High level of safety for the driver and all other road users: Numerous assistance systems and items of technical equipment in the eActros ensure a high level of safety

Jun 30, 2021
Stuttgart
  • Special crash elements with an aluminium profile can protect the batteries in the event of a side-on crash, while sensors integrated in these can automatically initiate the shutoff of the high-voltage battery.
  • As the eActros drives mostly noiselessly, the standard Acoustic Vehicle Alerting System with warning noises ensures, for example, that pedestrians and cyclists can hear the electric truck better.
  • For greater safety when turning off to the nearside, as well as when driving in the longitudinal direction, the eActros is equipped as standard with Sideguard Assist S1R and the fifth-generation Active Brake Assist emergency braking system.

The latest Actros generation equipped with a conventional diesel drivetrain enabled Mercedes-Benz Trucks to impressively demonstrate the level of safety which is possible to bring to our roads today already as well as how the manufacturer is pursuing its vision of accident-free driving. For the eActros, Mercedes-Benz Trucks didn't just focus on active safety, but also on the challenges which electric vehicles and high-voltage systems bring with them.

Automatic or manual deactivation of the HV system

As a general rule, the eActros batteries, HV lines and other HV components are designed and secured in such a way that, in the event of an accident, not only the high safety requirements of Mercedes-Benz Trucks are fulfilled, but also the legal and regulatory provisions. The Battery Temperature Warning System integrated in the electric truck continually monitors the temperature of the HV batteries. When the temperature is too high, the alarm system in the cab emits a warning tone. The alarm also works when the vehicle is switched off. From a construction point of view, the batteries are protected in a side-on crash by special crash elements fitted to the frame. The aluminium profile of these elements enables as much energy as possible to be absorbed. Integrated in them are also sensors which can detect a crash situation. In such a case, the HV battery would be automatically isolated from the rest of the vehicle. For emergency service crews, there are additional isolation points located under the seats, with which the HV system can be deactivated.

When switched off, the system ensures within just a few seconds that there is no residual voltage in the HV system (outside of the battery), which would otherwise pose a risk of injury. Besides automatic deactivation, if the driver detects a danger, he/she also always has the possibility to manually actuate the HV shutoff installed in the cab. When the HV system is deactivated, the drive system and continuous brake function no longer work. If the low-voltage system (24 V) remains activated, the service brakes, lighting, hazard warning lights and steering continue to work.

Acoustic warning system improves perception of the eActros

As with all electric vehicles, the eActros is also mostly noiseless in operation. In some cases, this may lead to dangerous situations, for example if pedestrians or cyclists only notice the electric truck too late. In order to avoid such dangerous situations, the eActros is equipped as standard with an external Acoustic Vehicle Alerting System (AVAS).

The acoustic warning system in the eActros comprises two speakers – one at the front and one at the rear of the vehicle. They are connected with one another and with the vehicle. Depending on the driving conditions, sounds for driving forwards and reversing are played. The forwards noise simulates a quiet fan noise, while in reverse, an intermittent two-tone sound is emitted.

The AVAS more than fulfils the sound levels stated in UNECE Regulation 138.01 for forwards travel by at least 10 dB and for reversing by at least 15 dB. In this way, good perception of the eActros has been assured. The legally permitted maximum level is, however, not exceeded and subjectively, drivers or passers-by are not disrupted by the sounds. Furthermore, an additional safety feature has been implemented which goes above and beyond the stipulations of UNECE Regulation 138.01: as soon as the driver engages transmission position "D" and releases the parking brake, the noise for forwards travel is played in order to allow better perception of the vehicle's presence. If the driver shifts to transmission position "R", the reversing sound is emitted.

Greater safety when turning off to the nearside

The improved perception of an electric truck plays a central role when turning off to the nearside. Accidents in this area are among the worst type of inner-city accident possible, particularly for unprotected road users such as cyclists and pedestrians, but also for the truck drivers themselves. In order to avoid such accidents as far as possible or to at least reduce their consequences, the eActros is equipped as standard with Sideguard Assist S1R. If there is a risk of a truck driver unexpectedly overlooking a cyclist or pedestrian in their blind spot when turning off to the right, the system can assist the driver with a multi-stage warning process. For its visual warning messages, S1R uses the MirrorCam display which is also installed on the eActros in place of regular main and wide-angle mirrors.

The core of the Sideguard Assist is made up of two short-range radar sensors on the frame on the co-driver's side in front of the truck's rear axle. The system is designed so as to monitor the entire length of the vehicle combination plus two metres to the front, one metre to the rear and up to 3.75 metres to the nearside. Sideguard Assist S1R does not actively intervene in the brake system, however. Assisted by the system's warnings, the driver is responsible for duly braking the vehicle.

Active Brake Assist 5 with pedestrian detection

For years, a large proportion of accidents involving heavy-duty freight vehicles have occurred when travelling in the longitudinal direction: accidents in which a truck collides with a preceding or stationary vehicle due to driver distraction, too short a distance to the vehicle in front or failure to adjust the vehicle speed, for example. With the fifth-generation Active Brake Assist (ABA) installed as standard in the eActros, accidents like this can generally be avoided. ABA 5 works using a combined radar and camera system. Upon detecting the danger of an accident with a preceding vehicle, a stationary obstacle or a person – be that crossing in front of the vehicle, walking towards the vehicle, in the vehicle's lane or suddenly coming to a halt when startled – the system first warns the driver visually and acoustically. If the driver fails to react sufficiently, in the second stage, the system initiates a partial application of the brakes with deceleration of up to three metres per second. This corresponds to roughly 50 percent of the maximum braking performance. If the risk of a collision persists, ABA 5 initiates a full application of the brakes – in the case of moving pedestrians, this applies up to a vehicle speed of 50 km/h. Finally, to come to a stop the vehicle applies the new electronic parking brake.

With all assistance systems, Mercedes-Benz Trucks aims to support the driver as much as possible within the respective limits of each system. However, as the law prescribes, the driver remains fully responsible for driving the vehicle safely at all times.

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