Crash detection for cyclists: an honest look at your options

How crash detection works, and why it misses things

Every option below works roughly the same way. Motion sensors (an accelerometer, often with a gyroscope) watch for a sudden spike that looks like an impact, and then the device checks whether you stay still afterward. If both happen, it sounds an alarm and starts a countdown. If you do not cancel in time, it sends an alert. Our explainer on what crash detection is goes deeper on the mechanics, and fall detection covers the closely related watch feature.

That design has two built-in weaknesses. A slow tip-over at a stop sign or a crash into soft grass may not produce a big enough spike, so it gets missed. And a hard pothole strike, a dropped bike or a fast gravel descent can look like a crash, so it false-alarms. Makers tune for this, but they all say plainly that their feature cannot catch every incident. That is not a reason to skip crash detection. It is a reason to pair it with a plan that works even when the sensor misses: a Guardian who knows your route and when you should be back.

Bike computer incident detection (Garmin Edge and similar)

Many riders already have crash detection without knowing it. Garmin's Edge bike computers include a feature called incident detection. According to Garmin's Edge 1050 manual, when the unit detects an incident with GPS on, the Garmin Connect app on your paired phone can send an automated text message and email with your name and GPS location, if available, to the assistance contacts you set up. You get a 30-second window to cancel if you are fine.

Garmin is careful about the limits. The manual describes incident detection as a supplemental feature, available only for certain outdoor activities, that should not be relied on as a primary way to get emergency help. It needs your phone paired, with an active data plan and network coverage, and your contacts must be able to receive text messages. Garmin also states that the Garmin Connect app does not contact emergency services on your behalf.

The appeal for cyclists is that the sensor rides on the bike you are already using, and the alert goes to people you picked. Garmin also offers LiveTrack for sharing a ride as it happens; our Garmin LiveTrack comparison and how to share Garmin LiveTrack cover that side.

• Alerts: your chosen contacts, by text and email, through the phone app
• Emergency services: not contacted
• Needs: a compatible unit, a paired phone with data and signal, contacts set up in advance
• Watch out for: a phone left behind or out of battery means no alert

Smartwatch fall detection (Apple Watch and others)

Apple Watch has Fall Detection on Apple Watch SE or later, Series 4 or later, and Apple Watch Ultra or later. Apple's support page says that after a hard fall the watch taps your wrist, sounds an alarm and shows an alert. If it then detects that you have been immobile for about a minute, it starts a 30-second countdown, still tapping and sounding the alert, and then calls emergency services automatically. After the call it messages your emergency contacts with your location. You can set it to always on or only on during workouts, and Apple turns it on automatically for people who entered an age of 55 or over.

When Apple released watchOS 8, it said fall detection had been tuned to recognize the motion and impact of falls from a bike during workouts. That makes the watch one of the few mainstream options designed to call emergency services directly after a cycling fall. Apple is also clear that the watch cannot detect all falls, and that high-impact activity can be mistaken for a fall.

Two practical notes. The watch has to be on your wrist, with Fall Detection switched on and emergency contacts set in Medical ID. And the call needs a connection: Apple lists a cellular connection, a satellite connection, or Wi-Fi Calling through the watch or a nearby iPhone. A GPS-only watch with your phone left at home, or a valley with no coverage, can mean no call. If you ride remote roads, read how to stay safe gravel cycling with no cell service before you rely on any of these.

• Alerts: emergency services first, then your emergency contacts
• Needs: a supported watch, worn on the ride, and a connection
• Watch out for: false alarms on rough roads; cancel promptly if you are fine

Phone crash detection is built for cars, not bikes

Newer iPhones have a feature called Crash Detection, and it is easy to assume it covers a bike crash. Apple's own support page says it is designed to detect severe car crashes, such as front-impact, side-impact and rear-end collisions and rollovers, involving sedans, minivans, SUVs, pickup trucks and other passenger cars. It is not described as a cycling feature. A fall from a bike is a different kind of event, and you should not count on your phone's car Crash Detection to notice it.

We cover this in detail in iPhone crash detection for runners and cyclists and in the short answer to does iPhone crash detection work while running or cycling.

Helmet-mounted crash sensors

A third category is small sensors that attach to a helmet, or that some helmet makers build in. Because they sit on your head, they can register an impact to the helmet itself, which is the thing you most want noticed. In general these sensors connect to an app on your phone over Bluetooth, and when they register a likely crash, the phone sounds an alarm and counts down before messaging the contacts you chose.

Products in this category change often, and features differ from one maker to the next: how long the countdown runs, whether contacts get a text or an app notification, whether the sensor needs charging or a coin battery, and what happens with no signal. Read the maker's own current documentation before you buy, and ask the same questions you would of any option in this guide: who gets alerted, does it contact emergency services, and what does it need from your phone.

• Alerts: usually your chosen contacts, through the phone app
• Needs: the sensor on the helmet you are wearing, charged, and your phone nearby
• Watch out for: a sensor moved to a new helmet and never re-paired

Holler's crash detection (beta)

Holler has an opt-in crash detection beta. When it is on, a possible hard fall or crash followed by stillness starts an "Are you OK?" countdown. If you do not respond, your Guardians are alerted with your location by email and app or browser push. Your Guardians open your live link in any web browser, with no app or account, so they can see where you stopped.

The limits are real, and we would rather you know them. It can miss real crashes and it can false-alarm. In a phone browser it only works while the Holler page is open and the screen is on, which is not how most people ride. The iPhone app is in private beta. Holler does not contact 911 or emergency services; your Guardians are the ones who act, and they call 911 if they cannot reach you.

Because of those limits, the most dependable Holler features for a solo ride are the ones that do not depend on sensing the crash at all. A return time sends your Guardians an overdue alert if you have not checked in five minutes after it, even if your phone app is closed. An optional stationary alert asks "Are you OK?" if you stop moving for the time you choose and alerts your Guardians if you do not answer. Our explainer on overdue alerts covers why a deadline catches problems that motion sensors miss.

Choosing, and combining, the right mix

There is no single best option, because the right one depends on what you already own and how you ride. If you ride with a Garmin Edge, turn on incident detection and make sure your contacts are set. If you wear an Apple Watch, check that Fall Detection is on during workouts. Either way, add a second layer that does not depend on detecting the crash: a live location link and a return time.

The table puts the four types side by side, using each maker's own documentation.

Layers help because each one fails differently. A watch can miss a slow fall, a bike computer is useless if your phone is dead, and a Guardian cannot help if nobody told them when to worry. Together they cover more of the gaps. For the full picture of riding alone, including route choice and what to carry, see the solo cycling safety guide, and if the worst happens, what to do after a bike crash.