Case in point: The City of Las Vegas and AAA's self-driving shuttle, one of the most advanced public autonomous trials in the U.S., was hit by a semi-truck within hours of its maiden trip last month. The Navya Arma bus was stuck between a car behind it and the slowly advancing truck, which backed its way into the the shuttle. 

The shuttle behaved exactly as it was designed to in the situation, according to a AAA rep — but it didn't move or, more importantly for the truck driver who might not have seen the vehicle behind it, honk a horn to make its presence known. One of the most essential tools for interpersonal communication between drivers wasn't even in the AI's protocol, which made us wonder: Can self-driving cars even beep?

The answer in this particular instance is yes, but the feature is limited to certain situations. "The shuttle does have the capacity to automatically honk its horn, but that function wasn't designed for defensive driving techniques — such as honking when an object is actively backing toward the vehicle," AAA's rep told Mashable in an email. Instead, the shuttle beeps "offensively," when objects in its path like pedestrians or idling vehicles don't move after several seconds.  

The question of whether AVs can honk has wider ramifications than just the trial in Las Vegas. Robocars will share the roads with human drivers for a protracted period of time in the future, since it will probably take decades for human-operated cars to be eliminated from the roads completely. There will be a learning curve for everyone, and mixing people and robots together will require increasing levels of communication between humans and machines to replace the system of beeps, waves, and middle fingers that rule the road today.  

Fostering these systems of communication will be one of the biggest jobs for AV developers, since honking and other audio and visual alerts are essential to the task of driving. Industry leader Waymo has worked to create the proper protocols for its self-driving vehicles to honk their horns, with different types of beeps to signal intention to other drivers on the road. 

Silicon Valley AV startup Drive.ai has also emphasized machine-human interaction in its platform since launching out of stealth mode last year, and it has shared images of concept designs equipped with obvious visual cues for pedestrians and human drivers on the road. The company's most current platform can automatically beep in response to on-road stimuli, for the record — but Drive.ai's CEO Sameep Tandon has wider concerns than just giving the vehicles a horn to honk. 

"We’re really interested in the question of how do vehicles communicate with the outside world and how we can use that to enhance trust," he said in a phone interview. "How do we know that the vehicle is going to be transparent about what its doing? If it does sense danger, it should be able to communicate." 

Signaling intention is a two-way street, however, and Tandon says people need to adjust their expectations to help bring AVs along.

"Generally speaking, [building AV communication] is something where it’s going to be a combination of working with people and society at large so that people understand that hey, these are robots — maybe I should behave slightly different around them," he said. "It’s not the type of thing where there’ll be one solution and it’ll solve every single thing, there’s going to be a need to meet in the middle and work with society to get there."

Emilio Frazzoli, CTO and Chief Scientist for recent Delphi acquisition and fellow Lyft partner nuTonomy agrees that collaboration in communication will be key to a future filled with self-driving cars — but nuTonomy's vehicles don't have protocols to honk their horns at the moment. He said in a phone interview the company is instead focused on perfecting the systems that control blinkers and active signaling, which he believes are used more often than a horn, and therefore more important.  

That's not to say that audio cues are excluded from nuTonomy's platform entirely. "Personally I hate beeping and people who do that," said Frazzoli. "One of the ways we had our cars signal to human driven vehicles nearby that the car is 'annoyed' with their behavior was to actually play the sound of angry R2-D2 from Star Wars. That was kind of cool because it wasn’t perceived as rude, but it made people consider what they might be doing wrong. It worked pretty well."

The main goal of AV technology is to create safer roads, whether the cars can beep or not. Even though the systems aim to make a fundamentally imperfect task perfect by removing the flaws flesh and blood drivers bring to the steering wheel, however, the only way they'll be able to coexist with people on the road will be to embrace the ways humans interact.

That's a fine line to straddle for the teams developing the systems, like the AAA rep who told us that the shuttle scenario happened in part because the AV didn't behave like a human driver. Waymo's engineers approached their beeping training in a similar manner, with an explicit goal to give the platform the same type of capabilities as a "patient, seasoned driver."

The key for successful self-driving cars will be to adopt all of the positive attributes of the best human drivers without any of the distractions or physical shortcomings. Managing the horn is one piece of the puzzle. 

As more self-driving cars hit the streets, like nuTonomy's recently launched trial with Lyft in Boston, fellow motorists will need to practice patience. Maybe we should be prepared to treat an encounter with vehicles laden with sensors and cameras the same way we handle intersections with clearly marked student driver cars: Give them a wide berth and some extra attention when they're nearby. Just don't expect the robots to thank you with a wave before speeding away.