This is what CB Radios are, and many more people used to have them before cell phones.

People in mountainous areas where a cell phone is useless still do.

As a thought experiment, I’m prepared to momentarily set aside the practical and societal issues to see whether a mechanism for motorists to communicate to any other nearby motorists would have a use.

To set some ground rules, I think it’s fair to assert that such a communication mechanism is not meant for lollygagging, but would be used for some sort of operational reason that is related to driving a motor vehicle. So the use-cases would be broader than just safety or traffic management, and could include coordination between drivers all heading to the same place. This criteria means we won’t require the generality of a mobile phone network (which can call anyone) and instead is very local.

Some examples that might use this mechanism:

1. Broadcasting a safety hazard to motorists further behind, such as objects in the road or right after a sharp curve
2. Telling a specific car that their trailer has lost a strap, that it is flailing in the wind, and it might get caught under the rear wheels
3. Informing all cars in the camping group platoon that you’ll be stopping at Micky-D’s for a bathroom break, and they should keep going
4. For two cars that already drove over some sharp road debris, they can look at each other’s cars to relay any observable damage, to decide whether to stop on the shoulderless highway or keep driving to an exit

This selection of examples represent exigent circumstances that arise while driving, rather than something which could have been planned/coordinated in advance. More over, they cover scenarios that are one-to-many or one-to-one, as well as unilateral messages or bilateral conversations.

We need to also consider what existing cues already exist between motorists, some of which are quite dated:

• Honking (so that someone else will do something that fixes the situation)
• Waving through (to indicate that you are yielding and they can proceed)
• Turning an invisible crank (asking them to roll down their window, despite manual windows being very uncommon now in the USA)
• High-beam flashing (to request they change lanes so that you can pass them; or at an intersection, that you’re yielding and they can proceed)
• Stopping and opening the hood (the time-tested signal that your car has malfunctioned and you need assistance)
• Turning on hazard lights (you have unexpectedly stopped somewhere and cannot move; or you are traveling very slowly; or otherwise, some unspecified hazard exists and you need space to manoeuvre and everyone should be on-alert)
• Left/right indicators (you are going to turn or change lanes; if a parking space, you are claiming that parking space)

Before we even check if these existing cues can be used for the examples above, we can see there are already a fair amount of them. The problem with cues, though, is that they might not be universally understood (eg a motorist from flat Nebraska might not understand the hazard lights on a slow-going truck climbing up Tejon Pass heading in/out of Los Angeles). Moreso, some cues are downright dangerous in certain circumstances, such as waving a motorist into an intersection but neither could see the oncoming fire truck that strikes them.

Notice that for all these cues, only fairly simply messages can be conveyed, and for anything more complicated, it is necessary to “turn the invisible crank”, meaning that you and them need to roll down your windows and talk directly about what the complex situation is. So if a situation is simple, then it’s likely one of the existing cues will work. But if not, then maybe our new car-to-car system might turn out to be useful. Let’s find out.

Scenario 1 is partially addressed by one very long honk or using hazard lights, depending on if the hazard is avoidable or if the hazard requires all traffic to halt. If it is about a small object in the road, then perhaps no message is needed at all, since we assume all motorists are paying attention to the road. If the hazard is a hidden one – such as behind a curve or it’s black-ice – then only hazard lights would help, but it might not be clear to following motorists what the issue is. They would only know to remain alert.

A broadcast system could be effective, but only to a point: motorists cannot spend more than a sentence or maybe even a few words to understand some situation that may only be seconds away. We know this from how roadway signs are written: terse and unambiguous. So if a broadcast system did exist for hazards, then it must be something which can be described in fewer than maybe 5 words. This means the system isn’t useful for info about which parking lots at LAX have room, for example.

Scenario 2 involves a hazard that is moving, and can be addressed by honking and high-beams to get the motorist’s attention. There is no ability to convey the precise nature of the hazard, but outside of nighttime environments where people may be hesitant to stop just because someone is trying to tell them something on a rural Interstate, this generally is enough to prevent a roadway calamity.

But supposing we did want to use our new system to send that motorist a message, the same concern from earlier must be respected: it is improper to flood a motorist with too much info when the driving task doesn’t really allow for much time to do anything else. An apt comparison would be to air transport pilots, where a jetliner at cruising altitude actually does have a lot of spare time, but not when preparing for takeoff or landing. Driving an automobile is a continual task, and for the time when a car is stopped at a traffic light, then there is virtually no need for a car-to-car communication system; just yell. The need for ACARS for automobiles [pun intended] is looking less useful, so far.

Scenario 3 is similar to Scenario 2, but is a one-to-many message. But given how such exchanges tend to also become multilateral (“can you get me a Big Mac as well?” and “well, we don’t have to be at the camp site until 4:20”), this once again starts to become a distraction from the driving task.

Scenario 4 is probably the most unique, because it rarely happens: motorists always have the option of stopping, although stopping can itself create a hazard if the location is not great (eg left lane on an American freeway). It would be truly unusual for two cars to have struck something AND then need to quickly decide if they can press on toward the nearest exit (eg minor body damage) or if they must stop immediately (eg a fuel rupture that starts a small fire beneath the vehicle) AND there is someone else who can mutually exchange info about the damage.

It’s such a contrived scenario, because I actually made it up, based on the similar situation that occurs for aircraft that suffer damage while in the air. In such situations, the pilot would need external support, which can come from a nearby aircraft, or ATC, or an escort fighter jet. For example, if an aircraft cannot confirm safe extension of the landing gear, diagnosing the problem is helped by a nearby news helicopter confirming that the landing gear is clearly visible and locked.

Alternatively, if a departing aircraft has struck a piece of metal dropped by an earlier Continental Airlines DC-10, and that bit of metal causes the left tire to explode, further causing a fuel rupture from the left tank and an uncontrollable fire slowly destroying the wing, it would be very useful if ATC can tell the pilots ASAP before the aircraft is going too fast to abort the takeoff, resulting in an inability to fly and an eventual crash into a hotel.

I bring up my contrived automobile Scenario 4 because it shows how things could always be slightly different if a small factor was simply changed, if maybe there were better warnings to the pilots from their aircraft, or if the Continental plane was better maintained, or if Charles de Gaulle ATC was just a little bit faster to radio to the pilots. So it’s perfectly natural to think that by having this one aspect of the driving experience changed, maybe there’s a lot of value we could get from it. Indeed, the Swiss Cheese Model of accident causation tells us that any one layer could have been different and thus stop the holes from lining up.

But from this thought experiment, we can see that the existing cues between motorists already serve the most common reasons for needing to communicate while on the road. And anything more complicated messages than “I would like to pass” become a distraction and thus less useful and more dangerous in practice. Aviation knows full-well the dangers of introducing a fix which ends up causing more problems in the long-run.

They do. Some people poat their radio frequency their car.

You could publish you phone number right on your car. See how it goes.

Road rage.

That sounds awful. But it does exist, its called a cb radio

Bruh that’s just multiplayer game voice chat IRL. Imagine chaos and trolling.

Honking IS how you contact nearby vehicles.

It’s not a bad idea, but there are plenty of countries where it would be abused to xbox live chat levels.

Yeah no people are trash on average, I don’t want to get constantly pinged by trashy people while driving, I don’t even like proximity chat in games, imagine having that in real life, there’s a high chance of accidents happening due to distraction. Now if someone wants to add a little display on their car that can display some basic text messages, maybe that could be of some use

I used to have a cat that loved to jump up under any truck that would be delivering something. We used to tell them not to leave until we had eyes on our car. Even with that, he was such a varmint that I’d give them my business card, and tell them that if they got to their next delivery, and found him in their truck, to call me, and I’ll come get him.

Luckily, our precautions worked, but he was a troublemaker.

This might shock you but I dont want nearby people to be able to talk to me. Chicken or not.

Lady honked at me the other day for not turning left at a light (she obviously didn’t see the motorcyclists) and began making rude gestures.

Well anyway it’s probably better that we can’t talk to each other.

CB radio? That shit is for truckers and nerds but it was solid.

We do…?

It’s called a CB radio. Though usually it’s only semi-trucks and enthusiasts that use 'em. It would be pretty awesome if they were just a standard feature, tho.

Dude, people can’t handle the complexity of simply driving the vehicle as it is. Bad things happen when adding handling dynamic communications into the mix with people who aren’t trained to the level of combat pilots. That’s why we don’t let people juggle a cell phone while driving.