Number one for safety: first bus worldwide to feature Active Brake Assist 4 and Sideguard Assist

• Setra – tradition-bound to maximum safety
• Fire extinguishing system as standard
• World first in the bus and coach segment: Active Brake Assist 4 brakes in response to pedestrians
• World first in the bus and coach segment: Sideguard Assist provides warnings during cornering and turning off
• Sideguard Assist also helps when changing lane

Buses are among the safest means of transport. Setra makes them even safer, the new Setra TopClass S 531 DT setting benchmarks with its assistance systems. The use of the Active Brake Assist 4 emergency braking system and Sideguard Assist on board the new double-decker marks the world premiere for these features in the bus and coach segment.

Setra – tradition-bound to maximum safety

ABS, ABA 4, ART, AtAs, BAS, DBL, ESP, TPMS and more besides – the scope of standard and optional equipment for the new Setra reads like an A to Z of the latest assistance and safety systems. This fits into a long tradition at Setra: in 1955 the brand was among the pioneers of independent wheel suspension on buses and coaches, in 1964 it was the first to introduce the retarder as a wear-free auxiliary brake and a few years later it championed disk brakes. Back in 1981 Setra was already optionally installing the ABS anti-lock braking system on all buses and coaches. In 1984 it became the first brand in Europe to fit ABS as standard. Introduction of xenon headlamps as standard in 2001 in the then new TopClass 400, followed in swift succession by the ESP Electronic Stability Program, adaptive cruise control, Continuous Braking Limiter, Lane Assistant and the Front Collision Guard – the highest safety standards courtesy of Daimler Group technology. Setra most recently introduced the option of integrated LED headlamps at the end of 2015.

As a result, the new double-decker buses even comes with LED headlamps as standard. The light from these headlamps is similar to daylight and is less tiring on the eyes. Their durability and their virtually undiminished luminous intensity throughout their service lives are additional benefits of relevance to safety.

Fire extinguishing system as standard

Traditionally safety is number one on the list of priorities for Setra, a fact underscored for example by the fire extinguishing system fitted as standard equipment in the new double-decker bus. Not required by law in touring coaches until mid 2019, in the S 531 DT the system is already included from the start of series production as part of the standard equipment.

The extinguishing process is activated via a loss in pressure in a detection line, e.g. due to intense heat. As part of this, the extinguishing liquid is forced through the nozzles of the distribution system and sprayed as a high-pressure water mist in the engine compartment. In this way the oxygen is dispelled within fractions of a second, thus depriving the fire of its supply basis. The surface of the components is cooled and the possibility of reignition effectively prevented. The extinguishing agent runs through the entire engine compartment. As part of this the individual nozzles are directed towards components which reach higher temperatures, such as the turbocharger, oil filter module and auxiliary heater for example.

The fire extinguishing system is certified by TÜV and already achieves advance fulfilment of the statutory provisions and test requirements pursuant to Regulation UN R107/06 Supplement 4, which will be binding for class 3 coaches first registered from 10.06.2019.

Pendulum impact test similar to ECE-R-29 complied with voluntarily

Active safety, i.e. accident prevention, is a prime concern for a double-decker bus with up to 83 passengers on board, hefty dimensions and a permissible gross weight of 26 t. Should an accident nevertheless occur, driver and passengers benefit from the highest possible standard of passive safety. The previous Setra double-decker bus already benefited from a reinforced framework following its comprehensive overhaul in the autumn of 2015, thereby voluntarily meeting the requirements of the pendulum impact test in accordance with ECE-R-29. Setra furthermore provides rescue services with online rescue data sheets for all its buses and coaches.

Emergency braking system Active Brake Assist can save lives

The emergency braking system Active Brake Assist (ABA) is an outstanding assistance system. Its original version was introduced in the Setra TopClass 400 around ten years ago, since when it has benefited from ongoing further development. The emergency brake assist system AEBS, which in the meantime has been prescribed by law for class 3 coaches, must already guarantee a significant reduction in speed in response to both moving and stationary obstacles. The current Active Brake Assist 3 (ABA 3) already significantly exceeds the requirements and also brakes the coach to a standstill by full brake application on detecting stationary obstacles. ABA 3 has been available for the Setra S 431 DT double-decker bus since 2015. Touring coaches with emergency brake assist system are thus not only able mitigate the consequences of a serious accident but are actually even able to avoid such accidents, within the given physical limits.

World first in the bus and coach segment: Active Brake Assist 4 brakes in response to pedestrians

A new chapter is now being written in the history of assistance systems: the Setra S 531 DT is the first bus in the world to feature the emergency braking system Active Brake Assist 4 with pedestrian detection – a further milestone in the development of assistance systems.

The outstanding feature of Active Brake Assist 4 is that it warns the driver of imminent collisions with moving pedestrians and simultaneously automatically initiates partial braking. It is the first system of its type worldwide to perform such functions. This enables the driver to avoid a collision by means of maximum full-stop braking or a steering manoeuvre.

Active Brake Assist 4 thus constitutes a further development of well-proven Active Brake Assist 3, incorporating an additional warning and partial braking to enhance the safety of pedestrians. Its mode of operation and displays correspond to ABA 3. Unlike when braking for moving and stationary obstacles, there is no warning cascade prior to partial braking for moving pedestrians: the acoustic and visual warnings occur at the same time as partial braking.

Long- and short-range radar systems detect pedestrians, cars and objects

The long-range radar of Active Brake Assist 4 detects vehicles and obstacles in a direct line in front of the bus up to a distance of 250 m and pedestrians up to a distance of 80 m. Motorcycles, mopeds and cyclists are detectable up to a distance in between these two ranges (160 m). The maximum beam angle is 18 degrees. The short-range radar has a range of 70 m. The wide beam angle of 120 degrees additionally enables Active Brake Assist 4 to detect vehicles and moving pedestrians at the sides of the area in front of the vehicle, whereby the range of vision is dependent on the topography, the course of the road, weather conditions and ambient influencing factors, such as pedestrians moving quickly into the traffic area or concealed pedestrians.

Active Brake Assist 4 is able to detect moving pedestrians in virtually any traffic situation, for example if they cross the bus's lane, emerge from behind an obstacle or are moving along the vehicle's lane. Pedestrians are also detected within the range of the radar system when the vehicle turns off to the left and right. The warning and braking reactions to stationary and moving obstacles are effective across a speed range from 0 to 100 km/h, while the automatic warning and braking reactions of the pedestrian detection system apply up to a speed of 50 km/h.

The bus driver then decides on any further actions. The driver can override the system at any time as necessary, by means of a steering movement, kickdown or emergency braking, for example. If the driver does not brake firmly enough, the braking intensity of Active Brake Assist 4 takes precedence.

Multi-mode radar with improved range and performance

The basis for Active Brake Assist 4 with the additional pedestrian detection function is provided by a new generation of radar technology. This is also used in the current passenger cars and trucks from Mercedes-Benz, demonstrating the close cooperation within the group.

The advantage of a radar system is that it operates independently of the prevailing light conditions and also largely independently of weather conditions. Radar determines distances and relative speeds extremely precisely, and is also able to "see" at night and in rain and fog. Vehicles, pedestrians and objects are recognised on the basis of a radar signature. This involves analysis first and foremost of the form and reflection.

The new radar generation takes the form of electronically scanning multi-mode radar. This offers markedly improved range and performance. For the first time, the long-range radar now operates independently of the set driving level and is able to adapt continuously to changing inclination of the vehicle as a result of suspension or load statuses.

World first in the bus and coach segment: Sideguard Assist provides warnings during cornering and turning off

Right turns in urban traffic are among the least pleasant tasks for drivers, as they are required to heed traffic lights and signs ahead while simultaneously observing oncoming and crossing traffic and keeping an eye on pedestrians and bike riders at the side. In addition, the traffic situation can change in a matter of seconds, and cyclists and pedestrians are not always aware that a bus driver may possibly not be able to see them. With this in mind, Setra is now the first bus and coach brand to offer the Sideguard Assist with pedestrian detection. Available for a year now on board Mercedes-Benz trucks, the time is currently ripe to introduce Sideguard Assist for buses and coaches as well.

The objective: continual information, warnings as necessary

Sideguard Assist operates in several stages: it first of all informs the driver when a relevant object is located in the warning zone. In a second stage the driver receives a warning if they initiate or continue an action and a danger of a collision arises.

If there is a moving object in the side monitoring zone the driver is provided with a visible warning. An LED in the shape of a triangle lights up at the driver's eye level in the outside mirror on the co-driver's side. The lamp draws the driver's attention intuitively towards the situation alongside the vehicle. If the sensors detect the risk of a collision, an additional visual warning is given: the LED flashes brightly several times in red. After two seconds, it remains permanently illuminated in red. A haptic warning in the form of a vibration in the driver's seat is additionally provided, as with the Lane Assistant.

A visual and haptic warning also occurs if the sensors additionally detect a stationary obstacle, such as a traffic light or a bollard, in the bus's turning curve during cornering. Collisions can be avoided in this way. The tracking pattern curve warning system functions from walking pace up to 36 km/h. The other functions of Sideguard Assist are available from walking pace up to 100 km/h.

For the purposes of its warning cascade, Sideguard Assist also analyses actions by the driver, for example activation of the indicator on the co-driver's side or the steering movement when moving off, and the distance from a moving or stationary object is assessed continuously while the truck is on the move. Sideguard Assist also warns the driver of any obstacles when they turn off without activating the indicator, for example.

The driver retains full responsibility and remains in control of the situation at all times and is able to take any course of action which appears appropriate.

Sideguard Assist also helps when changing lane

The new Sideguard Assist offers even more functions: at speeds above 36 km/h and up to the maximum permissible speed it provides the driver with warnings as an assistance system during lane changing. The driver is also informed of any object on the co-driver's side and a corresponding warning is output if the driver activates the indicator. This means that Sideguard Assist provides support when changing lane, for instance when overtaking a cyclist in an extra-urban setting, or when changing lane on multi-lane roads.

The radar sensors monitor the entire area on the co-driver's side

The core of Sideguard Assist is a radar sensor system with two short-range radar sensors in the wheel arch of the front axle on the co-driver's side. The side monitoring zone has a width of 3.75 m. The system is oriented so as to cover the entire length of the bus. Its range additionally covers the area two metres in front and behind the vehicle. Above 36 km/h, the scanned area is increased to up to 5 m to the front and as much as 15 m to the rear, in the interests of safe lane changing.