How many self-driving vehicles can one person monitor at the same time?

It is possible for one person to safely monitor up to five self-driving vehicles at once, according to new research led by Coventry University.

As self-driving vehicle trials expand across the UK, having trained people to intervene remotely if something goes wrong is essential for both safety and reliability.

This kind of remote oversight is likely to be used for services such as driverless buses, delivery vehicles and robotaxis, where one person monitors several vehicles as they follow fixed routes. It doesn’t apply to private self-driving cars, where a driver would currently need to be in the vehicle and in control.

Monitoring several vehicles at once could improve efficiency, cut costs and reduce the risk of accidents, but only if we understand how many one person can safely supervise without losing focus or becoming overwhelmed.

Researchers from Coventry University’s Research Center for Future Transport and Cities set out to find this limit by asking experienced drivers with limited monitoring experience to watch between three and nine synthetic self-driving cars on screens in a simulator of a control room, similar to setups planned for future transport networks.

The operators were instructed not to interfere with the driving, only to watch the cars across different scenarios and decide if a standby driver needed to step in when something looked wrong.

The study, published in the journal Computers in Human Behavior, assessed how quickly and accurately participants responded to potential issues, as well as the difficulty they experienced during the task.

Results showed that operators were most effective when watching around five vehicles, as it allowed them to react quickly and stay alert without feeling overwhelmed. On average, they took 13 seconds to respond, which is close to how long it takes to fully evaluate a situation before acting.

Performance stayed steady when operators monitored between five and seven vehicles but dropped considerably once they had to watch nine.

When supervising only three vehicles, some operators intervened too often, suggesting the task wasn’t challenging enough and may have led to over-alertness.

Operators said clear and timely information from the vehicles helped them make decisions, but too many messages became distracting. This suggests alternative ways to deliver information, such as audio or voice alerts, could improve focus and response times.

Professor Stewart Birrell, Director of the Research Center for Future Transport and Cities, said, “We’re proud to have provided insights that could support the safe rollout of connected and automated vehicles. This study was essential for understanding what remote supervision might look like in the real world. We found that five vehicles are enough to keep operations efficient without overwhelming the human operator.

“Having this knowledge and insight is critical if we want these systems to work in busy places like cities, where one person might need to keep an eye on several vehicles at once.”