Test: The new Mercedes-Benz Travego
Stuttgart
Jun 17, 2009
Mercedes-Benz Travego: Illustrious tradition of safety
  • Integral safety concept from the Mercedes-Benz Bus and Coach unit
  • Extensive safety equipment right from the start
  • ESP introduced as standard at an early stage
  • Proximity control maintains a set distance
  • Lane Assistant issues lane departure warnings
  • Continuous Braking Limiter for safe downhill driving at a constant speed
  • New Active Brake Assist actively helps prevent rear-end collisions
  • New: Front Collision Guard passive safety system
Safety and coaches – two words that are inextricably linked. It is a proven fact that the risk of a fatal accident is many times higher when travelling by rail, in the air or in a car. Daimler's research and development activities are geared towards ensuring the highest possible level of safety, whether it be in passenger cars, vans, trucks, buses or coaches. Since its first appearance back in 1999, the Mercedes‑Benz Travego has distinguished itself as an exceptionally safe touring coach. Both its body design - based on extremely robust reinforcements stretching across the roof and down the sides - as well as its dynamic chassis and standard-fit safety equipment have set the benchmark from the very beginning. Now the new-generation Travego - equipped with Active Brake Assist (ABA) and Front Collision Guard (FCG) - has raised the bar once again when it comes to both active and passive safety.
Integral safety concept from the Mercedes-Benz Bus and Coach unit
For the Mercedes-Benz Bus and Coach unit, 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 active­ties across the board in the field of safety. 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 the key aspect of 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.
Travego: exemplary safety right from the start
Since its premiere in 1999, the Mercedes-Benz Travego has earned itself an enviable reputation as a commendably safe touring coach featuring an extensive range of safety equipment. Right from the very start, its standard-equipment package included an electronic braking system (EBS) with internally ventilated disc brakes on all axles, an anti-lock braking system (ABS), acceleration skid control (ASR) and a wear-free retarder as an auxiliary brake. The flawlessly ergonomically designed cockpit with a joystick-style shift lever also set new standards.
In the ensuing years, a whole host of safety components - including the Electronic Stability Program (ESP), proximity control, Lane Assistant, the Conti­nuous Braking Limiter and Brake Assist (BA) - made their debuts in the Travego, allowing it to build on its commanding lead in the safety stakes. All of these deve­lop­ments led to the unveiling of the Safety Coach demonstration vehicle, equipped with all of the relevant safety features available at the time, in 2006. With Active Brake Assist, the Travego has set another milestone in the development of bus and coach safety.
Equally the dynamic yet comfort-oriented suspension and the touring coach's outstanding handling - with each variant boasting a surprisingly small turning circle - set the standards for others to follow from the very beginning. Like all modern Mercedes-Benz buses and coaches, the Travego met the requirements for roll-over resistance in accordance with ECE R 66 before this standard had even come into force. Special equipment available to complement the standard safety package included extremely powerful gas discharge lamps (Litronic headlamps), a reversing camera and exterior mirrors with a "reversing pilot" function.
ESP introduced as standard at an early stage
Daimler was the first bus and coach manufacturer to offer the Electronic Stability Program (ESP) back in April 2002, when it was introduced as special equipment for the Mercedes-Benz Travego. It became standard for all Travego models soon after­wards in October 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.
At the same time, Mercedes-Benz introduced Brake Assist (BA), which detects emergency braking situations based on the speed with which the brake pedal is pressed and provides much higher braking power instantaneously in order to shorten the braking distance and, therefore, help to prevent accidents.
2004: A glimpse of the near future
In 2004 Mercedes-Benz unveiled three all-new safety systems as world premieres in a Travego concept vehicle: proximity control (ART), Lane Assistant and the Continuous Braking Limiter.
Proximity control maintains a set distance
Proximity control makes the driver's job easier on motorways and major roads. If the system detects a slower-moving vehicle in front, it brakes the vehicle auto­mati­cally until the safety distance pre-programmed by the driver is achieved and then maintains this distance. To this end, the area in front of the vehicle is scanned at 50-millisecond intervals by a distance sensor which uses three radar beams to measure the distance to and relative speed of the vehicles in front.
Proximity control can measure the relative speed to an accuracy of 0.7 km/h. If there are no vehicles in front, it works like a conventional cruise control system. In the main, proximity control assists the driver in medium to heavy traffic on major roads, taking control of the vast majority of adaptive-braking tasks, although deceleration is limited to around 20 percent of the maximum braking power.
The distance to the vehicle in front set by the proximity control depends on the vehicle speed and can be indicated as a percentage of the speed shown on the speedo­meter. The proximity control default distance setting can be around 60 per­cent of the speed indicated on the speedometer, although the driver can increase or reduce this distance by defined amounts, as and when required.
At the heart of the proximity control system is a distance radar mounted in the centre of the vehicle, which switches continuously between three radar beams that are emitted by the system. These are arranged so as to ensure that the lanes on the left, on the right and in the centre are monitored (with one beam covering the left-hand side of the vehicle, one the right-hand side of the vehicle and one the centre area directly in front of the vehicle).
Lane Assistant issues lane departure warnings
The Lane Assistant 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 by the width of a tyre, the side of the driver's seat concerned starts to vibrate to warn the driver. The Lane Assistant is not activated until the vehicle exceeds a speed of 70 km/h and is deactivated when the driver indicates, for example to signal an intention to change lanes.
Continuous Braking Limiter for safe downhill driving at a constant speed
The third new system to be introduced in 2004 was the Continuous Braking Limiter, which brakes the vehicle by means of the retarder when the statutory down­hill speed limit of 100 km/h is exceeded. It is therefore practically impossible to exceed the speed limit inadvertently when driving downhill.
In just a short time, the "Travego concept study" was phased into production - when Mercedes‑Benz introduced the Continuous Braking Limiter as standard for the Travego in 2005. Proximity control soon became available as special equip­ment, while the third safety system - Lane Assistant - has been available as an option since 2006.
Safety Coach of the Year 2006
All of these developments led to the unveiling of the Safety Coach demonstration vehicle, based on the Travego, in 2006. The world's safest touring coach, as the experts put it, combined all of the key safety technologies available at the time. Yet development of safety systems continued unabated at Mercedes-Benz - culmi­nating in further pioneering innovations for the new-generation Travego in the summer of 2008.
World premiere: new Active Brake Assist actively helps prevent rear-end collisions
Active Brake Assist (ABA) has won several awards and, more importantly, actively helps prevent rear-end collisions and, therefore, can save lives. Since it was launched in the Mercedes-Benz Actros heavy-duty truck in 2006, it has proven a resounding success, having clocked up a combined total of more than 350 million kilometres on the road. Now it is set to celebrate its world premiere in the bus and coach sector - in the new-generation Mercedes-Benz Travego. If Active Brake Assist detects an acute risk of a rear-end collision with a slower-moving vehicle in front, it emits a series of warnings before initiating emergency braking.
Active Brake Assist is based on the proximity control (ART) system, which has been available as an option for the Mercedes-Benz Travego for several years. It uses the proximity control radar sensor which, in turn, is able to detect obstacles moving within a defined range in front of the vehicle by means of its three radar beams. The distance to and the relative speed of the vehicle in front are monitored and assessed on a permanent basis.
If the traffic situation remains unchanged and there is a risk of a collision, a progressive series of warnings comes into play. Firstly the driver receives a visual warning in the shape of an illuminated red triangle with the outline of a vehicle on the instrument panel along with an audible alarm signal that gradually becomes louder. If the risk of a collision becomes more acute and the driver has still failed to react, partial braking is initiated. The technology used in this instance takes account of the occupants on board by increasing the braking pressure smoothly. If the driver still fails to respond, the system finally applies the full braking power of its own accord.
To warn the traffic behind, the brake lights are switched on fully during partial braking or start to flash during emergency braking. If the vehicle comes to a halt following emergency braking, the hazard warning lights come on automatically.
Reduction in collision speed and accident severity
Although Active Brake Assist cannot always prevent accidents, the application of the brakes can at least significantly reduce the collision speed and, therefore, the severity of the accident.
The system uses a series of progressive warnings to alert the driver in advance, allowing the driver to then manoeuvre the vehicle or apply the brakes in order to avoid a collision. Even though rear-end accidents involving buses and coaches are a rare occurrence, they are among the most serious of accident types. The developers expect Active Brake Assist to bring about a reduction in the number of these accidents involving fatalities or serious injuries. Active Brake Assist for buses and coaches sees Mercedes-Benz taking a further step towards realising its vision of accident-free driving.
New: Front Collision Guard passive safety system
The same applies to numerous other innovations that feature in the new-generation Travego. Front Collision Guard (FCG) is a unique, complex passive safety system designed to protect the driver and tour guide 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. The frame behind this section consists of crash elements which absorb energy in a predetermined manner in the event of an impact.
In addition, the driver's area in the Travego - including the steering, pedals and seat - is now mounted on a solid frame section that can slide backwards in its entire­ty in the event of a serious frontal impact and, therefore, increase the survival space by several crucial centimetres. As well as testing the effect of the Front Collision Guard system using computer simulations, the developers have also put it through its paces in several crash tests under real-life conditions. FCG also complies with future statutory standards for bus and coach pendulum impact tests.
Together with Active Brake Assist, which can reduce the collision speed dramati­cally in the event of an unavoidable frontal collision, FCG provides the driver and tour guide with an unparalleled high standard of safety.
Mercedes-Benz buses and coaches: illustrious tradition of safety
These developments for the Travego mark the continuation of a long and illustrious tradition. In the early 1980s, the strength of Mercedes-Benz bus and coach bodies was demonstrated in initial roll-over tests. By 1981 Mercedes-Benz had already introduced the anti-lock braking system (ABS), followed four years later by the first automated transmission and, in 1986, by acceleration skid control (ASR). Further advances came in 1997 with the introduction of the electronic braking system (EBS) and CAN databus networking for buses and coaches. EBS reduces the brake response time and now enables ideal distribution of the braking force. At the same time, the pedal feel was brought on a par with passenger-car levels for the first time, making the brakes far more responsive to driver input. EBS is also a prerequisite for the electronic safety systems which premiered shortly after the introduction of the Mercedes-Benz Travego.
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