I tried Trek's CarBack Bike Radar — it's like having eyes in the back of my head

 Trek CarBack Radar Rear Bike Light shown mounted on the seat post of a green bike with green foliage out of focus in the background.
Credit: Dan Bracaglia/Tom's Guide

I love to ride my bike on city streets. I'm also intimately aware of the risks that come with it, particularly regarding distracted drivers. I've had numerous near misses with folks too sucked into their smart devices to notice others around them. I've also had one harrowing full-blown crash, again, the result of a distracted driver with his nose in his phone.

So, it's no surprise I take bike safety seriously. This includes wearing one of the best bike helmets, particularly one with MIPS technology. At night I opt for the Lumos Ultra which has built-in LEDs for visibility, during the day I wear an Abus GameChanger 2.0 helmet in white to be seen.

The Trek CarBack Radar Rear Bike Light shown in someone's hand with the rubber connecting strap visible against a light orange background
The Trek CarBack Radar Rear Bike Light shown in someone's hand with the rubber connecting strap visible against a light orange background

I'm also sure to switch on a set of the best bike lights before taking off on a ride, regardless of the time of day. But, up until this week, I've never used a bike light that doubles as a car-detecting radar device.

The Trek CarBack Radar Rear Bike Light is a $199.99 accessory that mounts to your seat post and pairs with your smartphone, smartwatch or bike GPS computer. Similar to the Garmin Varia, which is also $199.99, these two devices represent a new category of smart safety accessories for cyclists.

I tested the Trek CarBack on one of my favorite urban rides around Seattle, Washington. Here are five reasons why it's already won me over.

1. You get audio and visual alerts

The visual alert screen for the Trek CarBack bike radar showing icons of cars at varying distances for the cyclist.
The visual alert screen for the Trek CarBack bike radar showing icons of cars at varying distances for the cyclist.

I paired the Trek CarBack with my iPhone 12 Mini — more on the setup process below — which I keep mounted on my handlebars (using Peak Design's Out Front Bike Mount) while I ride. With my phone positioned for easy viewing, I was fully able to test out the device's visual warning system. I also wore Bluetooth earbuds to try the audio warnings.

When a car first approaches from behind, you'll hear an 8-bit-sounding set of tones that sounds a little like the one-up noise from the Super Mario Bros for NES. These tones play each time a new car is picked up by the radar.

When a car first approaches from behind, you'll hear an 8-bit-sounding set of tones that sounds a little like the one-up noise from the Super Mario Bros for NES.

Cars can be detected as far away as 787 feet. In addition to the Mario sound, detected cars appear on your smartphone or bike's GPS screen and move in real-time. The app displays not only the vehicle's distance from you but whether or not it has clearance to pass.

If a vehicle is approaching directly behind you from less than 250 feet away, the symbol in the app turns red.

Once the coast is clear and all cars have passed, you'll be met with a friendly doorbell-sounding set of tones.

2. Setup and installation is simple

The Trek CarBack Radar Rear Bike Light being affixed to a seat post using the rubber strap
The Trek CarBack Radar Rear Bike Light being affixed to a seat post using the rubber strap

I was seriously impressed by how easy the Trek CarBack is to set up and install. The companion app, TrekAcessories, is pretty barebones, but then again, everything works as it should, so that's not necessarily a criticism.

With the Trek CarBack switched on, the discovery and pairing process takes less than ten seconds. In terms of preferences, you can toggle between feet and meters as your measurement of choice, and whether or not you want the sound on or off. That's it.

By the way, in addition to smartphones and watches, the Trek CarBack Radar also plays nice with many of the best GPS sports watches available.

Installing the device on your seatpost is also a breeze. A built-in rubber strap and buckle system accommodate a wide range of seatpost diameters. There's also a second plastic hook and band to ensure it's extra secure.

3. No false positives

Trek CarBack Radar Rear Bike Light shown mounted on the seat post of a green bike with green foliage out of focus in the background
Trek CarBack Radar Rear Bike Light shown mounted on the seat post of a green bike with green foliage out of focus in the background

While testing the Trek CarBack I rode along both city streets — mostly unprotected bike lanes — and on designated bike trails. I also rode along several residential streets with cars parked on either side. At no point did the device alert to any false positives in any of these scenarios.

The cyclists, joggers and scooters I encountered along the bike trail didn't register, nor did parked or stationary cars pausing at stop signs. That said, there were several occasions when a steady stream of cars crept up behind me and I can't say for certain whether the CarBack registered them all.

I occasionally got the sense that the last car in line was going undetected. However, more testing is necessary to confirm this.

Trek CarBack Radar Rear Bike Light in someone's hand with the red light glowing brightly against an orange background.
Trek CarBack Radar Rear Bike Light in someone's hand with the red light glowing brightly against an orange background.

4. Audio alerts auto-silence in traffic

Speaking of heavy traffic. In the situation I described above, the Trek CarBack is programmed to pause audio notifications when more than three cars are detected. This saves you the annoyance of non-stop and unnecessary dinging in your ears.

However, once a caravan has passed, audio signals return in the form of the upbeat all-clear ding-dong.

5. It's also a high-power tail light

The Trek CarBack bike radar shown mounted on the seatpost of a green bike.
The Trek CarBack bike radar shown mounted on the seatpost of a green bike.

In addition to car detection, the TrekCarBack is also a super-powerful rear tail light with four flashing modes and 7+ hours of battery life, even when using car detection. Trek says it's visible up to 1.2 miles away, even in daylight, which puts it up there with some of the best bike taillights we've tested.

Though my initial impression of Trek's car radar by cyclists is positive, I'm still curious to see how it performs at night as well as in inclement weather where visibility can be a factor. I'd also like to test the Trek CarBack Radar Rear Bike Light head-to-head against the Garmin Varia.

Until then, wear your helmet and stay alert!

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