Maintaining autonomous buses

Bus & Coach
Despite the use of cutting-edge technology in instrumentation and control, service and maintenance tasks on driverless buses are much more down to earth, finds Steve Banner

Self-driving buses are now going backwards and forwards on a 14-mile scheduled service that crosses Scotland’s Forth Road Bridge near Edinburgh.

Operating seven days a week, the five Alexander Dennis Enviro200AV diesel single-deckers are at the heart of the CAVForth trial led by autonomous automotive technology specialist Fusion Processing using its CAVstar technology. As well as Alexander Dennis, the project’s partners include Stagecoach, Transport Scotland, Edinburgh Napier University and Bristol Robotics Laboratory. The scheme is co-funded by the UK government’s Centre for Connected and Autonomous Vehicles.

Departing from the Ferrytoll Park and Ride in Fife, and heading for Edinburgh Park station and its adjacent retail outlets every 30 minutes at speeds of up to 50mph, the buses are based at Stagecoach’s Dunfermline depot. The route they are on encompasses A-roads, motorways and bus lanes and includes roundabouts and traffic lights; and lots of other vehicles.

So far as autonomous capability is concerned, they are at SAE Level 4, with a safety driver onboard at all times who can take control if necessary.

One possible benefit of adopting autonomous vehicles could be lower repair and maintenance bills as well as falls in energy costs, says Jim Fleming, marketing director at Fusion Processing. “Your brakes and tyres could last up to 25% longer and your fuel bill could fall by around 25%, too,” he suggests.

That is because the system that delivers the autonomy is optimised to ensure best driving practice, he says. “Remember that it is aware of every millimetre of road, and every microsecond of time,” he comments.

As a consequence the vehicle will be driven smoothly and frugally, minimising component wear and ensuring that its range between recharges is maximised as fleets switch to battery-electric technology.

By contrast, the capabilities of human drivers vary hugely. Some are exemplary and concentrate hard on what is happening ahead and around them, some are quite the opposite, while the remainder drift around somewhere between the two extremes. These variables are reflected in the price operators pay to keep their vans, trucks, buses and coaches on the highway.

The Enviro200AVs come with an array of sensors including radar, LiDAR, cameras and ultrasound, along with satellite navigation to detect and avoid objects in all weathers, day and night, and to plan an optimum path for the vehicle. They also receive information from traffic lights to enable them to travel at the right speed to get from one green light to the next.

Although they affect the accelerator, brakes and steering, none of these items include moving parts, and do not require regular servicing. What they do need however is monitoring, and periodic inspection to ensure they have not been damaged and are functioning properly.

Self-driving or not, Stagecoach buses are subject to a day-long inspection every 28 days and undergo a daily walk-around check before they venture on to the highway. Any faults spotted during the working day are recorded on a defect card for appropriate action.

The end of the working day so far as autonomous vehicles are concerned involves the completion of a standardised template which is sent to Fusion digitally.

Its contents are included in a weekly summary which goes to Stagecoach’s directors so they know how the buses are performing, and are reviewed every four weeks by the company’s health and safety director.

Alexander Dennis and Fusion keep a close eye on the vehicle, with a Fusion engineer present and weekly checks carried out. “The vehicle goes over a pit to ensure for example that the steering, which has lots of torque and steering angle sensors, is functioning as it should,” Fleming says.

Because they are in many respects conventional vehicles, the Enviro200AVs are maintained in the usual way, with the familiar cycle of engine oil, air and filter changes, AdBlue reservoir top-ups, and so on. Headlights and indicators must be checked, and wheelchair ramps must be cycled to ensure they do not stick.

Yet although the new technology has not resulted in additional servicing work, it has led to some unexpected tasks for Stagecoach employees.

“One thing Stagecoach has had to do is to provide staff with cleaning poles to ensure optical sensors on the roof are cleared of dead flies during the summer months,” Fleming observes. It has also meant greater attention to ensure that the routes buses are deployed on are kept clear of overhanging branches that could result in rooftop sensor damage.

Next year will see the route extended to the centre of Dunfermline, and the addition of an autonomous electric Enviro100AEV single-decker to the fleet.


Scotland is not the only location for a trial of autonomous passenger transport vehicles in the UK.

If you want to travel from Didcot Parkway station in Oxfordshire to the Milton Park business, science and technology park by public transport, you can now do so free of charge aboard a self-driving electric 15-seater shuttle bus built by Mellor. Covering around 100 miles daily, six days a week, on a 6.2-mile route with 18 stops, it is the first zero-emission vehicle of its type to be deployed in the UK.

The Mi-Link service is being delivered by the MultiCAV project. It, too, is part government-funded and uses technology from Fusion. The service is run by First Bus. Other organisations involved include the University of the West of England, Milton Park itself, plus Oxfordshire County Council.

Like the Scottish vehicles, the shuttle is inspected every 28 days, an exercise carried out at First’s Slough depot.

First Bus head of policy, John Birtwistle, makes the point that with a project like this, it is Fusion’s own engineers who are responsible for ensuring that the autonomous technology is working properly, rather than First’s technicians.

“If our guys find that a camera lens is cracked, for example, then they will of course draw it to Fusion’s attention,” he says. A Fusion engineer is present every day and the vehicle can of course be monitored remotely.

As with the Enviro200AVs, a driver is always sitting behind the wheel to assume control if the autonomous system develops a glitch. “If it is faulty, then the vehicle cannot go into autonomous mode anyway,” says Birtwistle.

“As it happens, we haven’t had any faults develop, and the bus runs autonomously for over 95% of the time,” he says. Occasions when it has not included when it encountered road works.

A full-size autonomous Switch Metrocity electric single-decker was about to be deployed as part of the scheme at the time of writing.

Is First finding the existing 15-seater is suffering less wear and tear than might be endured by a conventionally driven electric vehicle? “It’s hard to make a direct comparison, but what we haven’t seen is bodywork damage, even though it’s on the road for up to 12 hours a day,” says engineering and operations manager, Mudasar Ali. Benefits claimed for autonomy include better safety, and with all its sensors functioning, the bus should be able to avoid hitting street furniture or parked cars, or pedestrians and other vulnerable road users.

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