The highest possible degree of safety is something that lies at the heart of the Mercedes-Benz brand. That’s why the brand with the star 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 alphabet of safety and assistance systems covers the gamut of technologies from Attention Assist to Sideguard Assist:
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.
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
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
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.
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.
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.
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.
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.
Mercedes-Benz 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.