So long, AB1: the world’s first driverless bus will halt services early next year — but it appears the route from Edinburgh to the north side of the Forth Bridge hasn’t been running autonomously all the time.
Bus operator Stagecoach said the driverless project just outside Edinburgh, Scotland was coming to an end on 14 February 2025 because “the current phase of research, development and match funding comes to an end”, but also that “passenger adoption did not meet expectations”. However, customer comments posted online suggest the bus was frequently operating in manual mode with a human driver, suggesting technical or operational challenges.
The £6.1-million project “CAVForth” project has five autonomous buses running a route from the western edge of Edinburgh to just across the famous Forth Road Bridge.
Journalists were taken on a trip across the bridge in May 2023 — myself included — to show off the technology ahead of access to the public. While the bus had a safety driver at the wheel, he dutifully raised his hands away from the wheel while the autonomous mode was engaged to show the vehicle managing that portion of the route on its own.
Though the project promised capacity for 10,000 riders weekly, it’s perhaps not a surprise that the AB1 (for “autonomous bus”) route wasn’t busy given its hourly, limited route of just three stops on weekdays; that’s significantly less than was initially planned, with service every half hour seven days a week.
The 14-mile route runs from Edinburgh Park — a train station by an industrial park on the outskirts of the city — through Queensferry before trundling over the bridge to a park and ride on the other side.
At the press launch, I was told there were hopes to expand the route north to Dunfermline, which might have given AB1 a fighting chance.
Driverless bus in manual mode
But lack of demand may not have been the only challenge: the timetable for the AB1 route shows the bus has been operating in manual mode, rather than autonomously, though it’s unclear when that began. “AB1 is currently running in manual mode while we conduct ongoing improvement — check back for updates,” the website reads.
The public service began in May 2023, but it wasn’t long before it was running in manual mode. One post from a bus spotter in October 2023 reported it wasn’t in autonomous mode because of “safety concerns after an incident”. Messages posted on X.com by the local Stagecoach division in East Scotland confirm the bus wasn’t in autonomous mode at the end of October 2023, but returned to driverless services a few weeks later after a “successful software update.”
That pattern appears to have continued, with Stagecoach posting that the bus was again “being driven by a human” the following month, with the message reposted weekly throughout December 2023, with a final message saying autonomous service would return in the new year.
But in February 2024, another rider posted that the route was in manual mode again, and again in April, and again in August. “The service is usually autonomous for the full journey, however AB1 is currently running in manual mode while we conduct ongoing improvement,” the official X.com feed for Stagecoach East Scotland said in April.
Most recently, a rider posted in November saying that they take the bus twice weekly, but it hasn’t been autonomous for as long as a year.
By the time of publishing, neither Stagecoach nor engineering partner Alexander Dennis had as yet returned email requests for an explanation of why the bus was running in manual mode or whether it might return to autonomous services before the route was halted in February.
Sorry driverless fans, that means it may already be too late to head to Scotland to ride the world’s first autonomous bus.
Always just a driverless trial
The demise of the CAVForth project — or at least this particular route — highlights the hype that can come alongside driverless trials. At the time, headlines proclaimed that “driverless buses are now plying UK roads” — it was just the one — and claimed that driverless buses could become a “huge UK export opportunity”.
But this was always really merely a technology trial, so it’s no wonder that it’s coming to an end or that the system was at times inconsistent — and nor is it a surprise for a much-hyped technology like driverless to have plenty of details for the press at the launch and so little at the end.
In a statement, Stagecoach said: “We are proud to have achieved a world-first with this service, demonstrating the potential for self-driving technology on a real-world registered timetable in East Scotland.”
“Although passenger usage on the AB1 route, linking Ferrytoll with Edinburgh Park did not meet expectations and therefore will not be directly replaced, the trial has significantly advanced the understanding of the operational and regulatory requirements for autonomous services, delivering what was expected from this demonstrator project,” the statement continued.
At the press launch, the companies running the trial — including tech partner Fusion Processing — said the aim was to collect as much data as possible about how the bus, including how the system performed in inclement weather, how passengers felt about the ride, and the benefits offered by autonomy, with hopes it would save on petrol and maintenance.
Indeed, the team told me that alongside driver feedback after a shift, the system records whenever the driver has to retake the wheel, in order to understand why human intervention was needed — and that includes whenever the driver beeps the horn.
Driverless bus with double the staff
The autonomous bus wasn’t strictly speaking driverless in the sense of not having a driver at the wheel — in fact, two members of staff were always on board. First, for legal reasons and technical limitations, a driver was required to sit at the wheel and pay attention. Second, a “captain” was on board to assist passengers, answer any questions, and check tickets.
The CAVForth team stressed at the press launch that Stagecoach intended to always keep at least one person on board for future commercial deployments, saying the benefit of a driverless system wasn’t staff savings but reducing fuel and maintenance costs, and improving running times. Whether that was worth the increased costs from all the sensors and data processing is a question that remains unanswered.
At the press demonstration, the driver managed the exit from the depot but handed over control while the bus traversed the Forth Bridge; we were told it could manage 90% of the route autonomously.
However, they must keep attention at all times, keeping their hands on the wheel — though they were told to rest their hands rather than grip the wheel, to conserve their energy. By tapping the brake pedal, the bus would flip back to manual control.
How to make a bus driverless
The level-four driverless buses in question were a fleet of four Alexander Dennis Enviro200AV buses, with a fifth acting as backup. The single-decker buses were controlled by Fusion Processing’s CAVStar automated drive system, pulling in data from three LIDAR sensors, as well as cameras and radar.
The environmental data pulled in by the various sensors is interpreted by the control systems — there are two plus a third for backup — that decides what actions need to happen (such as turning the wheel, accelerating, braking), and that is then passed to a third system that directs the drive-by-wire controls that steer the vehicle.
Beyond setting up the bus, the CAVForth team also prepped the route, adding extra CCTV to watch over the route, repainting road markings to make it easier for cameras to spot them, and even upgrading to smart traffic lights, so they could alert the bus to upcoming red lights in advance.
Stagecoach added that though the AB1 route was coming to an end, it aimed to give it another go. “The partners remain committed to exploring new opportunities for self-driving technology in other areas across the UK, ensuring that this exciting innovation can play a transformative role in future transport networks,” it said.
Hopefully the world’s second autonomous bus route travels somewhere people actually want to go.
