Rear-view mirrors are important safety tools, but [Mike Kelly] observed that cyclists (himself included) faced hurdles to using them effectively. His solution? A helmet-mounted dual-mirror system he’s calling the Mantis Mirror that looks eminently DIY-able to any motivated hacker who enjoys cycling.
Carefully placed mirrors eliminate blind spots, but a cyclist’s position changes depending on how they are riding and this means mirrors aren’t a simple solution. Mirrors that are aligned just right when one is upright become useless once a cyclist bends down. On top of that, road vibrations have a habit of knocking even the most tightly-cinched mirror out of alignment.
[Mike]’s solution was to attach two small mirrors on a short extension, anchored to a cyclist’s helmet. The bottom mirror provides a solid rear view from an upright position, and the top mirror lets one see backward when in low positions.
[Mike] was delighted with his results, and got enough interest from others that he’s considering a crowdfunding campaign to turn it into a product. In the meantime, we’d love to hear about it if you decide to tinker up your own version.
You can learn all about the Mantis Mirror in the video below, and if you want to see the device itself a bit clearer, you can see that in some local news coverage.
I don’t wear a helmet when cycling but I was thinking about a sort of similar solution for riding a motorcycle, by having some tiny high def screen connected to a camera on the back of the helmet, powered by a flexible solar panel I can attach to the helmet somehow. I mean, I already got solar powered speakers built in, why not this?
There’s ben a few helmets with built-in HUD type systems, but the issue always comes down to focusing – the eye can’t keep the screen and the distance in focus at once, and switching between the two takes time. The idea always seems cool though. I thikn one of the more successful systems just used a few lights to indicate different things so they didn’t need to be in focus to convey a message.
I do move around a bit on my motorcycles but I don’t think it’s anywhere near the amount of range of movement cyclists go through on proper road bikes.
Ideally a HUD system should have its focal length set up so that the virtual image is in the same visual distance as whatever else you are focusing on, so that you do not have to change focus. A bit like a reflex sight on a rifle or telescope
very difficult to achieve in real life. I tried an after-market hud on my car for the last 10 yrs and it was never quite right. The typical focus distance varies with the speed and conditions. At 100kph it needs to be 50/100m in front of you. for town driving, not so much.
I concluded that a set of 5 or so led’s on the driver pillar showing which speed zone you’re driving would probably be productive. I don’t need to know my exact speed, just what zone i’m in. I can spot that in my peripheral vision.
HUDs have another major issue: processing lag. By the time the camera has captured the image, processed it, buffered it, transmitted it, the display has received it, buffered it, and draw it on the screen, and you’ve managed to react to the image, you might have half a second of lag. If the object is coming at you at 10 m/s (36 kph) it will actually be 5 meters closer than you think it was.
If it was another cyclist you wanted to avoid, that reaction lag can mean they’ve already run into you just as you started to turn away.
Also, the effect of seeing the scenery in front of you turn immediately as you turn your head, but the view back turning with a 200-300 ms lag will induce nausea in many people.
People get sick wearing VR goggles viewing virtual images, and with a camera in the loop it gets worse because the camera introduces extra lag.
Which is impossible because the distance to objects varies. The common textbook wisdom says that the human eye turns to infinite focus after 2 meters, but that’s actually not a hard cut-off. The difference in focal length simply gets smaller and smaller with distance until the eye can no longer make such fine adjustments or it runs out of adjustment range, which for normal healthy vision can be up to 100 meters and for far-sighted people even longer.
https://www.physicsclassroom.com/Class/refrn/U14L6c.html
The brain also uses the eye’s focus to judge distances among other cues like the size and parallax movement of the object. For a HUD, you have everything at a single fixed focus at infinity, which makes it harder to judge distances in the intermediate range from 2-20 meters behind. It actively messes up your brain when the object seems to be at a further distance by focus but closer up by the other cues.
I get that and you would need a very wide angle lens on the rear view camera for it to work. I think a wide screen so you can actually look at it with both eyes would be the best option.
I mostly want to know how close the car is and what kind of car it is. Is it a normal car, cop car, ambulance.
i do wear a helmet, but almost exclusively because that’s what my rear view mirror is attached to. the increased situational awareness is literally habit forming — i’ve found myself glancing up and to the left for it while walking around on foot.
as for the camera-plus-screen solution, might work, but i’d be leery of that much extra weight on my head and neck. maybe i’m just overly sensitive about that, though. i also wonder if flexible solar panels in that size range would provide enough wattage to power the screen? it’d need to be pretty darn bright to cope with sunny days.
Yeah, when you have a rear view mirror you want it all the time. You can get eyeglasses with a partially silvered spot at the edge of your field of vision, but that doesn’t work as well for me because it’s too close to my eye. About 4cm out in front of my eye is perfect, which means helmet or a clip-on to glasses.
There’s a helmet called the Reevu which has a series of prisms built-in and a window on the back of your head to give you a no-electronics no-lag rear view mirror.
https://twistingthewick.wordpress.com/wp-content/uploads/2013/06/vkt.jpg
Whether or not that prism gets shoved into your brain if you have a crash.. I do not know. I assume there is some kind of compromise trading a bit of crash ratings for situational awareness, but I could be wrong.
Oh nice. Good reviews too!
I don’t know regarding the crash part but I assume it’s safe. If this was a system helmet instead of an integral, I’d save up for it.
After what happened to Michael Schumacher I would be a quite wary of placing straight stalks on a helmet to hold things. Perhaps if they were curved and made from a semi flexible material and fixed at the back then the chance of injury from the helmet attachments themselves would be reduced.
Schumachers injury had nothing to do with any attachment
I’m guessing he means Senna – 31 years ago today. Saudade.
No.
Everything.
His camera mount was far too strong.
Got pounded into his brain by the ‘magic angle’ impact.
how did you come up with that theory?
Not a theory.
German news.
Confirmed by German MDs/F1 fans in family.
The Schumacher family aren’t at all happy about details being shared, but it’s the fact.
Bur does it make the helmet less effective in a crash?
Completely depends on who you ask. Lightweight stalks like this would just break away.
Break away… right INTO YOUR EYE! OK, jokes aside.. I have been using a mirror on my helmet for over 20 years, and it is fabulous. I wouldn’t recommend it when racing, but for touring and casual riding it is fantastic. There was a company in the 70s that made them, and then vanished. Around 2000 they resurfaced for a while, but I think they are gone again. Being able to tilt your head just slightly to see what is happening behind you is fantastic, and frankly, I don’t feel the need for a second mirror at all. A simple twist of the neck and you can see EVERYTHING. The only problem with the mirror is that when it is on the helmet, you can only use it with one eye. The second eye has to be trained to mentally blend out while looking at the mirror, because the images are simply too differnet for the brain to make sense of them. It takes about a week, and then you don’t even notice it happening. I highly recommend this to anyone on a longer tour… along with the shimano sandals with the cleats. SH-SD5 (they run small, so order one size larger!)… they will really change your life. :D
SPD sandals are ridiculous. Get wooden clogs with SPD’s. At least they stay on your feet when you have to bunnyhop a downed rider.
I can generally hear a breakaway behind me, but the mirror is nice in crits because it lets you see when someone’s not holding a line in a turn and you’re about to get hit.
I’m honestly confused as to why anyone would need two mirrors, but apparently I ride very differently than the person who built this. I’m always looking at the same place, about 8 meters ahead of me, regardless if I’m sitting upright or out on the aero bars. As a result, my helmet’s always at the same angle and the only difference in what the mirror shows is because it’s lower than it used to be. Same field of view. But clearly other people don’t ride like that, which is kinda interesting. Different styles, different tools.
The answer to that is obviously yes it could, but really that isn’t the question anyway – the question should be ‘Does the added risk of this in an accident matter more than the benefit of having it?’
I’d suggest as long as you do something like this well so the attachments can never be driven through the helmet like a spike, don’t interfere with the crumple zone energy absorption and are able to break away or bend when subjected to forces long before they would put your neck at risk its a clear winner. You still could have that 1:1000 accident profile that means it breaks in a weird way and does drive a shard of the mirror into your throat or something that a regular helmet couldn’t do to you, but you’d probably be much less likely to get into an accident for having it…
The way I mount the mirror, there’s absolutely no way an accident could drive it into my eye; but of course the whole reason it’s there is to prevent the accident anyway.
The real question is whether the improved awareness makes a crash less likely enough to offset its reduced performance as a crash helmet. Nothing in life is free
Bike helmets save lives…one did mine. I hit a kangaroo at ~32km/h, flipped over the handlebars, and landed on my head and shoulder. Helmet did what it should, took the brunt, and split into 3 pieces. Nasty big stone embedded in the dense foam over my vulnerable temple. Shoulder won’t ever be the same (gruesome details omitted), but alive I am.
Same. I went through the passenger window of a car that right-hooked me, and it tore my left earlobe off but the top of my head, the stuff covered by helmet, was untouched. I went through the windshield of a car that ran a red light, and again, the helmet-covered stuff was uninjured. When I’m racing mountain bikes, I wear a full face helmet, because broken jaws suck, and I go through about one helmet a season because I slam the chinguard into a rock. Helmets rock.
I hope they managed to sew your earlobe back on, smellsofbikes. Yes, cars seem to be the natural enemy of bicycles. I sure wish more of the new e-scooter crowd would take the hint. Bell helmets, guys. That and some lights, or at least reflectors. Pet dislike is an invisible e-scooter at night, coming head-on at ~40km/h, on a poorly lit, all-too-narrow bicycle path. I’ve had enough of operating tables, and tiresome months full of plates and screws.
Yeah, it has an interesting scar and fold in it, but it’s reattached and only looks kinda weird.
I commute all the time, on very busy highways, so I get way more than my share of car interactions. Bell helmets are my favorite, in bike, motorcycle, and car racing. I don’t have actual data to show they’re superior. It’s mostly just gratitude for how many times they’ve been between some object and my skull.
I have a couple of 15cm long scars on my head from a car crash where I wasn’t wearing a helmet, and I sure wish I had been!
The issue is that you have to share the road with cars, so you have to go fast to keep up, which means riding bikes with low handles that put you into that superman position all ready to headbutt the pavement.
Bike helmets’ protection is exaggerated. Bike helmets don’t give the protection of a motorcycle helmet. People break a helmet and then say, “That helmet saved my life!” Probably not true. According to cyclehelmets.org, if it broke, all it means is that it failed, especially if you don’t see any compression of the foam. That’s not to say you shouldn’t wear one; just keep things in perspective.
The greatest danger in city traffic is the intersections, and one of the dangers is that drivers, perhaps on the phone, are not thinking about what they’re doing when they plan to pass you and then immediately turn right. With a mirror, you learn to predict it and use a combination of hand motions (not insulting!) and your positioning in the lane to get their attention and prevent the accident. I give them room to pass on the right, then wave them by to make their right turn. They don’t understand how I can see them, but they appreciate that I’m looking out for everyone’s safety. Also, sometimes the best course of action to handle a situation developing up ahead will depend also on what’s behind.
If your bike helmet broke it definitely did something to dissipate the energy – as that is what breaking functionally is a consuming of the impact energy into breaking the thing that isn’t your head. It probably shouldn’t do anything but crumple, but still…
Not necessarily by much. Foam isn’t that difficult to break.
The other thing is that people wearing helmets sometimes trust the helmet too much and actively headbutt whatever it is they’re hitting instead of trying to turn away. With minor crashes at low speeds, you usually have the time to react, but people wearing safety gear just brace back and hide behind the cap.
Ok, in my crash, in which I broke a helmet upon sliding and impacting a curb head first, I can 100% say with certainty the helmet either saved my life, or at a minimum turned a potentially life altering concussion into something I could walk away from. I don’t know why people are anti-helmet. It’s cheap insurance, and I feel naked without one anyway.
It’s not so much being anti-helmet, but being anti helmet-laws where people are forced to wear one.
I’ve personally taken the time to look through the statistics, the use cases (driving situations, type of driver, conditions etc.) and concluded that the risk of me getting into such a serious accident AND coming out much worse for not wearing a helmet is low enough that I simply don’t want to bother.
The major contributors in that decision were: not riding among cars, not riding at excessive speeds, and not cycling while drunk. Those three took the risk of accidents down by 80-90% and the consequences of the accident were significantly less severe as well. The most likely outcome of a cycling accident for me is breaking a wrist after a minor spill.
If I remember correctly, the outcome of the calculation was that I’d have to run into a serious bike crash (ending up in the hospital) 12 times before I had a 50% chance of receiving a serious head injury even if I never wore a helmet. I’ve never had such an accident, and by my riding habits there’s a great chance I never will.
Maybe when I start to get old and frail I’ll start wearing a helmet, but so far I simply don’t see a reason.
Having found that article on cyclehelmets, https://www.cyclehelmets.org/1209.html if anybody else is interested I’d have to say its rather lacking, focused only on life-threatening and seemingly only brain injury reports and expecting the helmet to always crush in every collision – which obviously you shouldn’t expect as there are so many angles of impact, your neck is flexible etc etc. But it likely would be doing its job in many of those cases without crushing – just in this case it is spreading that initial impact out across your skull, so your head skates off that sharp corner instead of gets mashed by it or runs more freely across the road surface so it won’t grab and twist your neck or simply preventing serious lacerations etc that might be survivable but are quite possibly life limiting – you can live with half your face torn off if you don’t die from the infections, but even now there is limit to reconstructive surgery (and in many places could you even afford it?).
Or stating rather confidently in the case of oblique impacts that “However, if the impact occurs without any compression of the foam, it suggests that most of the force was parallel to the surface of the helmet and not directed towards the head. As the surface of a helmet is some small distance from the surface of the head, again the wearer may have suffered no injury at all if a helmet had not been worn.” Which is technically possible but really doesn’t take much thinking about to debunk as stupid reasoning – as managing to have a near miss so close to your head it would only every have hit your helmet with great enough force to crack it is not something a cyclist would ever choose to risk – nobody deliberately lets anything that could be dangerous even remotely that close to their head. So with that helmet there to push your flexible neck aside when you do have that accident odds are really really quite good your head would have passed through the same space as the object that cracked the helmet had it not been there – as for you to have let anything get that close in the first place you are almost certainly falling off…
And the few statistics brought up fail to really account for anything more than looking for a way to make the data match what they want it to it seems. Not saying they don’t have some good points too, but taking the Aussie case making cycling alot less enjoyable in the heat over there so everyone is driving instead of cycling and the results on the remaining cyclists are expected – more big metal boxes on an unchanged road network means more drivers that will not give the cyclists the attention they deserve if they even notice them with the massive increase in other large metal boxes moving around commanding their attention… A well documented effect that more cars equates to more injuries for the folks not in cars around the roads that isn’t considered at all, and likely dominates the reason for the changing cyclist injury rate.
I’ve had a couple minor slips over the years where I landed on my back or on my shoulder from riding height, where my head got close but not touching the ground because I was bracing for the impact and tucking in. A helmet in between would have hit the ground, though, and resulted in a “life saving” effect where the helmet actually strikes my head and causes the whiplash effect on my neck.
To illustrate the effect:
Sit on the floor and tuck your chin to your chest, then push yourself to a backwards roll until your shoulder blades hit the ground and your head stays up off the floor. That’s the typical case I’ve had where I’ve slipped on ice, the bike does a 90 degree flip under me and I fall down backwards.
Now imagine you’re wearing this (a big lumpy helmet extending backwards off the head):
https://cdn.thewirecutter.com/wp-content/media/2022/04/bikehelmets-2048px-0243-1.jpg
Put your closed fist behind your head and repeat the exercise. Did you just punch yourself in the back of the head? I did. It hurt. If I were wearing the helmet I would say “whoa, that hurt and my neck is now sore, I’m glad I was wearing a helmet”.
@Dude that is a very different type of accident to the one described though, and wouldn’t break the helmet in the manor described either – you might manage to hit hard enough to crush or scrape the foam a little bit but its not the cracking etc they were talking about, and if you were going to hit hard enough to smash the foam you definitely would be hitting your head anyway – might not be hitting your head hard enough to actually cause real harm without the helmet, but the odds shift towards concussion being quite likely – these crash helmets are not really spongy they take quite a hit before anything really happens to them, as they are meant to absorb the big impacts gradually enough to be survivable, not the already very survivable hits to be as comfortable as possible…
As I said though that article isn’t devoid of all merit, and neither is your point as its absolutely true you could just about manage an impact the way you describe where the helmet touches the ground enough you actually notice but you were not about to brain yourself – but its quite clear in that article they are looking only for the cases and selectively using data to match their desired outcome. If you want to discuss the safety of helmets and the flaws in a way that actually means anything you have to consider a much wider dataset than just looking for traumatic brain injury from a bicycle accident etc.
Maybe, but it’s also very common. The point is, helmets are supposed to smooth the impact and reduce rapid head movements, but in some cases, especially in minor accidents they can also cause rapid head movements by hitting objects you’d otherwise miss. The added mass on the top of your head makes your head swing around slightly more when you’re thrown to the ground, which increases the chance of a head impact together with the added size of the helmet.
Also, foam helmets aren’t necessarily tough. The foam itself is quite brittle and it’s the surface plastic veneer that keeps it from crumbling up just by handling it. That’s why the better helmets have an impact resistance plastic outer shell and foam and padding inside instead of the cheap all-styrofoam helmets which are just placebo.
Never ride a bicycle on open roads, heavy traffic roads and the like, no helmet nor mirror can save your life.
I only ride on cycle paths and fortunately there are plenty of them in Europe and especially in my area. Most people here ride with helmet on.
Furthermore, it seems that road accident statistics in the USA are quite disastrous compared to Europe (without any intention of being controversial), so better for the former colony’s biking friend to be very carefull !
that depends entirely on the road; route selection is crucial in road cycling.
sure, there are definitely roads that would be suicide to ride a bicycle on. but then there are plenty that are quite safe, too. personally i like small backcountry lanes, farm-to-market roads, and narrow hilly/curvy secondary roads; ones with low and slow-moving traffic. selecting the right time of day and week helps a lot with this, also.
my partner, on the other pedal, insists on roads with wide paved shoulders and has a much higher tolerance for high traffic speeds and volumes than i do. i suppose the road shoulder is the same width at all times, so there’s that.
technology can help, and a mirror is one thing i would personally strongly recommend. as i mentioned earlier, they’re absolutely habit forming. i’ve not personally tried the rear-facing radars some ride with, but i imagine they can give good warning too — not sure if they’re worth their fairly high price, though.
what one can’t do is blindly ride the same roads and routes on a bicycle as one would drive in a car. frequently, going quite far out of one’s way to avoid certain spots and roads is the only sensible thing. but if you’re really in a hurry, you’re probably not pedaling, right?
One man on a forum showed off his radar which told when a car was coming; but here in southern California there could be cars as far as the eye can see, and if every fifth one is farther to the right than is safe for you, your radar won’t help you one bit.
I could describe many other scenarios; but a serious one I’ll mention is that on a curvy mountain road I was climbing, there were lots of people going up to a lake for a vacation, some with boats on wide trailers, and they’d forget that just because the tow vehicle would clear you didn’t mean the trailer’s right wheel and fender wouldn’t kill you; and also people who had rented RVs and didn’t realize how much width they take up on the right, especially in tight turns! I’d be dead without a mirror. As they were coming, I often had to move a little to the left and urgently motion with my arm, “Don’t pass now!!”, then get around a turn and into an area that had a little more room, and wave them by, “Now pass!”
And as others have said, yes, even when just walking, I instinctively look in a mirror that’s not there.
I don’t seem to have any need for two mirrors though. Whether I’m on the basebar or aerobars, my glasses mirror has the correct angle.
I’ve been riding with a Third Eye on my helmet for decades. Probably the two most important pieces of gear I use. I can credit the various Bell, Bontrager, and Giro helmets I’ve had with saving my life several times. Considering what I ride, a Mantis would not be all that useful. But for a diamond-framer rider it likely borders on ‘shut up and take my money.’
Mirrors are required by law for every other vehicle. I think they should be required for bikes, too. I could say I don’t know why people ride without them, but I used to be one of them, until I got rear-ended, which convinced me to get a mirror. (Fortunately I was not hurt.) I’ve ridden nearly 100,000 miles since then, and yes, I can definitely say the mirror has saved my life many times. A helmet can give a little bit of protection in an accident, but it cannot prevent accidents like a mirror can. Non-users think their hearing is good enough. If they’d just get a glasses mirror and learn to use it (which takes time), they’d find out how blind they had been. Also, sometimes the best course of action to handle a situation developing up ahead will depend also on what’s behind.
That “accident” at 30s into the video is mind boggling. Somebody should tell those cyclists that it’s not safe to cycle on the highway. No matter whether you have a helmet, mirrors or stick out your arm, speed differences are simply to big, and you’re never going to win from a 40 ton truck. So shame on those cyclists for giving that truck driver a heart attack.
…i’m struggling not to flame you for that comment.
let’s unpack those few seconds of video.
firstly, a highway that heavily trafficked with such fast moving vehicles would absolutely fall under my own personal definition of “suicide to ride a bicycle on”; i can’t fathom what those two cyclists were thinking riding it. everything else i’m about to say should be filed under that heading, but even so…
from what little the video shows, that stretch of highway seems to have wide open sightlines. unless there’s some really creative video editing going on, that truck driver had to have been able to see them there from well away. they should have been, to him, an obvious and effectively immobile obstruction in the road — something every driver needs to watch out for anyway, as you never know when there’ll be an engine block in the traffic lane having fallen off somebody else’s truck.
being able to, if need be, come to a complete stop for random roadway obstructions at no notice is every driver’s responsibility. yet he chose to pass them at high speed, on the right, without giving adequate buffer space or warning. and they were human beings in the road.
it absolutely matters not in the slightest that they, arguably, shouldn’t have been riding there. the trucker had a positive responsibility to NOT RUN THEM OVER, and failed. at that point, my sympathies for the trucker run mightily thin. and my sympathies for you, whose priorities seem so badly skewed out of proportion, are… thinning.
First, thank you for your self control. My previous statement is also a (smal) part of my opinion, and partly meant to make a controversial statement to shine a spotlight on the “other side” of what the video was intended to purvey.
Truck drivers also have a responsibility for not driving over people when driving / parking backwards, and yet we all have to put up with mandatory beepers for the rest of our lives. These beepers are mostly an evasion of responsibility for truck drivers, but in pracktice they also save lives. But imagine living in some place where you hear 30 of those things each day. I’m overly sensitive to some sounds, and that would really drive me nuts. I’m also quite flabbergasted about why it’s allowed for trucks to have “dead angles” in a time that a camera system costs less then 0.5% of the cost of a truck, so please don’t get me started on that topic.
For what the truck driver should or should not have anticipated, there is not enough info in that short clip to draw any conclusions.
For a real (my only?) conclusion, showing the accident in that clip about rearview mirrors for cyclists does not help it’s cause. I watched the 10 or so frames of the accident around 10+ times to try to see what was really going on, then could not correlate it to the rear view mirror thing and did not see the rest of the video.
Luckily Clint Eastwood already know the worth of an opinion before the Internet even existed.
Possible they had no choice at all – if the road between A and B is that road and even worse options to cycle on… Also not entirely sure what that road is, or where it is. It does look from that short clip like its a road bicycles wouldn’t be allowed on here though that is far from definitive as it could be a perfectly normal to cycle on pretty slow road quite easily. Also your local laws undoubtedly vary (and from that clip it really isn’t clear what sort of road that really is – for instance near me there are roads that look very like that and you are absolutely meant to be able to cycle on, and will if you don’t know the road get suckered into thinking its a good choice as when you get to the industrial estate and shopping centre the previously normal small road grows heaps of extra lanes for not very long at all).
Though even if it is a road the cyclist definitely has no right to be on, I agree there is no way that truck driver is driving in a safe manner… Which does sadly seem to be from my personal experience a common occurrence with ‘professional drivers’ other than the bus drivers – for example at a roundabout right next to the railway station I clearly had right of way being already on the roundabout, watched the driver of HGV that could still have slowed/stopped spot me and clearly I’d be in the way by the time he gets there but, instead of slowing down they speed up even more… Saw it coming because paranoid alert level is just how you have to cycle here and jumped the bike up onto the centre of the small roundabout, but it was still pretty close…
Bus driver on the other hand around here do tend to be exceptionally courteous, at least if they did see you – can’t blame them if you arrive in a spot they don’t have good visibility etc.
For me it started with a little binder clip and a dental mirror in the 70’s much later I made a stiff wire and mirror clip on my glasses and I never take it off. I still get asked “is that Google Glass?” First off it’s on the left not the right I explain, it lets me make left turns (US) and cope with denser traffic. They have head aiming of small guns from inside of an armored carrier and I get a head stabilized full lane width shot out the back at half a block distance by looking 10 o’clock high. Always in the same place the stiff springy wire insures that it never is off aim.
I installed a rear view mirror on my cargo bike and never looked back. Well that’s a lie actually.
I just use my Garmin radar, like everyone else I know.