The mother of all traffic jams could be on the horizon, and researchers at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, are working to create a crossing guard that’s up to the challenge.

The Federal Aviation Administration (FAA) estimates that by 2024, there will be more than two million commercial and recreational drones – also known as unmanned aerial vehicles, or UAVs – flying in the National Airspace System. Lanier Watkins, a senior cybersecurity research scientist in APL’s Asymmetric Operations Sector, and his team propose addressing this boom by deploying a set of autonomous algorithms capable of preserving airspace safety and directing traffic on this unprecedented scale.

The low-altitude airspace presents an opportunity, enabling routine autonomous operations such as search and rescue, precision agriculture, critical infrastructure inspection and medical delivery, according to Josh Silbermann, APL project manager of Airborne Collision Avoidance System X for small UAVs (ACAS sXu). But that opportunity is not without obstacles.

“Constructing a low-altitude traffic management framework in the spirit of our traditional air traffic control system is a challenge. The various networked components, which may have been independently designed, must work safely together,” said Silbermann. “Their interactions must be assured to avoid failure modes, especially as the individual decision processes become increasingly complex. Lanier’s team is taking this long view toward a more complex, dense and autonomous UTM [Unmanned Aerial System (UAS) Traffic Management] ecosystem.”

This work is an offshoot of APL’s longstanding collaboration with the FAA on surveillance and collision-avoidance standards, which date back multiple decades, primarily in creating standards for large manned aircraft. More recently, that work has extended to creating systems, such as ACAS sXu, designed to facilitate the entry of increasing numbers of unmanned craft into airspace traditionally dominated by manned craft. Systems populated entirely by UAVs present an even greater challenge, according to Silbermann — particularly as commercial entities enter the space, each with their own proprietary UAV designs and navigation systems.

Another key piece of the work moving forward is building additional levels of safety into the system, such as the ability to validate decisions and make on-the-fly adjustments to compensate for malfunctioning components.