other factors, the hazards are heightened, and the consequences are increased. My SA is reduced by questions like, “How many days is it?” from the trailer, and the heavy task loading is noticeable. I can’t remember exactly when, but a rear-facing radar started to interest me.
Garmin Varia RCT715
Opening up the box, the RCT715 is heftier and bulkier than I expected; listed weight is 147 grams, and it’s 106.5 x 42 x 31.9 mm. Comparing to the RTL515, with identical radar/lighting and no camera, half of this bulk is the camera and associated accoutrement, with a 140° fov lens recording in 720p or 1080p. Syncing the ANT+ radar and light with my Karoo was drama-free; I’m able to adjust lights, see radar hits (more on that later), and get notifications on the Karoo. The camera runs a separate, Garmin-specific protocol, but while I don’t have access to all camera features on my headunit, it was a straightforward affair to set recording parameters and settings in the Varia phone app.
Physically mounting the RCT715 was a slightly more complex story and required a bit more ingenuity and DIY. This isn’t likely to be the case if you buy one and plan on putting it on your seat post, but as I was mounting mine on a ToutTerrain trailer it took a bit of fiddling. After some hacksawing, bolting, and partially disassembling the stock seatpost mount, we were in business and out the door riding.
Pairing was a standard ANT+ affair for the Varia and UT800 light; both are easily controllable within Hammerhead Karoo, with hardware buttons on each unit, or with mapped buttons on my brifters.
Your Varia will probably not require a custom mounting solution involving angled aluminum, thread taps, and longer shock bolts.
Be aware that the RCT715 doesn’t use Garmin’s standard quarter-turn mount, the beefy unit requires a sturdier connection. It’s been trouble free even in rough terrain. The other, lighter, camera-free Varias use a quarter turn mount.
Riding with the Varia
Lights
Quickly covering the basic function here, the Varia’s lights are bright, easy to control, have a bunch of modes that are all controllable from your ANT+ compatible head unit, phone, or hardware buttons, and have more impact on battery life than any of the unit’s other functions. Lights are rated at 65 lumens, which seems plenty bright in my experience. You can set the lights to turn on when you start your ride, sync with a front light (I’m using a Garmin Varia UT800, an 800 lumen, ANT+ compatible ‘smart’ light), and change settings on the fly.
Radar
Bike radar technology isn’t new, it’s been around for somewhere around 15 years, but this was my first experience with it. There were two distinct phases of riding with a radar. The first phase was a few weeks: getting used to the noises, figuring out how the visual display lined up to the real world, learning the devices capabilities. My first impression was that the radar was too sensitive, picking up cars that were too far back to be important, and my brain needed to understand how distances on the Karoo translated into the real world. If a car is halfway up the side of the Karoo, where is it behind me?
Eventually, I hit a second, ongoing phase of being able to fully take advantage of having an extra set of eyes on the back. Getting an audio-visual warning a car is coming from way back, once I adapted, is great. The Varia observing gives me extra time to orient, decide, and act, choosing between continuing on, pulling over, trying to avoid an upcoming pinch-point, or any other option. Extra time allows me to make better decisions, and with a big, heavy rig and precious cargo, I’ll take all the extra help I can get. While your eyes and ears remain indispensable, having a constant, vigilant, un-fatigueable electronic companion out back measurably reduces my physical (looking back, constant listening) and mental (thinking about when to look around, short decision times) workload.
There’s a unique audio cue for when the unit senses a car to alert you. The vehicle can then be tracked on approach on the screen. It took a little while for me to get used to how this translated; Garmin lists 150m as the detection range, but this is variable based on environmental factors. I’ve seen shorter, and also longer.
Multiple cars can be tracked simultaneously. If a vehicle is approaching rapidly, there’s a more urgent audio cue, as well as a red line instead of yellow to alert you of the increased closing speed and danger.
Green indicates a threat has passed – if there’s multiple cars you won’t see green until no additional vehicles are detected.
As an example scenario, I’m pedaling to school towing the trailer and there’s a chirp chirp from my Karoo. I’ll glance down to see how far off it is, and eventually look back to verify and see what kind of vehicle is coming. Then I’ll look ahead at the road ahead to evaluate hazards like road width, driveways, upcoming intersections, parked cars, etc. Deciding there’s enough room to continue on in the curb lane, despite a parked car ahead, because the vehicle behind should have passed me by the time I get there. I can also keep an eye on distance to the approaching vehicle behind on the head unit.
The Varia now indicates there’s three cars in a line, which I think might not all get past me before I reach the parked car. Looking back to ensure I’ve got enough room, I fully take the lane, pulling over back to the curb lane to let the line of car traffic past after I’m beyond the stationary vehicle. While the Varia doesn’t negate the need to glance back as cars get close, to ensure they’re giving enough space to pass, being able to immediately identify and monitor threats without looking backwards all the time is incredibly helpful.
Overall, in urban settings, the audio cue can be excessive as there’s sometimes just too much traffic, I’m already on high alert, and additional beeping doesn’t help anything. I’ve got a hardware button on my SRAM Force XPLR brifters mapped to turn the audio on and off. This means I can press the button without removing my hands, which also reduces my workload.
On less busy roads, on long rides, and in situations where I’m already taxed physically or mentally, I’m thankful to have the Varia looking out back for me, and the audio alert is much harder to miss than a car coming up behind you quickly, especially if there’s wind, or other noises. There are occasional false positives for pedestrians or other cyclists (better than missing vehicles), and occasionally if you’ve had a car following you at similar speed for a period of time it’ll disappear off the screen, but on the whole the Varia’s radar is very accurate.
On a trip to Saltspring Island, I discovered that balloons – if tied to the Varia – will confuse the detector. When there’s a malfunction like this, there’s an audio-visual cue on the Karoo to let you know not to trust it.
Camera
The camera isn’t something I spent a lot of time with. There’s a few features, and sure, if you’re on a group ride, you can record pictures or video of your paceline or what have you, but for me it is an insurance policy. If an incident happens, hopefully there’s something useful recorded. Image quality is good enough to read license plates, and it’s regularly tempting to post footage of parents blowing past us to the class WhatsApp chat. There are more features available on Garmin head units, with the ability to set recording sections, take photos, and other settings, but nothing I find myself missing out on; all I want is useable footage in case of an incident and nothing more.
The Varia automatically ‘locks’ certain video clips if it detects significant accelerations. I periodically have to go through and delete all of these as they don’t get overwritten and wind up using most of the memory card after a few months.
Three example clips in the 1080p mode. In the night clip it’s difficult to read license plates, but in the daytime they’re generally legible. There’s some YouTube compression here which makes it more difficult, the full files are better, although they could be better.
Conclusions
Do you need to go out and buy radar? Of course not.
Does having one reduce my risk of f*cking something up due to task overload, and reduced SA? I believe so. My experience here has been positive, and while the chirp chirp from my Karoo can be a little annoying on busy streets, I will happily to tolerate it because cars aren’t just a little annoying, they’re dangerous. It’s another thing you need to keep charged, but since I was already running a rear light, there’s it isn’t any more work. The Varia lasts for about a week of my usage, and unlike my previous rear light I’ll get a notification when it’s time to recharge the Varia.
Is the Varia RCT715 worth 579 CAD / 400 USD of your hard-earned dollars? I can’t make that call for you, but I can quote DC Rainmaker, “to re-iterate what virtually every single forum/post/review/etc will tell you from the past near-decade: Virtually everyone that has the Varia radar says it’s the greatest thing they’ve bought.” I’d strongly consider saving 300 CAD and getting an RTL515 as the RCT715 is significantly larger and heavier, but should the worst ever occur, you might be glad you have footage.
The RCT715 has become a fully integrated part of my drop-bar riding, especially when family is involved. It helps reduce my workload with a constant set of watchful rearward eyes, keeps me and my compatriots/passengers safer, and in a worst-case-scenario, I’ve got footage. As usual, fire away below with questions or comments.
Your mileage may vary, but in situations like this I’m glad to have the Varia out back; I can enjoy the ride more, chat with my passenger, worry less about constantly looking over my shoulder to see if an EV is sneaking up on us, and worry more about the upcoming 18% grade.
Elder millennial, size medium.
Reformed downhiller, now rides all the bikes.