Everything designed to help prevent accidents from happening comes under the heading of active safety. The primary active safety aspects include: Directional stability: this is the result of the chassis's suspension set-up and its cornering stability. Steering precision, braking power and braking stability also have a role to play. Physiological safety: this describes the strain placed on the occupants by vehicle vibrations, noise from the chassis and engine as well as climatic influences. Each of these factors should be minimised to limit the strain on the driver. Perceptual safety: this is improved by a well-designed vehicle lighting layout and by good visibility (all-round view, clear view to the rear with the blind spot kept as small as possible). Operational safety: this is achieved on each and every Volkswagen model thanks to the logical arrangement of all control stalks and switches for e.g. the lights, windscreen wipers, air conditioning and radio. All of these elements must be placed within easy reach in the driver in the most optimum position possible. A high standard of active safety avoids hazardous situations, whether these are unforeseeable situations triggered by external factors beyond the driver's control or situations which the driver is partially responsible for causing by being inattentive, for instance. Many of today convenience features also boost active safety. The rain sensor is one example of this: by relieving the strain on the driver it offers optimum convenience. At the same time, it ensures that the driver has a clear view through the windscreen at all times, thereby boosting active safety. Another example is the automatic air conditioning: by maintaining a pleasant climate inside the vehicle, it improves passenger well-being on the one hand and, on the other, it prevents lapses in concentration. Tests have shown that when the temperature of the vehicle interior is 27 °C, the driver misses six percent more visual and acoustic signals than at 21 °C. Together with the passive safety elements, active safety features help to ensure optimum protection for all occupants of the vehicle.