Buses from Daimler Buses: safely equipped for the future

• The integral safety concept of Daimler Buses
• Extensive safeguards against COVID-19 transmission
• Active Brake Assist 5: another milestone in the evolution of safety
• Preventive Brake Assist: the braking assistance system for city buses
• ESP introduced at an early stage in series production, ATC for articulated buses
• Sideguard Assist: the first turning assistant for buses
• Front Collision Guard and Crash Element – superb passive safety

Stuttgart. Daimler AG has assisted bus drivers for a number of years now with increasingly sophisticated and effective assistance systems because the greatest possible levels of safety are the central focus of research and development at the Stuttgart-based corporation. The current vehicle generations from Mercedes-Benz and Setra include, among other things, Active Brake Assist 4 (ABA 4), Preventive Brake Assist and Sideguard Assist which are true benchmarks in the fields of active safety. In the new Mercedes-Benz Intouro, Active Brake Assist 5 (ABA 5) has been introduced, a first in buses worldwide. Special protection measures against infection provide a very different type of safety for new buses and also for retrofitting.

The integral safety concept of Daimler Buses

Safety in buses from the Mercedes-Benz and Setra brands isn't just about individual measures; rather, the brands implement a comprehensive and integral safety concept. The claim that stems from this approach could not be clearer: both bus brands should fulfil the highest demands on safety and continue to drive forward development in all fields. The integral safety concept comprises numerous modules, with the focus on a number of vehicle and application-specific safety innovations which seek to enhance active and passive safety on an ongoing basis. This concept is supported by a range of further measures such as driver training, in which drivers are taught how to recognise dangers in good time and avoid taking risks. They are also shown how to react correctly in the event of an accident. The concept also involves informing passengers on how to use the on-board safety equipment – starting with putting on their seat belts. It goes far beyond this, however, and also includes responsible vehicle maintenance and the use of tried and tested Genuine Parts when the vehicle comes in for a service. The aim of the integral safety concept is an ambitious one: to realise the vision of accident-free driving.

Extensive safeguards against COVID-19 transmission

The extensive protection measures for drivers and passengers against infection in the face of the COVID-19 pandemic provide a very special kind of security. No matter whether vehicles are from Mercedes-Benz or Setra, are scheduled buses or travel coaches: they can be equipped with driver protective doors, high partitions behind the driver and in the entrance area, and contact-free disinfectant dispensers. Buses with air conditioning boast active high-performance particulate filters with an anti-viral functional layer. These active filters are also installed in the air conditioner housing as standard. In any case, passengers and drivers benefit from the continuous rapid exchange of air in the vehicle interior every few minutes. It takes place much faster than is required in offices, for example. The combination of the active filters together with the rapid exchange of air minimises the risk of infections from aerosols. Existing vehicles can be retrofitted with many of these measures.

Active safety: Mercedes-Benz and Setra are traditionally pioneers

The anti-lock brake system ABS, ASR acceleration skid control and the retarder as a wear-free auxiliary brake, passive safety systems like FCG Front Collision Guard or current high-tech assistance systems like the electronic stability program (ESP): Mercedes-Benz and Setra have always been pioneers in safety and assistance systems. Nearly all these systems had their premiere in a Mercedes-Benz or Setra.

The ergonomically perfect operation, the mirror systems, and the suspension which is both dynamic and comfortable with astounding agility and a surprising small turning circle in all versions, are also exemplary.

ABA 4 as standard for touring coaches from Mercedes-Benz and Setra

The emergency braking system Active Brake Assist, or ABA, shows the prominent role played by safety for Daimler Buses. The first generation was presented in a Mercedes-Benz bus as a world premiere in 2008 and it has been continuously refined since then. Today, Active Brake Assist 4 is standard equipment in all touring coaches of Mercedes‑Benz and Setra: in the Mercedes‑Benz Tourismo as well as in the Setra ComfortClass 500 and TopClass 500 including the double-decker Setra S 531 DT.

ABA 4 is based on a radar system and can automatically carry out a full-stop braking manoeuvre, within the system's limits, to bring the vehicle to a standstill to avoid a stationary or moving obstacle. As the first system of its kind worldwide, it also warns the driver of imminent collisions with moving pedestrians and simultaneously initiates automatic partial braking. This gives the driver the possibility of avoiding the collision by means of maximum full-stop braking or a steering manoeuvre.

Active Brake Assist 5: another milestone in the evolution of safety

Now the next generation of Active Brake Assist is entering the race. The new Mercedes-Benz Intouro is the first bus from Daimler Buses to be based on an enhanced electrical/electronic platform. Among other things, it forms the basis for the latest generation of assistance systems. For example, the Intouro is the first bus to feature the emergency braking assistance system Active Brake Assist 5 – or ABA 5 – another milestone in the evolution of safety.

In its fifth generation, Active Brake Assist reaches another peak of performance. For the first time, ABA 5 works using a combined radar and camera system. The optionally available assistance system can, in addition to the previously known functions, even automatically execute a full-stop braking manoeuvre to avoid a moving person. ABA 5 can identify moving pedestrians as well as people who suddenly stop and stand still. In practice the process is as follows: if there is a risk of a collision with a pedestrian, Active Brake Assist 5 provides the driver with visual and acoustic warnings and simultaneously initiates a partial application of the brakes. If the driver fails to respond, an emergency braking manoeuvre follows automatically, bringing the vehicle to a standstill.

Preventive Brake Assist: the braking assistance system for city buses

Preventive Brake Assist introduced by Mercedes-Benz is the world's first active brake assistance system for city buses. The assistance system warns the driver about a possible collision with moving pedestrians as well as with stationary or moving objects, and in case of an acute risk of collision automatically initiates a braking manoeuvre with partial braking. The warning cascade and braking intervention are designed for use in urban traffic.

Preventive Brake Assist is similar in its function to Active Brake Assist 4. It is adapted to suit the highly dynamic traffic situation involved in urban bus operations, with numerous different road users going in all directions. In the event of an imminent collision, Preventive Brake Assist alerts the driver both visually, with an illuminated red triangle and vehicle icon in the central display, and audibly, and at the same time carries out partial braking. This braking intervention is maintained until either the driver intervenes or the bus comes to a stop. The driver can override a system intervention at any time by operating the brakes, steering to avoid an obstacle or by using the accelerator or the kickdown function.

Preventive Brake Assist deliberately does not carry out an automatic maximum full-stop braking manoeuvre. This reduces the risk of injury to passengers standing in the vehicle and for those who are seated but not wearing seatbelts. However, the driver always has the option of applying the brakes fully themselves if this is required. Warning and braking reactions to stationary and moving obstacles occur over the entire speed range of the bus. Pedestrian detection is activated up to 50 km/h.

Preventive Brake Assist is optional for the whole model family of the
Mercedes-Benz Citaro and also for the Conecto.

ESP introduced at an early stage in series production, ATC for articulated buses

In April 2002, Daimler Buses introduced the optional electronic stability program (ESP) to its line-up and was the first bus manufacturer to do so. Then, in October 2003, it was adopted as standard equipment for touring coaches. The ESP driving dynamics regulator operates up to the limits of the physically possible with the aim of reducing the risk of skidding by a significant margin. Based on information such as the turning angle of the front wheels, the vehicle speed and the lateral acceleration, a sensor detects potentially dangerous driving situations. To avoid danger, the engine torque is reduced and, following this, individual wheels are braked by precisely the right amount to prevent dangerous instability.

At the same time, Daimler also introduced Brake Assist (BA). It identifies an emergency braking situation by the speed at which the brake pedal is operated and immediately applies a significantly higher brake pressure. This reduces the stopping distance and thus helps to prevent accidents.

The Mercedes-Benz Citaro was the first scheduled service bus to be available with ESP. For the Citaro G articulated bus too, the Daimler Buses engineers found a solution. Articulated buses are very demanding in terms of driving stability, because the drive in the rear section pushes the front section. Mercedes-Benz responds to this with hydraulic dampening of the articulation joint, thus preventing uncontrolled bending of the joint. The latest evolution is the patented articulation angle control system Articulation Turntable Controller (ATC). The articulated buses with the three-pointed star thus achieve the best possible driving stability, almost on the level of ESP. The dynamic ATC regulates the hydraulic dampening of the articulation joint quickly when and where it is needed. It takes numerous parameters into account. If the vehicle reaches a critical condition, such as on slippery or wet roads, ATC initiates the necessary dampening of the articulation joint in a split second. The two damper cylinders are activated independently of each other. The articulated bus is then very quickly stabilised within physical limits, preventing the vehicle from rocking or even the rear section swinging out. All articulated buses from Mercedes-Benz are equipped with the ATC anti-jackknifing system as standard.

Autonomous intelligent cruise control maintains the right distance

The autonomous intelligent cruise control feature (AICC) takes the strain off the driver on arterial routes and motorways. If the system detects a slower-moving vehicle in front, it brakes the bus automatically until the safety distance pre-programmed by the driver is achieved and then maintains this distance. Multi-mode radar is implemented for this purpose. If there are no vehicles in front, AICC works like a conventional cruise control system. Autonomous intelligent cruise control assists the driver, especially in medium to heavy traffic on main roads, and largely eliminates the need for adaptive braking. Deceleration is limited to approx. 20 percent of the maximum braking power. If a situation requires greater deceleration, Active Brake Assist is activated.

Autonomous intelligent cruise control (AICC) with Stop/Start Assist (AHA) aids the driver in traffic jams or in traffic which is becoming increasingly slower. The additional "Stop-and-go" function extends the regulating range: if the vehicle is stationary for less than two seconds, the distance control function remains active in slow-moving traffic up to a speed of 15 km/h and then brings the touring coach back up to the set speed.

Lane Assist issues lane departure warnings

Lane Assist (SPA) uses a camera located behind the windscreen to detect if the vehicle is in danger of leaving the road. SPA constantly monitors the distance of the bus to the lane markings on the road. If the vehicle crosses the lane marking by the width of a tyre, the corresponding side of the driver's seat starts to vibrate to warn the driver. SPA is only active at speeds of over 60 km/h and can be deactivated by switching on the turn signal, for example to initiate an intended lane change.

Safe downhill driving at a constant speed with the continuous braking limiter

The continuous braking limiter decelerates the vehicle using the retarder when the statutory downhill speed limit of 100 km/h is exceeded. It is therefore practically impossible to inadvertently exceed the speed limit when driving downhill.

Sideguard Assist: first turning assistance system for urban buses and touring coaches

Turning off in urban traffic is among the most unpleasant tasks for drivers: Not only do they have to look forwards for traffic lights, signs, opposing and crossing traffic, but they also have to keep an eye on any pedestrians and cyclists who may be alongside the vehicle. Moreover, the traffic situation can change in seconds. Cyclists and pedestrians are also sometimes unaware that the bus or coach driver may not even be able to see them at all. Mercedes‑Benz and Setra are thus the first bus brands in the world that now offer Sideguard Assist with pedestrian detection.

Sideguard Assist has a multi-stage operating strategy: it initially warns the driver if a relevant object is located in the warning zone. In the second stage, the driver is warned if they fail to react or if their reaction is not continued and would thus otherwise result in the risk of a collision. If, when turning off, the sensors detect a stationary obstacle in the turning radius of the bus (for example: traffic lights or a bollard), a visual and haptic warning is also issued. This means avoiding collisions and expensive repairs. The turning radius warning is operational from a walking pace up to a speed of 36 km/h. The other functions of Sideguard Assist are available from a walking pace right up to 100 km/h.

Sideguard Assist can even do much more: at speeds above 36 km/h, it also provides the driver with warnings when changing lanes to the right-hand side. Here, the driver is also informed of any object on the co-driver's side and a warning is emitted if the driver activates the indicator.

Attention Assist monitors the attentiveness of the driver

Attention Assist is a safety system that constantly monitors information about the driver's activity using a variety of criteria such as steering movements and activation of the brakes, operation of the turn signals, as well as the vehicle speed and the time of day. Attention Assist correlates the data recorded and the adapted driver profile to determine the driver's ability to react and their level of fatigue. If a defined model value is exceeded, an electronic signal in the form of a vibration in the driver's seat is issued, reminding the driver to take a break. Passengers will be unaware of this.

More safety thanks to LED headlamps

Mercedes-Benz and Setra touring coaches can optionally be equipped with the world's first integrated LED headlamps for buses. Drivers benefit from light which is less tiring on the eyes: the colour temperature of the light from LED headlamps is very close to that of daylight. The innovative lighting technology thus increases active safety and also ensures great vision even in adverse weather conditions. A further safety feature: the level of light emitted from an LED lamp remains almost exactly as high across its entire service life. This service life is many times longer than that of halogen or xenon lamps. Several bulb changes are thus no longer required, and their associated costs and downtimes can also be dispensed with.

Front Collision Guard and Crash Element – superb passive safety

If an accident should occur despite all the assistance and safety systems, buses from Mercedes-Benz and Setra provide the best possible protection. Front Collision Guard (FCG) is a unique passive safety system to protect the driver and passengers in the case of a head-on collision. Front Collision Guard consists of a complex safety system. It starts with a cross-member which forms an underride guard in the event of an accident in the interests of partner protection and can, for example, prevent a car from passing underneath the vehicle. The structure behind this member consists of crash elements that specifically dissipate kinetic energy in the event of an impact.

In addition, the driver's workstation within the bus, including steering, pedals and seat, is mounted on a solid frame component that can move back completely in the event of a serious head-on collision and thus increase the survival space by a significant amount of centimetres. The developers carried out practical crash tests on the effect of Front Collision Guard. FCG also already fulfils future legal standards for pendulum impact tests on buses.

An outstanding safety feature in the extended front end of the Citaro is a crash element which provides additional protection in a collision. It largely corresponds to the revolutionary Front Collision Guard of touring coaches. Combined with the reinforced A-zero pillars and a defined frame structure which steers impact forces directly to the substructure in a collision, the Citaro even conforms voluntarily to the swing-bob impact test for touring coaches as specified in the European regulation ECE R 29.