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Safety definitions - the passive and the active

No-one wants to contemplate an automobile accident, but if it's a risk (and it is) then we want the best technologies available to either avoid it altogether or - if it happens - reduce the worst of the impact consequences for the people involved.

No-one wants to contemplate an automobile accident, but if it's a risk (and it is) then we want the best technologies available to either avoid it altogether or - if it happens - reduce the worst of the impact consequences for the people involved. Active safety systems are designed to prevent the accident happening in the first place - the driver assistance systems that can warn the driver or actively intervene in a situation to help the driver to avert a collision.

In simple terms, passive safety is designed to mitigate the impact effects of collision - it won't stop the accident happening but it will reduce the severity of injuries to vehicle occupants. Seatbelts and airbags are the most obvious examples of passive safety equipment and a seatbelt for every seat and airbags for the front seat occupants are the norm these days. 

Automotive supplier and passive safety specialist Autoliv classifies passive safety for injury mitigation into three stages, each with a suit of technologies to help mitigate injuries:  


  • Early sensing 

  • Active seatbelts 

  • Active structure 

  • Active knee bolster 


  • Pedestrian protection 

  • Adaptive seatbelts 

  • Adaptive airbags 

  • Anti-whiplash 


  • Black box function (event data recorder) 

Active Safety: Driver assistance systems 

The European Commission (EC) defines driver assistance systems as those which help drivers to avoid or mitigate an accident through sensing the nature and significance of the danger. The EC says that, depending on the significance and timing of the threat, these onboard systems will: 

  • alert the driver as early as possible to an impending danger; 

  • warn him or her if there is no driver reaction to the first alert; 

  • actively assist or ultimately intervene in order to avert the accident or mitigate its consequences. 

According to BMW, driver assistance systems “are vehicle functions which help the driver to take in information and make the right decisions, and relieve him of awkward driving tasks. In the future, the targeted provision of information will make it even easier for the driver to make the right decisions quickly. The result is assured responses at the wheel, even in computer road simulations.” 

Driver assistance systems – either on the road or still on the drawing board – divide into three distinct categories: 

  • Collision-warning systems – this is the original term for forward and side radar systems which alert the driver but does not control the engine speed. Driver support systems without active intervention can be viewed as a pre-stage to vehicle guidance. They only warn the driver or suggest a driving manoeuvre. 

  • Collision-mitigation systems – in addition to sending out a warning to the driver (either through audio, visual or vibrating the steering wheel), these systems aim to assess the danger ahead and activate various active safety features, such as pre-tensioning the seatbelts. 

  • Collision-avoidance systems – using these systems mean that some degree of control is taken over from the driver if he doesn’t react in time to avoid a crash. There are some technologies available today that fit inside this group. 

All of these driver assistance systems – from collision warning through to avoidance technologies – are feasible either now or at some point through this decade. However, there are significant problems in software control, not least how to make the various systems work together to form a true protection zone around the vehicle and then develop algorithms to determine if or when the system should intervene with the driving process. 

As far as 2020 is concerned much depends on prospects for the economy and measures that Beijing may introduce to stimulate demand.

Electronic braking systems

If a driver wants to come to a halt as quickly as possible, he or she steps on the brake pedal quickly but often not firmly enough and therefore wastes braking distance. A brake assist system provides support here. During emergency braking, it builds up the maximum braking force within fractions of a second so that the vehicle stops sooner. According to the European Union’s Commission (EC), if all vehicles were equipped with these kinds of systems, up to 1,100 fatal accidents involving pedestrians could be avoided in the EU every year. The EC, therefore, recommended mandating the installation of brake assist systems in all passenger cars registered in the EU from October 2009. If a vehicle is equipped with the electronic stability programme (ESP), the brake assist does not require any additional components. Emergency braking is detected through the fast actuation of the brake. For vehicles without ESP, some manufacturers offer a mechanical solution in the brake booster. If the speed at which the brake pedal is pressed exceeds a certain value, an inertial-controlled valve opens immediately, allowing ambient air to enter the working chamber of the brake booster. This instantly boosts the braking force until the ABS kicks in. If the driver lifts his or her foot from the brake pedal, the additional boost is immediately cancelled again.

Although electronic stability control (ESC) is a generic term, some automakers use a variety of different trade names for ESC such as Vehicle Stability Assist (used by Acura), Vehicle Dynamic Control (Alfa Romeo) and Dynamic Stability Control (BMW). The most common term, however, is ESP (Electronic Stability Programme). 

Bosch provides a useful definition of electronic braking systems.  The German supplier states: “The electronic stability programme includes the features of both the ABS anti-lock braking system and the TCS traction control system. ABS stops the wheels from locking when the brakes are applied, and TCS helps to prevent the wheels from spinning when the car starts to drive. ESP, in addition, detects imminent skidding, using sensor signals to compare the direction in which the driver wants the vehicle to move and the direction in which the vehicle is actually moving. If the two do not match, the system intervenes. By reducing engine speed and applying braking pressure at individual wheels, it helps prevent skidding and keeps the vehicle safely on track within the laws of physics. ESP is also a central component of future safety systems. Together with sensors that monitor the vehicle's surroundings, for example, it can detect critical situations early on. In 2009, the Bosch predictive emergency braking system (PEBS) went into series production as an optional feature in the Audi A8. If PEBS detects the danger of a rear-end collision, it warns the driver and helps him brake to avoid the collision. If the collision cannot be prevented, it automatically triggers full braking shortly before impact, making the accident considerably less severe." 

Passive safety: Frontal airbags

Airbags are designed and constructed to protect drivers and passengers in case of an accident.  Airbags cannot be replaced by other passenger occupant safety systems like seatbelts but rather provide additional occupant protection. 

According to Autoliv, airbags are among the most important automotive safety products, since the concept of inflating a textile cushion could be used in both frontal impacts and side impact collisions to protect a great variety of body parts. In frontal impacts, says Autoliv, driver airbags are estimated to reduce fatalities by 25% for belted drivers and serious head injuries by over 60%. For front-seat passengers (that are further away from the instrument panel than a driver from a steering wheel) the protective effect is estimated to be 20%. 

Meanwhile, side impacts curtain airbags are estimated to reduce the risk for life-threatening head injuries when occupants are sitting on the side of the vehicle that is struck, while thorax airbags reduce serious injuries to the chest by approximately 25% in side-impact collisions. 

There is also an increasing demand for knee airbags and anti-sliding airbags, because frontal airbags and modern seatbelts have reduced the risk for head injuries but not the injuries to the legs. More specifically, anti-sliding airbags may be installed in the rear seat cushion of a vehicle. In a crash, the airbag raises the front-end of the seat cushion to prevent the occupant from sliding under the seatbelt. This reduces the risk for knee, thigh and hip injuries for belted occupants. For example, the VW Golf Mark VII comes equipped with no less than seven airbags, including a driver's knee bag. 

Consequently, Autoliv points to a growing focus on using airbags to also prevent long-term disabling leg injuries. “It is important that people not only survive crashes but also are able to walk, and lead a normal life,” says Autoliv. 

In terms of the number of airbags installed in a vehicle, it depends on the make and model.  In addition to the airbag for the driver and front passenger, some vehicles include airbags installed on both sides of the front seats and both sides of the rear seats to protect occupants in the event of a side collision as well as curtain airbags for protecting against head injury. In addition, there are airbags for protecting passengers’ knees and lower limbs. Today, some vehicles are equipped with ten or more airbags. 

Side-impact airbags

There are a number of vehicles equipped with side airbags. While there are several types of side airbags, all are designed to reduce the risk of injury in moderate to severe side-impact crashes. These airbags are typically located on the outboard edge of the seat back, in the door or in the roof rail above the door.

Seat and door-mounted airbags all provide upper body protection. Some also extend upwards to provide head protection. Two types of side airbags, known as inflatable tubular structures and inflatable curtains, are specifically designed to reduce the risk of head injury and/or help keep the head and upper body inside the vehicle. While side airbags are smaller than front airbags, they must deploy very rapidly.

According to Autoliv, side-impact collisions account for a quarter of all injuries to car occupants, but they account for more than one-third of the serious and fatal injuries. One major reason is that the side of the vehicle is a thin crumple zone and the space between the occupant and the side of the vehicle is small.

According to data from real crashes in the US, side airbags that include head protection are reducing deaths by about 45% among drivers of passenger cars struck on the near side, i.e. the side closest to the occupant. This study from the Insurance Institute of Highway Safety also found that "the highest effectiveness (74% risk reduction) is in two-vehicle crashes when a car with head-protecting side airbags is struck by another car or minivan. Mortality reductions also were substantial when the striking vehicles were pickups or SUVs, suggesting that head-protecting side airbags are addressing some of the problems of incompatibility when passengers’ cars are struck in the side by vehicles with higher ride heights". 


Autoliv notes that seatbelts are estimated to reduce the overall risk for serious injuries in crashes by 60-70% and the risk for fatalities by about 45%. In non-collisions, mainly rollovers, the reduction in fatalities is about 75%.

To further reduce the risks, especially if the seatbelt is not correctly positioned. Autoliv has developed seatbelt pretensioners, load limiters, active seatbelts and other innovations.

According to Autoliv, retractor and buckle pretensioners tighten the belt at the onset of a frontal crash, using a small pyrotechnic charge.  Slack is eliminated and the occupant is restrained as early as possible, thereby reducing the risk of rib fractures.

In an accident, says Autoliv, load limiters release some webbing in a controlled way to avoid the load on the occupant’s chest from becoming too high.

Lap pretensioners further tighten the webbing to avoid sliding under the belt which improves lower leg protection and prevents abdominal injuries from a loose belt.

Autoliv's Active Seatbelt has a pre-pretensioner that gives a gentler load on the occupant’s chest in the event of a crash. A high-speed electrical motor tightens the seat belt as early as one-tenth of a second before a likely crash, using the vehicles electronic stability sensor, a panic-braking sensor, or a pre-crash radar to start the belt-tightening

Autoliv started to produce two-point static seatbelts as early as 1956 and was three years later first in the world with 3-point belts, to Volvo. Autoliv also pioneered the 3-point retractor belt in 1967 and the seatbelt pretensioner in 1986. 

Larger, curved screens

Jump into a new car today and you are almost sure to find a tablet-style touchscreen infotainment system positioned centre stage of the dash. It acknowledges that most of us no longer use maps to find our way around but expect the car to guide us to our destination and remain connected throughout the journey. For example, the Volvo XC90 comes loaded with semi-autonomous and connected car features, most of which are displayed on an intuitive centre console touchscreen.

As with most new technologies, what starts in the luxury market often trickles down the car segments. Inside the new Honda Civic, positioned at the top of the piano-black finish centre console - and drawing the eye as the push start is pressed - is a Honda Connect 2 seven-inch touchscreen, serving as the main point of contact to control the infotainment and climate control functions. This second-generation of Honda’s infotainment and connectivity system incorporates Apple CarPlay and Android Auto integration.

Tomorrow’s cockpits, according to Harman, will have more curved screens designed using OLED technology. The main advantage of an OLED display is that it works without a backlight, enabling it to blend into the interior.

Screens are becoming larger, too. The Tesla Model S features a huge 17-inch screen. But that is just the tip of the iceberg. China’s Byton has debuted its first concept car. A notable feature of the electric SUV is a colossal 49-inch screen stretching the width of the dash.

Whether or not such high-tech wizardry will actually make it onto the road, the above concepts demonstrate the direction the auto industry is taking.

Voice recognition

While giving instructions in our cars is nothing new, putting questions to the likes of Alexa and Cortana while on the road is. Automakers are fast adopting virtual assistants, confirming that speech is becoming the preferred interface for tomorrow’s cockpit.

Voice recognition is seen by some as the answer to eliminate many controls that have traditionally been manually operated. Voice can play an important part of a multimodal HMI solution for inputting information or for cutting through layers on the menus by requesting a function directly. Traditional voice control was centred on a set of fixed commands with catatonic responses which required some level of driver training prior to operation of the system. With the advent of the new low power, high performance microprocessors, smarter voice command engines linked into the HMI logic are now available. Even natural language and grammatical analysis are becoming more achievable.

Voice recognition, although already an option, looks set to play a bigger role as cars gradually become more autonomous.

If in doubt, ask: Microsoft’s Cortana AI system forms part of BMW’s Connected Car vision.

Gesture recognition

Looking down at a touchscreen (without haptic feedback) can be distracting. Gesture recognition is therefore said to be the Next Big Thing, regarded as the logical next step from touchscreens and buttons. Gesture control operates via a stereo camera within the cabin that can recognise certain hand movements for pre-programmed adjustments and functions. Rotating your finger clockwise at a screen could turn up the volume or a finger gesture could answer or decline a call. While such novelties will make life simpler for the driver, it should also simplify interior design and liberate space for storage options.

Interior lighting trends

Advances have also been made in the interior lighting department. Not so long ago, interior lighting consisted of central and side headliner lights, complemented by low-level ambient lighting located mainly in the cockpit area. Today, the accent has changed, thanks to widespread use of LEDs enabling personalisation of car interiors. For example, during night time driving, the Mercedes-Benz E-Class takes on an entirely different feel thanks to the ambient interior LED lighting that can be personalised using a palette of no fewer than 64 colours. It really does start to feel like a cockpit, adding illuminating highlights to the trim, the central display, the front stowage compartment on the centre console, handle recesses, door pockets, front and rear footwells, overhead control panel and mirror triangle.

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