Bike accessory leaves a trail of chalk behind you

Bikes Fun & Games
Bike accessory leaves a trail of chalk behind you



Contrail is a device that applies chalk to the rear tire of your bike, leaving a trail behind you. It leaves trails for motorists and other cyclists to see, enabling bikers to “reclaim this crucial shared space.” I’m not sure where you can get one or if it’s even been physically realized, but I like the idea. It’s like a cross between the prototype for the projected bike lane symbol and Bikes Against Bush, which sprayed chalk according to text messages. Via Cool Hunting.

138 thoughts on “Bike accessory leaves a trail of chalk behind you

  1. skyler stoudt says:

    I think this is perhaps one of the coolest things i have seen before but i can’t help but think somewhere somebody is gonna get pissed off and report this as graffiti

    1. scarr says:

      i agree completely.

      awesomeness, but some stick, will complain (as his kids draw on the sidewalk)

      think about the good it would do:
      “oh i am coming up on a bike”
      “hey this bike lane gets alot of traffic”

      ect ect

  2. Betty Rae says:

    I don’t think it would be classified as graffiti because it will wash off with rain. They would probably have to come up with a specific ordinance, if they chose to pursue it.

  3. Pelrun says:

    Ahem, “reclaim this crucial shared space”? Like it was theirs to begin with? And they no longer wish to share it?

    1. Saffleur says:

      Considering the bicycle came before the car yes it was “their space” to begin with.

      1. Jim K. says:

        This gives me an idea. Since horses and buggies logically came before bicycles which came before cars, I think I’ll adapt one of these for a buggy. Lookout world, I’m taking back the streets!

      2. Anonymous says:

        Remarkably (and surprisingly even to me), you appear to be incorrect.

        The earliest bicycle was a wooden scooter-like contraption called a celerifere; it was invented about 1790 by Comte Mede de Sivrac of France.

        The first self-propelled car was built by Nicolas Cugnot in 1769 which could attain speeds of upto 6 kms/hour.

        so uh. Yeah.

        1. Anonymous says:

          There was actually a spring powered “car” invented by Archimedes back in the ancient times. Too bad the Greeks didn’t take it seriously.

        2. sourpuss says:

          wow guys do you spend every hour of your life, clarifying different facts, and proving people wrong, and commenting on things like this? its a cool idea, but you dont need to like start a lawsuit.

  4. Trevor says:

    Yeah! That’s so cool!!! I so want one. Silly, I know, but still, its fun.

  5. pacute says:

    maybe this will start of a new kind of art…. Bike portraits?………


  6. John Doe says:

    This would be perfect for me as a stalker. It would be much easier to follow the kids home.

  7. Anonymous says:

    i think it’s bloody stupid, you just end up dirtying the place leaving it for someone else to clean up. they may call it chalk but who has confirmed it is not toxic? these kinds of gimmicks are clearly for the cognitively disabled.

    1. Jo says:

      “i think it’s bloody stupid, you just end up dirtying the place leaving it for someone else to clean up. they may call it chalk but who has confirmed it is not toxic? these kinds of gimmicks are clearly for the cognitively disabled.”

      Chalk is Calcium Carbonate or Calcium Sulfate, doh…it’s found in the earth…it’s a mineral…and besides, things such as this probably have to be approved via EPA before they can be freely used in public venues…think a little it…

      “excellent! Chalk dust to clog up the bike mechanicals, another reason the knuckle-walkers will use to go after cyclists, defacing roadways, adding particulates to the air. This will definitely be additive to my life as a bicycling commuter…”

      …again…it’s Calcium Carbonate or Calcium Sulfate…and they’re not bike “mechanicals”, they’re bike mechanics…
      Before you complain of particulates being added to the air by harmless chalk, how about you think about the ones you’re contributing by wasting your time complaining about novel inventions?

    2. Anonymous says:

      Anyone concluding this as “grafitti” or “dirtying” obviously would prefer to just see the millions of cigarette butts and repeated trails of burnt rubber that now exist along our roads…

      Yeah we wouldn’t want to leave a colorful mark that’ll wash away on the first rain… that would be “ugly”.

  8. Anonymous says:

    excellent! Chalk dust to clog up the bike mechanicals, another reason the knuckle-walkers will use to go after cyclists, defacing roadways, adding particulates to the air. This will definitely be additive to my life as a bicycling commuter…

  9. Anonymous says:

    I can see both sides of this…the biker who want’s to make sure the perhaps ignorant driver behind him knows there are possibly a number of cyclists in front of him…the person who lives in a rural area and constantly sees these striped lines in front of his house either in the street or on the sidewalk…etc. Also, what about when it rains, these things can muck up the works on the bikes themselves if they are not so easy to remove from the bike. Are these things cheap and that felt wheel getting wet from wet pavement? Can you imagine wet pasty chalk all over your back or better yet, your bike?

    Ultimately though, the safety of the cyclist is the more important and it is up to them whether they want safety on their side, and to let drivers know to look out for cyclists on the side of the road. Oh, I can go on and on, but let me leave one thought, most drivers as it is, do not pay attention to the painted lines on the road anyway. You think they are going to watch out for these chalk lines?

    1. Rob M says:

      First of all, if it is daylight, they will see the bikers themselves, and know they are there.

      Secondly, if it is night, they won’t see the chalk at all, and it would not add to the safety of biking on the road. Reflectors on your bike, or on your person is much more effective, and adds much more to your safety than any chalk lines would.

      Third, even in the daytime, drivers won’t pay any attention to the chalk lines. There are plenty of people who don’t pay attention to traffic lights, lines already on the road, stop signs…etc.

      Maybe they would be fun, and kind of cool to use, but that’s about all that they are. They wouldn’t add to the safety of biking at all, and would be completely impractical on days where it is precipitating.

  10. AndyL says:

    Pelrun said : “Ahem, ‘reclaim this crucial shared space’? Like it was theirs to begin with? And they no longer wish to share it?”

    Believe it or not, but automobiles have not always existed. With the exception of the interstate freeways, The roads have *always* been shared space.

    Many people using the roads think that is it exclusively intended for their type of vehicle, therefore it must be “reclaimed” as shared space.

    Would it have helped if it said “The shared nature of the space must be reasserted”? That’s not quite as snappy.

  11. Matt Farley says:

    on a recent ride, one of the cyclist rigged up a bottle of paint to drip on the rear wheel. It left a faint yellow trail, complete with loops around each stop as he looked for a place to stop.


  12. b says:

    i’m not even a cyclist and i love this! i think people should just get renegade — every bike rider in every city, go put one of these on your ride.

  13. A says:

    That’s all I need is another gimmick on my frame. And I think I’ll keep friction between my tires and the road, thank you. The contact between tire/road is small enough, I don’t want chalk there! (And it’s a good thing that chicks helmet is clipped to her bag, pff, hipsters…)

  14. anonymous says:

    this won’t make you any less squishy when i run your hipster ass down…

  15. Interesting says:

    The only issue that I see is that it will probably spray up on your ‘behind’

  16. Jack of Most Trades says:

    When I first saw this I didn’t think much of it, but now that I see in the comments just how many people it’s pissing off, I have to declare that it is “Art”.
    Doesn’t really serve any useful purpose, it’s individualistic, and it arouses strong emotion in people.
    Yep, it’s Art.

  17. . says:


  18. a biker says:

    Whatever ideals of freedom lay behind this, the reality is that the cost of building and maintaining the roads is met in majority by the motorists, by registration fees/road tax and fuel taxes. Its like jumping into your neighbour’s back yard and urinating on their sycamore tree because the tree belongs to nature.

  19. icebiker3 says:

    It is just a single step up from a baseball card. So What? Something fun for your inner child to play with.
    …and could be a mess in the rain. I don’t see this lasting too long, not with how clean the bike lanes usually are. Another case for fenders.
    …Art. Art who?

  20. Chad says:

    I have to say I thought the idea was pretty neat at first but then I thought about it – if you have many of these devices all leaving a trail it’s going to be a potential saftety issue I think for cars and possbily other cyclists due to road markings potentially being obscured. And also it will add yet more distractions on the roads on top of advertising, street signs shops, pedestrians etc. etc.

    Another possiblity is that other riders and pedestrians will cop a breathful of chalk dust, which isnt harmful as far as I know but isn’t exactly pleasant (if this happens).

    So nice idea in theory but I don’t think they should be allowed to be used.

  21. Mr Fnortner says:

    When I drive my car I am leaving behind a stream of simple carbon, an everyday particle common in nature and vital to life. It is eminently biodegradable and recyclable, and washes off the streets, plants, and animals in the rain. I feel I am contributing to the health of the planet whenever I drive.

    The carbon dioxide my vehicle also produces is essential food for all plant life, without which the planet would wither and die. The further I drive, the more enriched the ecosystem becomes with this elixir of life. Verdant forests and lush green valleys are not the only beneficiaries of my travels. All human and other animal life depend on the this plant life for their very survival. Without this carbon-sustained plant food, we too would be dead. I am proud of my small contribution.

    1. Billdave says:

      In a high bike traffic area, just a big chalky mess until it rains again. safety? I’d learn quickly to ignore these marks which could have been laid down any time since the last rain. I’m not sure how leaving a chalk mark rates as “fun”, but hey, maybe I’m just a curmudgeon. To me it seems like an extension of the not always admirable human desire to mark up everything we touch and piss on every hydrant out of territoriality and ego.

  22. kapauldo says:

    I put up this poll: (linkback) Cool or Lame? Bike accessory leaves a trail of chalk behind you [VOTE] –

  23. Alex says:

    Fix the design and have the wheel turn the other way so the chalk doesn’t have to go _over_ the wheel :)

  24. Anonymous says:

    This looks really fun.
    But it’s going to have the opposite effect – it’s going to demonstrate how poorly bicyclists follow the rules of the road – the single biggest problem with the bicycle movement today.

  25. Rob Cruickshank says:

    Unfortunately, I can’t see this actually working well enough to cause the sort of grief that’s getting people worked up.
    I can’t see the feed mechanism working as advertised, and it simply doesn’t hold enough chalk. There’s a reason that creepy old guy who made the lines on your school’s football field had a big hopper full of chalk.
    Oh, and just to stir the pot, the whole reason roads got paved in the first place is largely due to the lobbying of cyclists in the late 1800’s.

  26. says:

    Forget the worries about the markings it makes on whatever roads:

    The device, if mounted as shown, could lead to its own demise or a sudden rear-wheel skid in the event it slips down the downtube.

    It needs to be on a spring arm and somewhere past the pinch point where the wheel rotation can’t carry it into the frame.

  27. Cyclonus says:

    I can just see people complaining about how their sidewalks are marked up. But I wonder if this will be allowed during marathons.

  28. AndyL says:

    Bizarre, irrational hatred of bicycles aside,

    Wouldn’t this represent a rather serious loss of traction?

  29. Thomas Anderson says:

    I heard the expression fixed gears are for assholes. But it turns out it’s for hippies. Roads were made for cars. Get over it.
    It’s a fun idea. But I can’t help but think that those few hippies are just cycling over their own paths to make it look busier than it is.

  30. Anonymous says:

    Many roads are maintained with taxes paid on top of the price of gasoline. If there is a bike lane, fine, use it. Otherwise expect to have people passing you in close proximity. It isn’t shared space…it was purpose built for motorized vehicles. And if you are a cyclist and you ride side by side….that is just plain dangerous. Single-file only and don’t whine when people pass you because you are going 5 mph up a damned hill. Chalk is for little kids on sidewalks and driveways.

    1. Anonymous says:

      That’s amazing. The roads near me were first made when there were about a dozen automobiles in the entire state, perhaps even in all of New England.

      Not all the streets this far from the downtown were paved, of course, but hey, with all the sand on the roads right now I think my bike would prefer a dirt road, and with all the potholes, I think my car would too!

      Anyway, sorry that everyone in the world doesn’t get out of your way when you need to go some place. We’ll try to do better in the future.

  31. Ben says:

    i would ride a pnus outside a mcdonalds

  32. Spitmonkey says:

    A rainbow bike lane, cool.
    But do you really want me to stalk you?

  33. alanbleiweiss says:

    Having lived much of my life in urban and suburban areas with the ever increasing paving of life, I think this is brilliant and a superb way to brighten our daily lives. Anyone who would think or claim this to be graffiti would have to be lost on a path of myopic thinking.

    Its like here in Marin County California – once a year they have a festival where an entire section of downtown San Rafael is closed off, the streets are freshly paved and artists, artisans and fun-minded people come out to create some of the most beautiful chalk-drawn art imaginable on those streets.

    With this simple device, so much positive could come…

  34. tremendous says:

    the weird bike hate on what you’d think would be an easy-going and friendly place full of makers is bizarre. I do not own a bike but I struggle to see what this is doing to make some of you turn into grumpy a-holes with a chip on their shoulder.

    oh riiight, you’ve not changed, you were always this way.

  35. nick says:

    enabling bikers to “reclaim this crucial shared space.” reclaim? it was and never will be theirs to claim, cyclists pay no road taxes and are a pain in the ass for motorists who pay to use the damn roads, and to be honest a shitty chalk line is not going to help reclaim anything.

    1. Anonymous says:

      And I quote from the wikipedia article on the bicycle boom:

      “Very quickly, the penny-farthing passed out of fashion, and multitudes of people all over the world began riding the “safety”. It was largely the popularity of this type of bicycle at this time which first caused roads to be paved.”

      Unless the roads in question are interstate expressways, they are shared space. No matter if there is a bike lane or not. Period. Respect the bikers and you will have respect given to you. Road taxes are only supply a portion of the money used for the roads, guess where the rest comes from… STATE TAXES. Your ignorance amazes me sir. And let me guess, you probably park in handicapped spaces and drive in bike lanes too? Why don’t you try it some time, you might lose some weight you stupid fat knob.

    2. hypatia says:


      First you have this implicit assumption that anyone who uses the roads for biking do not have cars and/or never use cars, and although it shouldn’t have to be said, this is completely faulty thinking.

      Then there is the assumption that “road taxes” somehow cover the amount of money need to build new and maintain road structures. This is also false in most if not all areas. Infrastructure has a very high cost and the money is pulled from many taxation sources along with grants and loans.

  36. Anonymous says:

    screw safety. i just looks damn cool.

  37. Izabela says:

    Is it going to create accident? Imagine you get onto such road and see those, what is your reaction?

  38. Matt says:

    I cant help thinking that putting chalk onto your bike tire might results in some negative side effects. Such as losing traction when cornering and subsequently falling off and looking not just like the tool who fell off his/her bike in a corner but the tool who fell off his/her bike in a corner whilst drawing pretty coloured lines with the back tire. Perhaps, like someone else who viewed this said to me, we should also add some form of oil and crushed up glass mixture to the gadget just to raise the bar little because we cyclists really dont have enough to keep us on our toes when on the bike paths. I know, lets get these onto 4WD’s also except have them dispense crushed up baby seals and bunny rabbits. What? Too much?

  39. Anonymous says:

    I like this. I can see a town giving out chalk to bicyclist for a study on land use. The town could see the chalk and use it as a way to improve high-traffic areas.

  40. Anonymous says:

    To be fair roads may have been paved initially because of bikes, but their main use now days is for cars. Lets face it, you don’t look both ways before crossing the road so you won’t get hit by a bike.

    Oh, and it is in fact annoying to come up on cyclists riding abreast of each other on a road with no shoulders and a high speed limit. But that was just my rant.

    As far as the chalk goes it does seem like it would cause more problems in the end. Including not holding enough, being a pain to maintain, and possible safety concerns. Never underestimate the power of stupid people in large groups. Blanket statement there, not specifically directed at cyclists.

    Lastly, at night you can’t beat the strobe light/ reflectors combo. That is by far the easiest way to spot a cyclist.

  41. grrraaahhhh says:

    fixies ar efor fixie tracks you stupid fucks
    get a real goddamn bike mother fuckers.

    1. Anonymous says:

      sorry. i guess i’ll stop riding my fake bike.

  42. NoBody says:

    Motorist are required to be licensed and to obey the law. Cyclist don’t have to have any do anything special. So it isn’t surprising that cyclist frequently don’t signal, come into the path of cars, forget reflective lighting and so on.

    It is no surprise that cyclist are hated when they frequently cause car accidents because of motorists doing the right thing. To cyclist: You are sitting on what equates to steel wire. Think about the two ton vehicle near you and how it is trying to make sure you aren’t a smear on the road.

  43. donna says:

    It’s chalk! what’s the big deal??

  44. meagan says:

    Speaking on the behalf of cycalists not all of us ride two by two and ignore traffic signs and neglect to signal. There are a few of us who know that we SHARE the road, I see no need for anyone to try and re-claim anything just a world that needs to learn to get a long. You can be neglectfull no matter what your mode of transportation, lets not forget about all the motorists who dont signal or abruptly change lanes and cause even more dangerous problems than a bike ever could. You all just need to grow up and figure it out the roads are to be shared not owned!
    As for the invention I would be interested to try it out just to see if perhaps there are any real saftey ramifications, and hell if there arent I may buy one for each of my kids so their bikes will leave pretty stripes all the way down the driveway.

  45. Lia says:

    I think this is such a cute idea. Kids would love it. I can think back when I used to go on bike rides with my friends. I know we would have loved to have something like this!

  46. mick says:

    Can anyone tell me the make of the orange bike or were i could buy 1?

  47. Richie says:

    Then pay Road Tax like all other road users. Plus when one of these cyclists makes me swerve in the road because they can’t ride in a straight line, I’ll be able to follow their chalk mark to their destination and let them know how I feel about them!!!
    Seriously this is pointless.

  48. Ed HIdden says:

    Think this could be made to control from the bar so you could “make morse code like” dots at an intersection?

    I’m thinking of a way to do a “hare and hound” type thing on a bike with making a marking at an intersection with Chalk… but still be able to ride while doing it.

  49. some guy says:

    Spreading colored dust on the roads isn’t a good idea. If this were to somehow become the new hipster activism thing to do, it would leave a dust (which is toxic to breath)all over the city. Chalk is made from talc, which is very bad for the lungs. In times of drought, this dust would go airborne, and contribute to the air pollution. Washing it off in the rain means washing it into our streams. what sort of things are they using to color the dust? do we want that in our waterways? This seems short-sighted and selfish by nature.

    Could they make some special tires that leave a streak of clean road behind? that might illustrate the point better. How large does a particle need to be before it is technically considered littering?

    Activism is rarely benevolent, more often, it is a mild act of aggression.

  50. j says:

    This picture is photoshopped, I would know, I’ve seen a lot of shops in my day. The pixellation and jagged color borders in the top picture are definite indications.

  51. jas says:

    hahaha it would mean my mum would be able to tell if my bf had snuck to my house on his bike while she was out =P

  52. B says:

    I guess at least one of the cyclists in the picture hopes that the chalk helps drivers see them, since she wears her bike helmet on her waist. Choosing a chalk trail over a helmet… bad choice.
    It would be cool for kids in the local school parking lot after hours.

  53. Ricardo Rocha Rocha says:

    I´m brazlian and I have conditions to put this product in my country so send all informations about  that

           thanks Ricardo Rocha Rocha.

  54. ron says:

    So much for leave no trace motto.

  55. Bike Accessory Leaves Trail Of Chalk Behind You says:

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Becky Stern is a Content Creator at Autodesk/Instructables, and part time faculty at New York’s School of Visual Arts Products of Design grad program. Making and sharing are her two biggest passions, and she's created hundreds of free online DIY tutorials and videos, mostly about technology and its intersection with crafts. Find her @bekathwia on YouTube/Twitter/Instagram.

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