Mercedes-Benz launches autonomous city bus
Friends who work in Daimler Buses sometimes express regret that their company does not appear to be keeping pace with European competitors on the development of transit buses with alternative fuels and driveline technology. I can understand their concerns, but the company has forged ahead with very strong sales of diesel-engined Mercedes-Benz Citaro city buses with the latest Euro 6 engines. They have minimal exhaust emissions and superior fuel consumption to previous generations. Production of the Citaro is fast approaching 50,000 units, an all-time record for a modern-generation city bus.
That is not to say that Mercedes-Benz has been solely focused on diesel. They have built hybrid buses and they have the largest number of fuel-cell buses in operation in Europe, in countries like Germany, Italy and Switzerland. They launched the option of a modern compressed natural gas (CNG) engine just one year ago.
However, Daimler Buses accelerated past all its competitors in an event in Amsterdam, The Netherlands, in July this year, when it launched the world’s first full-sized semi-autonomous transit bus. The project was sufficiently well advanced to be shown to leading customers and the trade press.
Daimler Buses has the advantage of being able to work with colleagues in the car and truck divisions on advanced technology, like autonomous vehicle control, fuel cells and all-electric vehicles.
The Netherlands is moving faster than other European countries in promoting advanced automotive technology and zero emissions. Earlier this year, convoys of heavy-duty trucks ran in platoons from the home cities of their manufacturers to the port of Rotterdam. They had inter-linked GPS and electronic systems. Running at the same gross weight they could travel closer together, ensuring valuable savings in fuel consumption. Although each vehicle had a driver, for safety reasons, the platoon was under the control of the leading truck.
The City Pilot bus project was demonstrated on a segregated busway linking Amsterdam’s Schipol airport with the town of Haarlem, serving stations along the route. Those stations have platforms that are level with the low floors of the city buses. Most of them in service, running every two to three minutes, were articulated Mercedes-Benz Citaro models. Just to be clear, there were no guide wheels helping to control the wheels, nor any white lines on the road surface.
Mercedes-Benz took parties of around 30 journalists at a time on a round trip on the system, covering approximately 20 miles. The bus was equipped with global positioning systems, also a combination of radar detection and cameras which monitored everything that was happening every second, not only in front of the bus, but alongside and behind it. The radar could see more than 200 yards ahead.
The cameras had closer vision and were inter-connected, giving a precise picture of the surroundings and the exact position of the bus. Near the top of the front pillar on each side, a small external camera monitored what was happening alongside and behind the vehicle. This was relayed to larger mirrors inside the bus, mounted quite high on the windshield pillars. The interior displays were totally free from any distortion by rain, road dirt or icing in winter conditions.
There was a normal driver’s position on the off-side front, complete with instrument displays, a steering wheel and foot pedals. The driver was there only for safety reasons. He only took control of the steering wheel when approaching and passing a bus travelling in the opposite direction and that was a local safety regulation.
Travelling on the City Pilot was an amazing experience. I sat near the front, on a seat facing the driver. The bus accelerated quite rapidly, with very smooth gear changes. It almost immediately entered a tunnel about 1-mile long, when the GPS was inactive but it was still able to follow bends in the tunnel and keep exactly on course. At times, between stations, it reached speeds of up to 50 mph but when it approached a station it decelerated remarkably smoothly, parking within 4 inches of a platform level with the floor. This enabled passengers to get on and off rapidly.
In various places along the route, it was intersected by streets used by other traffic. These were controlled by traffic lights. The bus could send an advance signal to the traffic lights, ensuring priority and therefore faster average speed. It could also recognise pedestrians who might want to cross the track just in front of the bus at the last minute, usually to catch a bus going in the opposite direction.
Mercedes-Benz said that the City Pilot system did all the driver’s work, saving him or her from stress and effort. At this early stage in the development in autonomous buses, a driver still has to be present, and that is reassuring to passengers. He or she can override the system in the event of an emergency but at the end of a shift a driver should feel much more fresh. Passengers will benefit from very smooth travel and there should be savings in fuel consumption from optimum control of gear changing, acceleration and braking.
It is well known that Mercedes-Benz is planning a next generation of city buses. There will be a common platform capable of using standard diesel, hybrid, gas, all-electric and fuel-cell hybrid drive systems. These are likely to be introduced around 2018-2019, following a further investment of around $200 million. The company plans that the option of autonomous driving will be available from 2020.
The City Pilot Citaro was also a design and development test-bed for the Bus of the Future. The design team took a standard Citaro city bus and modified it heavily, with many new ideas, to stimulate customer reaction.
Most Citaro buses have one double-width entrance in front of the front axle, opposite the driver, and a second double-width door ahead of the rear axle. To a large extent, this layout has been dictated, not only on the Citaro, but many other European buses, by the need for the driver to collect fares or ensure that the passenger uses a valid automatic payment system.
The design team opted for two double-width doors in the center of the bus in mid-wheelbase. They reckoned that this will greatly improve passenger flow, especially at busy stops. On entry, passengers could validate tickets or pay for their journey by suitable cards at a centrally mounted machine. They could turn left and go towards a rear lounge area with side facing seats and another bench across the rear face, giving a club-type atmosphere. Alternatively, they could turn right moving towards the front, where there were further inward facing seats, including one almost opposite the driver. Passengers on short journeys could cross the gangway to another row of side facing seats.
I have reservations about the number of sideways-facing seats, partly because they reduce the overall seating capacity, but also because passengers could bump into one another if the vehicle had to brake sharply. There was also a noticeable shortage of hand rails for standing passengers, or for those with disabilities moving around the bus. They are comments that are likely to be picked up during customer surveys but I cannot help feeling that many will call for more conventional forward-facing seats.
Externally, the styling was dynamic. Although the frontal aspect was clearly derived from the highly popular Citaro, the traditional waist rail on each side was replaced by swooping curving glass, letting more light into the vehicle. Matte-black panelling at various points tended to make the area of glazing look even larger. Attracting fairings at roof level neatly disguised the air conditioning. A strip of full-width lighting, on the front and the rear faces, could illuminate in blue or white, indicating when the vehicle was or was not running in autonomous mode. It might take some time to get that idea accepted by European legislators.
It was an unusual experience to sit in a 40-feet transit bus running in autonomous mode. Talking to the drivers, they admitted that they had at first been wary of the technology, but quickly became convinced by it. Some journalists thought that drivers would become bored if their work was taken over completely by the autonomous driving system. They thought there was a risk that they might be distracted and fail to notice any emergency situation where they had to manually override the system. While I can understand their concern, I feel quite confident that drivers will trust the systems and appreciate an easier-driving environment. Although the test in the Netherlands was carried out on a separate right of way, the real test will probably come when autonomous buses are introduced to city streets, mixing with much more traffic, pedestrians and other obstacles.
Doug Jack is with Transport Resources in the United Kingdom.