(Source: http://babelturbo.blogspot.com/)

Petersburg scientists designed a new kind of rear-view mirror: it now combines spherical and aspherical mirror elements. 
A rear-view mirror is one of the vital car parts that ensure a vehicle's safety on the road. In this respect the actual positioning and angling of the mirror are important. Yet the scope of what the driver can see in the mirror also matters: the more he can see in the rear-view mirror, the more correct will be judgement on the road. 
A Polytech research company from Saint Petersburg designed a new mirror that combines spherical and aspherical elements, significantly increasing the view. The mirror consists of two zones. The one closer to the driver is a regular spherical mirror. The scope of what is reflected here cannot be less than required by standards. 
 Another zone, a convex surface farthest from the driver, is mathematically calculated and curved according to a special law (with a gradual increase in the curvature near the edge of the mirror). It is this aspherical zone that substantially increases the space sector.
The aspherical mirror gives the driver full control over the traffic situation. The driver can at all time see most of the road and cars behind. This effect is due to a substantial expansion of the adjacent zones of reflection mirrors (spherical and aspherical), which is obtained by increasing the angle of driver's view - up to 40 ° (instead of the standard  13 ° in other car mirrors).
The main advantage of this mirror is that the driver will no longer have the so-called "dead zones", when the car behind disappears from the view for some time, while being in a couple of dozen meters from the driver.
For the convenience of the driver a division between spherical and aspherical mirrors is clearly marked. The design of the curvature of the aspherical mirror is such that, as the object in the rear-view mirror approaches the driver, its reflection gradually shifts from spherical to aspherical zones.
Roadtests indicate that these aspherical mirrors are a good alternative to the usual flat mirrors or only spherical mirrors and really make car driving safer and more comfortable.