For years, Mercedes-Benz has pursued its vision of accident-free driving. The integral safety concept covers all phases of automotive safety — safety when driving and in dangerous situations, protection in the event of an accident and minimising the impact of an accident. Safety is also integrated into the eCitaro city buses as standard. The body itself protects the passengers in the event of side impact. In the event of a rear-end collision, the reinforced front end minimises the impact of an accident while protecting the driver.

eCitaro
Safe driving
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Electronic Stability Program (ESP®).
How ESP® works.
The Electronic Stability Program (ESP®) is an active system for increasing driving safety and stability. It makes a noticeable contribution to reducing the risk of skidding during cornering or evasive manoeuvres. This is achieved by specifically controlling the braking forces on each individual wheel in critical, dynamic driving situations, for example if the bus approaches physical limits when cornering. At the same time, the engine output is reduced. A possible "breaking-out" of the bus is thus prevented by the finely metered braking within the limits of the physical possibilities.
Among other things, ESP® monitors the lateral acceleration of the bus. If, on long bends – such as motorway exits – or with rapid lane changes, the bus reaches a critical driving situation, the vehicle speed is automatically reduced so the bus returns to a situation of driving stability. The ESP® is comparable to that used in passenger cars, but is adapted for use in buses thanks to specific extended features.
Acceleration Skid Control (ASR).
ASR prevents the drive wheels from spinning in two ways. On the one hand, ASR minimises wheel spinning through a measured braking intervention. On the other hand, the torque of the engine is regulated via the "electronic accelerator pedal". Even at full throttle, the engine only provides as much power in critical situations as the drive wheels can transmit – a major advantage for controlled pulling away and driving stability.
When starting off, the torques applied and the wheel speeds of the drive wheels are monitored. In this process, torque distribution is controlled in such a way that spinning is prevented. This ensures that optimum power flow is always guaranteed.
ASR helps the driver to minimise the risk of the drive wheels spinning and consequently of the rear of the vehicle (rear-wheel drive) breaking out laterally when accelerating. Especially for high-torque engines, ASR thus provides increased comfort and enhanced safety when pulling away – particularly on roads with varying grip.
Anti-lock braking system (ABS).
How ABS works: there are sensors fitted on all four wheels which detect the rotational speed of each wheel and pass this information on to a central control unit. If the critical point of blocking the wheels is reached, the wheel is stopped at precisely that threshold by pressure variation. The brake pressure can be increased and decreased numerous times in the space of a second.
When braking, all the forces acting on the wheels and the rolling behaviour are continually monitored. The braking forces acting on the wheels are distributed in such a way that no wheel can lock, and the steerability of the vehicle is preserved as far as possible.
In December 1970, Mercedes-Benz presented the world's first electronically controlled ABS – a revolution in driving and road safety. Thanks to targeted electronic braking intervention, the wheels don't lock for long times. The risk of losing steering stability is minimised and, in the case of a full application of the brakes, the vehicle can be steered in the desired direction. ABS technology forms the basis for further developed electronic safety systems such as the electronic stability program (ESP®) or the brake assistance system (BAS).
Front-Collision-Guard.
A crash element is installed in the extended front end as additional collision protection. Together with a reinforced, defined frame structure, in the event of a collision it conducts impact forces directly into the understructure. This results in better protection for the driver and the driver's footwell area. Specifications based on the pendulum impact test in accordance with ECE R29 are met.
Sideguard Assist.*
The high traffic dynamics in city bus transport make great demands on the driver. The Sideguard Assist assistance system supports the driver primarily when turning towards the left in road traffic by making the driver aware of the presence of other road users and stationary obstacles and by warning if there is a danger of collision.
The system operates in multiple stages: in the first stage, it informs the driver, in the second stage it emits an additional warning.
If a moving object is located in the side monitoring zone, the driver is informed visually. A triangular-shaped yellow LED lamp lights up on the A0 pillar on the co-driver's side. A warning symbol additionally appears on the central display. If the driver initiates or continues an action that could lead to a collision, an additional visual warning is given. The LED lamp flashes first in yellow, then in red. After this the highest level alarm follows: a red flashing lamp accompanied by vibration of the driver's seat.
In addition, Sideguard Assist can perform the task of a lane change assist function; it works with the same warning cascade.
Preventive Brake Assist.*
The Preventive Braking Assist function from Mercedes-Benz is the world's first active Brake Assist System for public city transport buses. This assistance system warns of a possible collision with stationary or moving objects. In case of an acute danger of collision automatically initiates a braking manoeuvre with partial braking. Warning cascade and brake application are precisely designed for use in urban traffic.
In case of an imminent collision, the Preventive Brake Assist function warns the driver both visually, with a red triangle with a vehicle symbol lighting up in the central display, and acoustically. At the same time the system initiates a partial braking manoeuvre. This brake application is held until either the driver intervenes or the bus comes to a stop.
Acoustic Vehicle Alerting System.
The eCitaro also features the Acoustic Vehicle Alerting System, a sound generator which creates an artificial sound effect similar to a combustion engine, at speeds up to 30 km/h. The system increases people's awareness of the quiet, fully electric eCitaro and thus protects pedestrians and cyclists.
The cornering light function.
The cornering light function provides significantly improved safety for night-time driving when turning corners at poorly lit junctions, at roundabouts or when manoeuvring and reversing.
The cornering light function is activated automatically at speeds of up to approx. 40 km/h if the main headlamps are on, the turn signals are actuated or the steering wheel is turned. One of the two front fog lamps is switched on to illuminate the area to the side and front of the vehicle which is not lit by the main headlamps. The intelligent electronic system switches the dimmed cornering lights on or off. This gives the eye a chance to adjust to the changed light situation.
Tyre pressure monitoring (TPM).*
The tyre pressure monitoring system warns of drops in tyre pressure in one or more tyres before and during the journey. It monitors the pressure of all tyres and shows the readings on the multifunction display.
Correctly inflated tyres last longer and above all enhance safety when driving. The tyre pressure monitor can help to recognise falling pressure in one or more tyres when driving and avoid potentially serious consequences.
For this purpose, a sensor on the tyre interior measures air pressure and temperature. This data is transmitted by radio at regular intervals to a receiving aerial on the underfloor and forwarded to the control unit. Tyre pressures can also be shown in the multifunction display if required.
Over the course of several months, tyres gradually lose air through diffusion. The tyre pressure monitor displays a message in good time to prompt the driver to correct the pressure. If there is a significant drop in pressure when driving, a yellow warning light comes on and a warning message is displayed, enabling you to take appropriate action.
Monitoring of the passenger compartment.
The video monitoring cameras installed can keep track of the events taking place on the bus. A video monitoring system can not only improve the sense of safety for the bus driver and passengers, it can also record troublemakers who commit acts of vandalism or violence.
The data is transmitted to the monitor in the bus driver's workstation. The bus driver can then better view and evaluate events occurring in the passenger compartment and, if needs be, react in the event of danger.
The vehicle is labelled with pictorgrams to inform passengers that the vehicle is video-monitored. Video monitoring enhances the subjective sense of safety for driver and passengers and thus the appeal of using public transportation. The video monitoring system is an optional extra.
More information on the video monitoring function and data storage is available from our bus sales consultant.
Special Edition eCitaro.
Omnibus magazine - The magazine for bus operators and transport companies.
* Optional equipment