Buses and coaches from Mercedes-Benz: the alphabet of assistance and safety systems – always one star more

Dec 3, 2018
Stuttgart / Mannheim
  • The integral safety concept for buses and coaches
  • The Tourismo and Citaro: exemplary safety equipment
  • From A to S – the alphabet of safety and assistance systems
  • Preventive Brake Assist: the first active brake assist system for city buses
  • Sideguard Assist: first turning assistance system for city buses and touring coaches

The highest possible degree of safety is something that lies at the heart of the Mercedes-Benz brand. That’s why it has been supporting bus and coach drivers for many years with an increasingly wide range of effective assistance systems. At the heart of these is active safety for accident prevention. The many measures for mitigating the consequences of an accident are equally meritorious. But now Mercedes-Benz is raising the bar even higher: whether it’s the enhanced emergency braking assistant Active Brake Assist 4 (ABA 4) for touring coaches; Preventive Brake Assist, the first active brake assist system for city buses; or Sideguard Assist for city buses and scheduled service buses – they all far exceed the requirements laid down by law, all can save lives and all are world firsts. The alphabet of safety and assistance systems covers the gamut of technologies from Attention Assist to Sideguard Assist.

The integral safety concept for buses and coaches

For Mercedes-Benz, safety is a comprehensive, integral concept rather than a series of individual measures. The claim that stems from this approach could not be clearer: as a premium brand, Mercedes-Benz fulfils the most stringent of safety requirements and is forging ahead with its development activities in all areas. The integral safety concept comprises numerous modules, with the focus on a number of vehicle- and application-specific safety innovations, the aim being to enhance active and passive safety on an ongoing basis. This concept is bolstered by a wealth of further measures such as driver training, in which drivers are taught how to recognise danger in plenty of time and avoid risks. They are also shown how to react correctly in the event of an accident. The concept also involves informing passengers of 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.

The Tourismo and Citaro: exemplary safety equipment

The Mercedes-Benz Tourismo touring coach showcasing the very latest safety developments is the perfect example of how this theory is put into practice. The standard equipment includes a wide range of safety-relevant components, a highly effective brake system, powerful headlamps, an ergonomically designed cockpit, exterior mirrors providing outstanding visibility, assistance systems such as the Electronic Stability Program (ESP) with numerous sub-functions, the new Active Brake Assist 4 system as standard and Lane Assist along with many other details besides. A new arrival is the optionally available turning assist system, Sideguard Assist. However, should the Tourismo ever be involved in an accident, the high-strength annular frame structure serves to protect all the occupants and the Front Collision Guard safety system will protect the driver in particular. A fire alarm system for the engine compartment also comes as standard.

The level of safety of the Mercedes-Benz Citaro is just as exemplary. Its cockpit also represents the latest in ergonomic design. As the first low-floor bus in the world, the Electronic Stability Programme (ESP) is provided as an option. The Citaro G articulated bus actually comes with the jack-knife control system Articulation Turntable Controller (ATC) as standard, which has a similar effect to ESP. Preventive Brake Assist comes in as the world’s first active brake assist system for city buses, with Sideguard Assist as the first turning assist system. The Citaro also has a high-strength annular frame structure to protect passengers in the event of an accident and a special crash element to safeguard the driver in a head-on collision. This is standard equipment, as is the fire alarm system for the engine compartment.

Autonomous intelligent cruise control keeps a safe distance

The radar-based autonomous intelligent cruise control feature (AICC) takes the strain off the driver on highways 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. The proximity sensor continuously scans the area ahead of the bus, measuring the distance from and relative speed of the vehicles in front. If there are no vehicles in front, it works like a conventional cruise control system. This system largely relieves the driver of the burden of braking to adjust the vehicle’s speed in medium to heavy traffic on trunk roads and motorways.

The supplementary "stop-and-go" function supports the driver in traffic jams and stop-start traffic. If the vehicle is not stationary for longer than two seconds, the distance control function remains active and moves the coach back up to the pre-set speed. If the vehicle remains stationary for longer than this amount of time, the driver can reactivate the AICC function by gently pressing on the accelerator or on the cruise control button on the steering wheel.

Active Brake Assist: actively helps to prevent rear-end collisions

Active Brake Assist (ABA) actively helps to prevent rear-end collisions and can therefore save lives: Active Brake Assist (ABA) was first introduced in Mercedes-Benz touring coaches in 2008. Continuously developed and enhanced ever since, Active Brake Assist detects an acute risk of a rear-end collision with a stationary or slower-moving vehicle in front and emits a series of warnings before initiating partial and then maximum full-stop braking. Active Brake Assist can actively prevent accidents occurring, or at least reduce the speed of impact and therefore the severity of the consequences of an accident.

Active Brake Assist 4 with pedestrian detection is the result of consistent further development and represents a new milestone. It additionally warns the driver of imminent collisions with moving pedestrians and simultaneously automatically initiates partial braking. It is the first system of its type to perform such functions. This enables the driver to avoid a collision by means of maximum full-stop braking or a steering manoeuvre. ABA 4 will be standard equipment in the high-deck Mercedes-Benz Tourismo from the first quarter of 2019.

Attention Assist: looks out for the driver

Attention Assist is a safety system that constantly monitors information about the condition of the driver using a variety of criteria such as steering movements and activation of the brakes, operation of the turn signal indicator, vehicle speed and the time of day. Attention Assist correlates the data recorded and the adapted driver profile to extrapolate the driver’s reaction speeds and level of fatigue. If a predefined value is exceeded the driver is prompted by the system to take a break.

Brake assist for touring coaches: maximum full-stop braking reduces stopping distance

Brake Assist (BA) is standard equipment in Mercedes-Benz touring coaches. 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 helps to prevent accidents.

Crash impact absorber: protection for the Citaro driver

An outstanding safety feature in the front end of the Citaro city bus is the impact-absorbing collision protection element. Combined with the reinforced A-zero pillars and a defined frame structure which steers impact forces directly to the substructure in a collision, the new Citaro even conforms to the swing-bob impact test for touring coaches as specified in the European regulation ECE R 29.

Continuous braking limiter: safe downhill driving at a constant speed

The continuous braking limiter brakes the touring coach by means of 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.

ESP: significantly reduces the risk of skidding, ATC for articulated buses

The Electronic Stability Program (ESP) was introduced as standard equipment for Mercedes-Benz touring coaches as early as 2003. ESP operates up to the limits of physical possibility to reduce 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.

Mercedes-Benz provided ESP as an option for the Citaro as the first low-floor bus in the world. The counterpart for articulated buses is called Articulation Turntable Controller (ATC). This electronic jackknife control system achieves a similar effect to ESP. It is offered as standard for all Mercedes-Benz articulated buses including the large capacity CapaCity bus.

Front Collision Guard: the passive safety system

Front Collision Guard (FCG) is a unique, complex passive safety system designed to protect the driver and the tour guide at the very front in touring coaches in the event of a frontal impact. Its components include a transverse section which acts as an underride guard for the protection of other road users and can prevent a car, for example, from driving underneath the vehicle, a frame consisting of crash elements which specifically absorb energy in the event of an impact, and a solid frame section for the driver's area including steering, pedals and seat. In the event of a severe head-on collision, this can slide backwards in its entirety and increase the occupants' survival space.

Preventive Brake Assist: the first active brake assist system for city buses

In Preventive Brake Assist, Mercedes‑Benz introduces the first active emergency braking assist system ever for city buses as a world first. The assistance system warns of collisions with moving pedestrians or stationary or moving objects and automatically initiates partial application of the brakes in the event of the immediate risk of a collision. The series of warnings and the braking intervention are configured to the driving conditions expected in urban traffic.

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. The partial braking applied at the same time lasts until the driver intervenes or the bus comes to a halt. The driver can override the intervention at any time by applying the brakes, steering or accelerating. In addition, he or she can warn pedestrians or other road users by sounding the horn siren.

Preventive Brake Assist deliberately does not carry out automatic emergency braking. 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 maximum full-stop braking if required. Preventive Brake Assist is available as an option for the Citaro and CapaCity.

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

Because of the highly complex and rapidly changing traffic situation, turning manoeuvres in urban traffic are among the most awkward tasks a bus or coach driver faces. Cyclists and pedestrians are also sometimes unaware that the bus or coach driver may not be able to see them. Mercedes-Benz therefore offers the Sideguard Assist turning assistance system with pedestrian detection for all versions of the Citaro city bus up to the large capacity CapaCity bus and for the Tourismo high-deck touring coach.

The centrepiece 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 covers the entire length of the bus, complemented by two strips to the front and rear of about two metres each. At speeds over 36 km/h, these zones are extended further.

If there is a moving object in the side monitoring zone, the driver is given a visual warning. In touring coaches, a triangle-shaped LED lights up in the passenger-side exterior mirror. On the Citaro, it is integrated into the A0-pillar on the side of the door. If the sensors detect the danger of a collision, an additional visual warning is also triggered: the LED flashes brightly several times in red. After two seconds, it remains permanently illuminated in red. There is also a vibration in the driver’s seat.

A warning also occurs if the sensors detect a stationary obstacle in the turning curve of the bus. This tracking pattern warning function is effective from 0 to 36 km/h. The other functions of Sideguard Assist are available throughout the entire speed range from 0 to 100 km/h. At speeds above 36 km/h, the new Sideguard Assist also provides the driver with warnings when moving into a right-hand lane. 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. 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 or motorways.

Lane Assist: issues lane departure warnings

Lane Assist (LA) uses a camera system behind the windscreen to detect when there is a risk of the vehicle leaving its lane, continuously monitoring the distance between the vehicle and the marker lines at the edge of the lane. If the vehicle crosses the marker line, the side of the driver's seat concerned starts to vibrate to warn the driver. Lane Assist is activated when the vehicle reaches 70 km/h.