Why AI Autonomous Cars Aren’t Yet Paying Attention To Honking Horns   

For developers of AI driving systems for self-driving cars, the ability to detect and process the sound of a car horn is an edge case right now. (Photo by Milivoj Kuhar on Unsplash) 

By Lance Eliot, the AI Trends Insider 

Horn honking. We’ve all done it; some more so than others. It used to be that honking a car horn was quite customary and an expected element in the act of driving. 

Indeed, when I first learned to drive, the driver training class included a brief segment devoted to the use of the car horn. For example, we began by employing the horn in a delicate fashion, such as lightly tapping the horn to generate some casual and modestly alerting toots. We also were later taught to lean on the horn and generate an ear-shattering blast, just in case an outstretched use of the car horn was warranted.   

All told, the notion was that you needed to know how to use your car horn for a wide variety of circumstances. The horn was integral to driving a car. Akin to knowing how to steer, speed up, slow down, and the rest, you likewise should be versed in the use of the car horn. The logic was quite direct, if cars are equipped with car horns, there is assuredly a reason for having them, and any newbie driver should be proficient in using such equipment.   

You might go so far as claiming that the use of a car horn was fine art, if you will. The person using a horn was considered responsible for doing so. They had to sparingly use a horn. This was not a trifling feature on a car. It was a potentially lifesaving device.   

The situations that warranted the use of a car horn were supposed to be relatively serious and not for simply playing around. If another car was dangerously veering into traffic, and it seemed that the driver was not aware of what they were doing, a hefty dose of the horn was considered appropriate. Better to alert the driver and perhaps overstate the case via the sharpness of the horn versus allowing a bad predicament to turn into an injurious car crash. 

Besides the occasions when a horn was used to aid and protect yourself, other cars and even pedestrians, there was leniency to sometimes use the horn for fun. You might be driving along and see your best friend walking on the sidewalk, so you would do a light tap of the horn to get their attention. The friend would smile and wave at you. You would wave back. All in all, an innocent and everyday occurrence. 

Of course, like most things, car horns eventually became used in rather abrasive ways. As they say, that’s what sometimes happens with nifty toys. They get extended into untoward uses that go far beyond what was initially expected.   

One of the most common uses of a horn that is decidedly over-the-top consists of honking a horn at the very instant that a traffic signal goes from red to green, doing so when a car is sitting directly ahead of you and that hasn’t gotten underway just yet. It is one thing to wait a solid handful of seconds and then consider doing a courteous short burst as a reminder that the light is green, while it is something entirely different to use the horn like a massive claxon and browbeat the other driver by stunning them with a bone-breaking blast of sound at the instant a light goes green.   

That’s not cool.   

The thing is, a person using their horn in this aggressive manner is seemingly saying that the other driver is a complete dolt. Wake up, you idiot! Get your car in gear and get the heck going! That’s what it conveys to the person that might have been ready to get underway and merely needed a moment to start doing so. They might consciously be waiting momentarily for the intersection to clear or have some other bona fide safety basis for slowly proceeding ahead.   

Meanwhile, the horn blasting person is boiling mad that the driver has not pushed the pedal to the metal. Maybe this feverish horn blaster is late for work or has been caught behind slowpoke drivers throughout the entire day. For whatever reason, the person armed with a horn decides that it is the best way to motivate others around them. 

Regrettably, this way of thinking often means that they use their horn repeatedly, almost constantly, for any perceived “infraction” by other drivers or pedestrians.   

Of course, the response to getting bleated with a harsh horn blast is not necessarily going to be what the horn user expected.   

Some drivers that get an anxious horn smacking are apt to go into a form of road rage. They might decide to purposely not proceed at all, staying still, doing so to further frustrate the person that has used a horn. Take that, is the thinking of the horn respondent. In turn, the horn user will likely try using the horn again, perhaps more so than the first blast.   

The whole matter cascades out of control. 

Another possibility is that the horn blast causes the driver to look around in anticipation of seeing something that causes them purposely to remain still. In other words, their interpretation of the horn blast was that the driver behind them was helpfully warning them about a danger brewing. Perhaps this horn user saw that a pedestrian had wandered into the street and was trying to make sure that the car getting honked does not mow down the innocent person on foot.   

You might roll your eyes on that one.   

The odds that someone would use their horn as a means to aid others and not due to a semblance of greed would seem like a stretch in today’s world. To be clear, I’m not saying that it never happens, only that the chances of that occurring are relatively slim. A hornblower is usually telling others to pretty much get the heck out of their way, rather than seeking to keep the peace and altruistically aiding others. I realize that seems a bit pessimistic, sorry to say.   

That’s part of the whole problem with using a horn. Like a box of chocolates, you never know what you are going to get (well, more directly, you don’t know why the car horn was utilized).   

The insurmountable problem is that a horn blast has no particular meaning associated with it. The horn does not tell what the horn has been used for. Nobody knows, other than the horn blaster. What might be in their minds is at times an utter mystery. There could be a good reason for the horn being used, or there could be a wild and completely nutty reason for using the horn.   

In addition, you don’t know who the horn is being aimed at. Is it the car immediately in front of the horn honker? Is it somebody standing on the sidewalk? Is it a vehicle barely visible and already down at the end of the block?   

Consider what reactions can occur to the use of this non-specific form of communication. 

I’ve seen some drivers that were blasted with a horn that decided to allow the horn blasting car to proceed ahead of them. The driver then sneakily positions themselves directly behind that car. Once they are in the needed position, they start honking their horn at the other driver. Incessantly. The idea is that, presumably, it makes sense to give that horn user a taste of their own medicine. 

It could be that the original blast of the horn had nothing to do with them. Unfortunately, given that the horn is a scatter-style communiqué, everybody within earshot might think the horn was intended for them. 

The resulting road rage incidents can turn deadly and drag an entire slew of participants into the melee. None of them necessarily know why the horn was used. None of them necessarily know who the intended target was. All they know is that somebody used their car horn and it was irksome that they did so.   

People go to fisticuffs or worse sometimes. 

All because of the use of a car horn. 

In California, the DMV (Department of Motor Vehicles) has this official Vehicle Code verbiage about car horns (see Section 27001): “The driver of a motor vehicle when reasonably necessary to insure safe operation shall give audible warning with his horn,” and furthermore “The horn shall not otherwise be used, except as a theft alarm system.”   

The formal rules emphasize that a car horn is only to be used when reasonably necessary, and otherwise isn’t supposed to be used.   

There is a bit of a loophole in that the interpretation of what is reasonable versus unreasonable is open-ended. Thus, a malcontent might in their noggin believe that using their car horn was reasonably necessary, even though to any independent third party the usage was egregious and utterly unnecessary in the circumstances. This is something that judges and courts often have to decide when such horn squawking cases arrive at the courthouse.   

Within the California DMV Driver’s Handbook, the recommendations are that you should only use the horn when necessary, doing so to avoid collisions. You can also use the horn to get eye contact with other drivers, though presumably once again as a means to avert a collision. And there are allowed special cases such as using a horn on a narrow mountain road (providing a verbal alert for cars that are also using the road but might be hidden from view).   

For those of you that have ever visited New York City, you might remember that the jarring sounds of car horns used to be a well-known part-and-parcel element of being in the city that never sleeps. During the day, you would hear the constant din of honking horns. On top of that, all night long there would be the blaring sounds of car horns too. Cabbies used them extensively. Everyday drivers used them. Truck drivers used their horns. It was an orchestra of grand proportions, though playing essentially one note, over and over again. 

The joke used to be that assuredly this must be the city that never sleeps, due to the fact that the yapping horns kept you up all night. You had no choice but to remain awake. Anyone trying to sleep in their hotel room or apartment had to cope with the never-ending sounds of those ubiquitous and sleep-wakening horns. 

Eventually, enough was enough, and the authorities decided to try and curtail the incessant horn honking. Official traffic signs were posted that warned drivers to be aware that no honking was allowed in the realm of the posted sign. Laws were passed that stated the use of a horn was only allowed for emergency circumstances. A hefty fine was assigned to any tickets that involved the unnecessary use of a horn. Etc. 

Some would say that discouraging the use of car horns is fundamentally wrong.   

If that catches your attention, allow me a moment to explain.   

They would argue that horns can be a vital tool for driving. Imagine all the lives saved or injuries averted by having used a horn as a keystone to achieving safety. If you suppress the desirability of using a car horn, you are going to lose out by making drivers second guess the use of the horn. In turn, when situations arise that somebody would have been saved by the chance of a horn bleating, the driver probably won’t use their horn and the otherwise in-danger person will suffer whatever calamity was awaiting them.   

It is akin to the old expression about tossing the baby out with the bathwater (a piece of wisdom that by today’s standards is a bit rusty). The point being overall that the horn can be used for good, and by making the use of a horn into a bad thing, you are swinging too far and going to fall prey to situations that a horn use would have been crucial.   

That’s one position or perspective about the intrinsic value of using a car horn.   

Here’s another one that might raise your eyebrows. Some have argued that honking your car horn is a First Amendment right. 

You see, a horn could be construed as a form of expression. Perhaps you opt to honk your horn in protest of some matter that concerns you. The car horn is not being used at that moment for traffic or driving purposes. Instead, it is the use of sound as an expression of your angst or declarative statement that you are trying to convey.   

Generally, the courts have not especially given the green light to such a legal posture. You’ve probably heard about the famous notion that your freedom of expression does not necessarily allow you to yell “Fire!” in a crowded theater. To some degree, the use of a horn when in traffic has a similar connotation. This is a complicated legal aspect and something still being bandied about in the courts.   

Whew, that’s a lot about car horns.   

Based on this overall discussion, I would guess that you’ve likely come to the conclusion that car horns have many useful and yet also nebulous facets. 

The horn itself is not especially the issue. It is those that choose to use the horn. Sure, we could remove all horns from all vehicles, dispensing with the topic entirely, but this would undeniably excise the chances of using a horn for the revered reasonable and contributory purpose it is intended.   

It is relatively safe to say that car horns will remain a standard feature of cars.   

Meanwhile, consider that the future of cars consists of AI-based true self-driving cars. 

There isn’t a human driver involved in a true self-driving car. Keep in mind that true self-driving cars are driven via an AI driving system. There isn’t a need for a human driver at the wheel, and nor is there a provision for a human to drive the vehicle.   

Here’s an intriguing question that is worth pondering: What will happen if you opt to use your horn toward an AI-based true self-driving car that might be nearby you while underway via your conventional human-driven car?   

Before jumping into the details, I’d like to further clarify what is meant when I refer to true self-driving cars.   





Understanding The Levels Of Self-Driving Cars 

As a clarification, true self-driving cars are ones where the AI drives the car entirely on its own and there isn’t any human assistance during the driving task. 

These driverless vehicles are considered Level 4 and Level 5, while a car that requires a human driver to co-share the driving effort is usually considered at Level 2 or Level 3. The cars that co-share the driving task are described as being semi-autonomous, and typically contain a variety of automated add-on’s that are referred to as ADAS (Advanced Driver-Assistance Systems).   



Since semi-autonomous cars require a human driver, the adoption of those types of cars won’t be markedly different from driving conventional vehicles, so there’s not much new per se to cover about them on this topic (though, as you’ll see in a moment, the points next made are generally applicable). 

For semi-autonomous cars, it is important that the public needs to be forewarned about a disturbing aspect that’s been arising lately, namely that despite those human drivers that keep posting videos of themselves falling asleep at the wheel of a Level 2 or Level 3 car, we all need to avoid being misled into believing that the driver can take away their attention from the driving task while driving a semi-autonomous car.   






Self-Driving Cars And Some Honking Going On   

For Level 4 and Level 5 true self-driving vehicles, there won’t be a human driver involved in the driving task. All occupants will be passengers; the AI is doing the driving.   

One aspect to immediately discuss entails the fact that the AI involved in today’s AI driving systems is not sentient. In other words, the AI is altogether a collective of computer-based programming and algorithms, and most assuredly not able to reason in the same manner that humans can.   

Why this added emphasis about the AI not being sentient?   

Because I want to underscore that when discussing the role of the AI driving system, I am not ascribing human qualities to the AI. Please be aware that there is an ongoing and dangerous tendency these days to anthropomorphize AI. In essence, people are assigning human-like sentience to today’s AI, despite the undeniable and inarguable fact that no such AI exists as yet. 

With that clarification, you can envision that the AI driving system won’t natively somehow “know” about the facets of driving. Driving and all that it entails will need to be programmed as part of the hardware and software of the self-driving car.   

Let’s dive into the myriad of aspects that come to play on this topic.   

The question to be pondered here is what will happen if you honk a horn at an AI self-driving car.   

Turns out, I am around self-driving cars quite a bit and witness people that do indeed honk their horn at a self-driving car. But before I delve into those details, we can consider a somewhat allied question.   

If a tree falls in a forest, will it make a sound? 

You’ve certainly heard that question before. Seems like an age-old conundrum.   

The answer to that question is relatively straightforward, plus it provides insights into what will happen when someone honks at a self-driving car. Those two topics seem to be completely disconnected, but you’ll see in a moment that they are similar in key respects. 

When a tree falls in a forest, there will undoubtedly be vibrations or waves that carry through the air. Anyone or presumably anything that can sense the vibrations and has apparatus known generally as the act of hearing will ostensibly hear the crashing sounds. If you define the word “sound” as referring solely to the vibrations and ergo omit the need for a hearing mechanism, you could claim that the fallen tree did make a sound, regardless of whether anyone or anything was nearby to hear it.   

Meanwhile, if you insist that “sound” must encompass a hearing mechanism, and suppose there aren’t any hearing mechanisms within earshot, you could contend that the falling tree did not make a sound. In that case, when there aren’t for example any people or animals around that have the sense of hearing, it is feasible to argue that there wasn’t any sound associated with the crashing tree.   

Hope that straightens things out.   

This is directly related to a self-driving car via the notion of whether a self-driving car has any provision for detecting sounds that emanate from outside the autonomous vehicle. Some self-driving cars are not yet equipped with externally facing microphones. Thus, the self-driving car is unable to detect sounds coming from the streets such as the engine noises of other cars, the chatter of nearby pedestrians, and nor the sound of a honking horn.

Without some sensory device intended for detecting sounds, the AI driving system is not going to have any tangible input that a horn is being honked by someone. Note that there might be microphones within the interior of the self-driving car, often established to allow for interaction with passengers, though these microphones would only tangentially pick up external sounds, if at all.   

In short, for the case of self-driving cars that are not set up with externally-oriented microphones, the honking of a horn at a self-driving car is futile and will not be detected. I suppose you might conceive of this as akin to having a human driver at the wheel that is unable to hear anything that originates outside of the vehicle, perhaps because of their lack of hearing or due to the vehicle being so airtight that no sounds can penetrate the interior.   

One concern about self-driving cars not being equipped with external-facing microphones entails the lack of being able to detect that an emergency vehicle might be nearby. Human drivers are expected to listen for ambulances, fire trucks, police cars, and other emergency vehicles that use their sirens to forewarn other drivers of their presence. An AI driving system would not viably be able to do this type of detection without an audio input capacity, other than scanning visually via the video cameras or using radar, LIDAR, etc.   

Another qualm is that AI driving systems are potentially unable to detect any spoken commands or shouting that might occur by people around or near a self-driving car. A pedestrian might seek to yell loudly at a self-driving car to watch out for a child up ahead, yet the AI driving system might not detect such a warning due to a lack of outward-mounted microphones.   

In the case of self-driving cars that have a human serving as a backup safety driver, there is a chance that this human might hear a honking horn (and other external sounds too, naturally). You see, many of the existing self-driving car tryouts on our public roadways have a person employed and sitting at the steering wheel as a monitor of the AI driving system. The human is supposed to disengage the AI and take over the driving controls when needed. 

We, therefore, have two variations about the hearing of a honking horn. One is that the self-driving car won’t detect the horn since there aren’t any audio devices provided for that use. The other is that a human backup driver might be in the vehicle and potentially hear the honking horn, for which the driver might then take over the driving. 

Those are the most likely aspects currently.   

The third variant is a self-driving car that is equipped with externally facing microphones. This suggests that the AI driving system will possibly detect the honking horn. The key will be whether the AI developers have programmed the AI driving system to take as input the audio detections, along with having some form of pattern detection to ascertain that the sound is in fact a honking horn (there obviously can be a lot of street-related sounds detected during a driving journey). 

Imagine that you are an AI developer and you need to program the AI driving system to contend with what appears to be the sound of a honking horn. What would you have the AI driving system do upon its detection of a horn sound?   

That’s a tough one.   

Recall that we’ve already covered the vacuous nature of a honking horn. A human that is honking a horn might be doing so for innumerable reasons. Furthermore, the horn honking might have nothing whatsoever to do with the self-driving car. A person might be honking at other cars, or pedestrians, or at a duck that was waddling next to a pond that is adjacent to the roadway.   

Human drivers oftentimes have no semblance of why someone honked their horn. Figuring out whether there was a bona fide roadway safety concern requires looking around extensively and trying to ferret out what might be the basis for the honked horn. This analysis of the driving scene might turn up empty as a revealing indicator for the horn being used.   






There are a lot more twists and turns on this seemingly simple topic.   

Via observation, I’ve ascertained that some human drivers honk their horns at self-driving cars because they are trying to declare that hey, this is neat, it’s a self-driving car. This is akin to seeing something unusual on the roadway and honking just to point out the extraordinary appearance of the object or thing. Of course, this is generally an improper and illegal use of a car horn, assuming that the circumstance does not involve the pending possibility of a collision or equivalent.   

In addition, some smarmy human drivers believe they are being clever by honking at a self-driving car, as though this is a means of testing the capabilities of the AI driving system. Please don’t do this. Once again, it would usually be considered an illegal use of a car horn.   

Then there are the sincere cases. A human driver might genuinely be using their car horn upon noticing that the self-driving car appears to be heading toward a collision. The hope presumably is that the AI driving system will detect the sound and take evasive action, or that a human backup driver is present and will take over the driving controls.   

Lamentably, dealing with horn honking is considered an edge or corner case for many of the existing self-driving car development efforts. An edge or corner case is something that is not considered at the core of the task at hand. The item is placed onto a list of lower priority considerations and will someday get attention (some also assert it will be negated entirely and replaced by electronic transmissions such as V2V and V2P).   

As mentioned, honking your car horn is like a box of chocolates. Besides not knowing what you will get, there is also the consideration of whether any falling trees in the forest will be heard. 

That’s for darned honking sure. 


Copyright 2021 Dr. Lance Eliot