Law enforcement agencies such as traffic police need to develop a system for instructing self-driving cars to stop or follow other orders, according to a report by global policy think tank the RAND Corporation.

The think tank, which today published the report outlining how technology could shape future policing and criminal justice, said that law enforcement needed to start giving the issue serious thought now so that they are not overwhelmed when driverless cars begin to see widespread use in a few years time.

“Just how will an officer signal instructions to self-driving cars, such as when officers are controlling traffic at intersections?” said John S Hollywood, lead author of the report and RAND senior operations researcher.

“This and many other questions about law enforcement and driverless vehicles need to be addressed.”

In the report, the think tank outlined a potential future scenario where a police officer would want to stop a vehicle, in this case to direct the flow of traffic:

“The police officer directing traffic in the intersection could see the car barreling toward him and the occupant looking down at his smartphone. Officer Rodriguez gestured for the car to stop, and the self-driving vehicle rolled to a halt behind the crosswalk,” Hollywood and his fellow authors wrote.

“The officer waved the car on as the oblivious passenger continued checking his email. But he wasn’t oblivious for long. A very human-driven sport-utility vehicle (SUV) barreled through the intersection, forcing the officer to dive for safety and the automated car to brake hard and swerve to avoid a collision.”

In this example, the self-driving car’s need to take orders is shown in a positive light – a simple procedure with little impact on the vehicle’s occupant – while the human driver is portrayed as the dangerous criminal element.

However, such powers would also mean police could – in theory, at least – instruct a driverless car to stop if it contained a suspect in an ongoing investigation, a wanted criminal, or even, perhaps more concerningly, someone the police offer suspected of being an illegal immigrant.

Hollywood stressed that any such powers would need to be decided on in a way that doesn’t enable the police to overstep their powers – a serious challenge for whoever is tasked with making this system work.

“There needs to be agreed upon limits on some of the technologies so that they are not used to limit the privacy and civil rights of innocent people,” he said.

“In addition, there need to be security standards to make sure that as more information is collected, the information is adequately protected from hacking.”

However, there is also the challenge of creating a consistent system across different types of driverless cars.

With brands as diverse as Google and Mercedes involved in self-driving car development, and now with Apple getting involved, a system that works the same no matter who the developer is will require significant collaboration to achieve.