Disabling Self-Driving Cars with a Traffic Cone

You can disable a self-driving car by putting a traffic cone on its hood:

The group got the idea for the conings by chance. The person claims a few of them walking together one night saw a cone on the hood of an AV, which appeared disabled. They weren’t sure at the time which came first; perhaps someone had placed the cone on the AV’s hood to signify it was disabled rather than the other way around. But, it gave them an idea, and when they tested it, they found that a cone on a hood renders the vehicles little more than a multi-ton hunk of useless metal. The group suspects the cone partially blocks the LIDAR detectors on the roof of the car, in much the same way that a human driver wouldn’t be able to safely drive with a cone on the hood. But there is no human inside to get out and simply remove the cone, so the car is stuck.

Delightfully low-tech.

Posted on July 18, 2023 at 7:13 AM24 Comments


Winter July 18, 2023 8:28 AM

Spraying paint on the windshield makes a human driven car equally disabled. The one difference is that the human will get the paint removed, but the self-driving car cannot do so.

Clive Robinson July 18, 2023 8:35 AM

@ Bruce,

“Delightfully low-tech.”

But maybe not as modern as you might think…

In the UK we had,

“Cones on the hoodie”

Back in the days of Harry Potter films…

Inebreated youth that should not have had access to such chemicals used to put traffic cones on their head and lampoon/ape about as the “boy wizzard”.

Whilst not compleatly immobilized by the cone, their abilities to navigate were extreamly reduced to put it politely. And when “The boys in blue” turned up immobilization by stainless steel not so fashionable wrist accessories and bouncing of the back doors of white vans was not unknown…

I was way to old for it to be part of my “mis-spent youth” but there are a few people around who have been awarded ASBOS not golden globes for their efforts. As “lifetime achivment awards” ASBOS have little to recommend them…

[1] The short lived ASBOS, did not in England and Wales live long enough to reach the “Age of Consent” or Majority…


Clive Robinson July 18, 2023 9:17 AM

@ Winter, ALL,

“Spraying paint on the windshield”

Is vandalism and therefore subject to criminal sanction…

However in the UK putting a “Post-it” note on a windscreen has been decided in court as not vandalism.

But the use of other sticky tapes or glues that leave residue so prsent a potential hazard to driving are vandalism.

So rather than “Cone Week” they maybe should have “Post it Month” with a note saying “Please Do not park here”.

@ Bruce, ALL,

It’s been said that some years ago now, the French started “clamping cars” to raise revenue amongst other things. But as a scheme it failed miserably, because an enterprising group that very quickly grew squirted Super-Glue into the clamp locks making them incredibly difficult, costly and time consuming to remove. Thus the effect was to make the traffic problem worse a lot worse, so things in typical French Fasion “Returned to the old ways”

In the UK we’ve had,




Which are all vandalism if not worse.

Ted July 18, 2023 9:47 AM

Spare a cone, attend a meeting!

Is it true tho? According to a CPUC workshop slide deck, Cruise AVs were involved in 92% fewer collisions as the primary contributor (in their first million driverless miles).

K.S. July 18, 2023 11:14 AM

I listened to Lex Fridman podcast, I think with George Hotz, where AI for self-driving was discussed. One interesting idea was that training criteria should be whether human chose to disengage the autopilot. Following that criteria, I think traffic cone on the hood meets ‘disengage’. The alternative, that we have an autonomous cars dragging large debris such as large branches or downed wires and causing damage to the surroundings and itself.

K.S. July 18, 2023 11:22 AM

@Clive Robinson

A more interesting attack would be a “Post-it” note with an image that directly undermines image processing, such as fooling the car to think speed limit is ultra-low, resulting in obnoxiously slow driving in the traffic.

The resulting court case would have to decide whether knowingly misleading the autonomous robots to cause undesirable or potentially damaging behaviour transfers the responsibility for that behaviour onto the party that did misleading. Essentially, is free speech applicable to interaction with robots that cannot be not reasonably expected to be able to assess veracity of such speech.

Steve July 18, 2023 12:03 PM

In California, AV manufacturers must “report any collision that resulted in property damage, bodily injury, or death” to the Department of Motor Vehicles. These reports are publicly available:


I did a “back of the envelope” study a couple of years ago by scraping those records (a bit of a pain, since they’re in PDF form) and found that a substantial majority of the accidents, most of which were minor “fender benders,” happened either while the vehicle was in “manual mode,” that is under the control of the human driver, or were most likely the fault of another driver.

A lot of them were “rear enders” while the AV was properly stopped at a light or a stop sign.

Make of that what you will.

iAPX July 18, 2023 2:52 PM

@Mexaly, All

I confirm, and it’s not only autonomous vehicles that are blockables, but also any vehicle with a break “assistance” to avoid collision with pedestrian.
By “assistance” I mean the driver didn’t have any control on the brake or the ability to not stop.

This is an interesting scenario for when these “assistances” will be ubiquitous…

Speed July 18, 2023 4:50 PM

Why is this news? If a foreign object appears on the hood of an automobile the options are two: Stop the car or keep going.

Without any additional information, stopping the car is the best option.

I suppose others might believe that the car’s various systems should be able to decide exactly what is on the car’s hood and make a decision about how to respond. And those people might assume that an autonomous vehicle should have an encyclopedic knowledge of all things that might appear on the hood and enough human-level smarts to correctly decide what to do about it.

Or maybe the default should be, “Drive On!”

JonKnowsNothing July 18, 2023 6:08 PM

@Speed, All

re: Stop v Drive On

Urbanites rarely consider farming or heavy mechanical equipment when reviewing Auto-Driving Systems. Farmers have had them for centuries. First there were oxen and horses which learned where they needed to go plow, when to make the turn around, when to start and when to head home. Later motorized tractors became the norm.

Farm equipment is set “in motion” and the tractor goes in the direction pointed until otherwise halted. There’s a Dead Man’s Switch to stop the tractor, and most farmers disable it. A tractor hauling irrigation pipe on a trailer generally has to go a long way to get to the end of the field. The farmer and crew walk beside the trailer and lift out the pipe sections, connecting them up to the previous section and walk forward to the next join.

This is not a high speed operation and when the farmer gets to the end of the field, they hop up into the cab and make the turn.

The thing is, if the farmer fails to stop the tractor, there goes the fence line and the cattle in the next field all take advantage of The Get Away Break.

Of course, the other significant problem happens all too regularly, the farmer is run over by his own equipment with fatal outcomes. It’s dangerous to be a farmer.

So, it’s not an unknown problem and solutions vary depending on circumstances.

One interesting condition is travel though a “safari or safari park”. Generically, a motorized vehicle travels along a designated pathway to view animals in a large open fields where the people are confined to their cars.

Many stories abound of how a lion decides the nice warm hood of a car is a great place to take a nap. In one of the Big Cat Diaries a large cat clambered on top of the jeep’s canvas sling roof and gave a watering to the occupants.

Perhaps a plush lion would be just as effective and much more fun?


ht tps://en.wikipedia.o r g/wiki/Stuffed_toy

ht tps://en.wikipedia.o r g/wiki/Big_Cat_Diary

(url fractured)

Brad Templeton July 18, 2023 6:20 PM

No big surprise with a technology that is designed to, in its initial years, be ultra cautious and to stop and disable it self if anything is wrong. In fact, people are complaining about how readily they do the “minimal risk” action and just stop in the street.

So hardly a security flaw. Not even a bug at present but a feature. Though in time they will get more tolerant of strange things.

JonKnowsNothing July 18, 2023 11:12 PM


One of the foundation problems is the desire that self driving vehicles should have no restrictions on directional movement.

We have had rail transports of many types, trains, buses, street cars, cable cars, monorail trains etc. that have fewer problems to deal with because their route is fixed.

It’s when the route is open ended and uncontrolled that things get very dicey.

Fixed rail systems do have “the trolley car” problem but to a much lesser degree than open route systems where they cannot tell a bicycle from a basketball; where a discoloration on a sign or lens reflection can cause uncontrolled collisions.

iirc(badly) circa 1900-1960 Los Angeles had very good fixed rail and overhead wire bus and tram systems. They worked extremely well and for those times, low cost. A deal was struck with petroleum corporations, car manufacturers and tire makers to rip up the street car system and replace it with dismantled mountains to create the freeways in order to increase sales for all involved.

We still believe in the Jetson’s fairy tale.


ht tps://en.wikipedia.o r g/wiki/Angels_Flight

  • modern does not mean improved

(url factured)

Clive Robinson July 19, 2023 2:56 AM

@ Brad Templeton, ALL,

“So hardly a security flaw. Not even a bug at present but a feature.”

No it’s actually an insoluable problem as the vehicle lacks “authorative agency” unlike a human owner/driver to resolve it.

Therefore it’s a fundemental system flaw that can be exploited easily to the detriment of the system it’s owner and importantly the environment it’s in.

So yes that makes it a real world physical security problem from that point on.

As regards,

“Though in time they will get more tolerant of strange things.”

No, the system as is lacks not just “agency” but importantly unlike a human driver “authorative agency”. So it can not just get out of the vehicle clear the hood and know it can drive away safely.

If as the logical conclusion of your comment, the vehical autonomously drove away with the cone on the hood then by definition it would be “Driving Dangerously” as would any human driver going down the road with a vision blocking and attention distracting traffic cone on the hood, that could come off at any moment and cause a harm (you know those laws about “insecure loads”).

You have to remember the law works by the least surprise to “all involved”, which includes other drivers and road users “in the environment”. It’s why pretending to jump out in front of a car or similar or even use a horn etc to distract another driver is considered unlawful behaviour or a crime (think of it as an extension of the “shouting fire in a crowded auditorium is not ‘Free Speach'” principle).

Be it a road cone or a post-it note it would be unlawfull for the vehicle to be moved as it is “in an unsafe condition”. The autonomous drive vehicle does not have agency to remove the object therefore the only lawfull action it can do is wait for the object to be removed by someone or something with “authorative agency” to do so.

But it goes further… If as an individual who is not the vehicles “registered keeper” or “owner” are you actually qualified or even alowed to remove the cone or post-it?

The answer legaly is “no”, it’s not your vehicle and by doing so you are making an alteration to the vehicle you are not authorised or probably qualified to do. In effect it could be compared to taking the parking break off, or removing a “do not use” safety tag, if the vehicle then moves and causes harm then you would be liable for the harm caused not the vehicle owner.

Robin July 19, 2023 10:10 AM

I suppose AVs have windscreen wipers; how long before they get “hood wipers” to essentially give clear “vision” and remove random detritus ? Or maybe a robot arm which could also be used to load luggage into the back?

Peter A. July 19, 2023 11:12 AM

One of the unintended consequences of AVs may be easier hijacking/carjacking. Block the road using some trivial object like a trash bin, brake check, cut in front etc. Human driver would see the danger and may try to break through an obstacle or get around it by going over lawn, sidewalk etc. AV will most likely stop leaving the passenger vulnerable.

Unless the passenger is an able driver and has an option to disengage the autopilot and take over (and pays attention).

Winter July 19, 2023 11:35 AM


One of the unintended consequences of AVs may be easier hijacking/carjacking.

But the car will call the police, send them the coordinates and pictures of the culprits. The car will probably be remotely blocked and locked.

An AV is a driving networked computer.

iAPX July 19, 2023 5:18 PM

@Winter, All

But the car will call the police, send them the coordinates and pictures of the culprits.

Essentially, if police intervene in the area where you have been hijacked, and that’s not warranted in some places, even around Paris, they will come within few minutes if not few dozen minutes (real-life time) to find harmed people. Then they will call an ambulance, same time approximately.

They will have nice pictures of masks, black hoodies, jeans and sneakers for their own collection.

The problem in some places is to avoid being blocked, I call it defensive driving, by creating space with other vehicles and evaluating options to disengage yourself from an assault, and being able to protect your life even if it means to damage your vehicle, or push someone out of your way!

There are places where all of that is happening. Daily. Near Paris and sometimes inside Paris. I won’t be surprised if it happens too in many areas in other first-world countries.

Winter July 20, 2023 1:34 AM


The problem in some places is to avoid being blocked,

There are many ways people can be kidnapped. Defensive driving is an acquired skill and requires ignoring traffic rules, and the law. All things we most definitely do not want AVs to practice.

An AV can protect against stealing your car and get help. If you are afraid of being kidnapped, you should take precautions that might involve using certain transportation like AV.

But by far most people have more to fear from traffic violations and drunk drivers than kidnappers.

Jon July 20, 2023 1:54 AM

Gotta love the low-tech stuff.

For the Great Train Robbery*, one of the conspirators had figured out how to ‘hack’ railroad signals to make the train stop in the remote area they wanted it to.

Naturally, the rest of the conspirators were delighted to hear it, but less impressed when they saw how: He just clipped on power to the red light (stop), and for the valid green signal (proceed) he just stuffed a glove into the light housing.

There are all manner of other very low-tech ways of defeating very elaborate defenses (see also Randall Munroe’s** $5 wrench).

  • England, 1963. hXXps://www.britannica.com/event/Great-Train-Robbery

** XKCD, hXXps://xkcd.com/538/

mortberg delamon July 22, 2023 10:52 PM

  • We are the Conehoods, we are from France.
  • Oh France, that explains everything.

Charlie August 15, 2023 12:43 PM

>> “Spraying paint on the windshield”

Is vandalism and therefore subject to criminal sanction…

However in the UK putting a “Post-it” note on a windscreen has been decided in court as not vandalism.

Vandalism isn’t a thing in UK law.

You’re thinking of criminal damage.

Surprisingly “damage” isn’t clearly defined in the criminal damage act 1971, see: https://www.cps.gov.uk/legal-guidance/criminal-damage#a04

Clive Robinson August 15, 2023 3:56 PM

@ Charlie,

“Vandalism isn’t a thing in UK law.”

Nor surprisingly to many are a lot of “normal wordage” acts of antisocial activities.

“Surprisingly “damage” isn’t clearly defined…”

Nor is pornography.

They all appear to fall under that “man on the Clapham omnibus” and “you know it when you see it” reasoning.

And we may have reason to be thankfull for the discretion it gives. Because some newer legislation has caused problems.

For instance taking a photo of your kids at the beach can make the photos CSAM and there is no defence against it.

Worse as has been demonstrated that type of law effects people seeking medical help. Due to C19 lockdown “visiting the doctor” got replaced with “sending photos to the doctor”. Reported in the US MSM was a man who was asked by his doctor to send a photo of a rash his son had. The photo was regarded as CSAM by Google and apparently reported to authorities and a warrant issued the entire account seized and shut down. The US police apparently cleared the man,


However in the UK the law apparently gives “no defence” so the out come would have been different…

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