There are many ways in which speed can be considered in automotive design. The first and the most obvious one that comes to mind, especially when dealing with brands that have strong racing connotations like Alfa Romeo, is the contribution that design brings to the car's final performance.
Photos courtesy of Automobilismo Storico - Centro Documentazione Alfa Romeo
Every aspect of the future car's design, intended in the most complete way, from the initial design brief to the commercial launch of the model, has a strong influence on its final performance. The most important decisions, that are almost impossible to change later, involve the general layout of the car. The overall dimensions are set at the very beginning, they result from the car's market class and hence the number of occupants and luggage compartment volume. The mechanical components like engine, drive train, suspensions etc. are placed following the maker's engineering tradition. So it is the careful disposition of given elements that makes the difference.
At Alfa Romeo efficiency has always been the most important goal.
Alfa has never made big cars with big engines to achieve high performance, just the opposite, every car had to be just big enough to carry the required occupants and their luggage. Just. Not more. It is easy to understand that this design philosophy was strictly related to Alfa's racing activities that have always accompanied it through the history, there is no place for superfluous on a racing car. Consequently, every new car had to be as compact as possible as that would result in limited weight and cross section.
The weight conditions the acceleration and braking times and cross section, multiplied by the aerodynamic coefficient of the form, influences the maximum speed. Both factors condition the fuel consumption. But it's not as simple as that. When considering weight, it is not only the total number that matters but also the distribution of weight within the car's volume, because it greatly influences car's handling and road holding. The heaviest components need to be placed as low as possible to keep the center of gravity low, but also should be well distributed to achieve good weight balance between front and rear axles. Furthermore, the weight should ideally be concentrated as close as possible around the center of gravity to reduce the polar momentum of the car. And it is not finished yet. There are fixed elements of a car which weight and position never change and there are variable elements, most importantly the occupants, not only their number changes from the driver only to the maximum number for which the car is designed, but also the weight of every occupant may vary considerably. Then there is the luggage that may vary from zero to maximum capacity and the fuel tank, from full to reserve. Also here the variable weight elements should ideally be located as close as possible to the center of gravity to affect as little as possible the weight distribution between fully loaded and just the driver on board conditions.
Also in case of the aerodynamic drag it just isn't enough to achieve the smallest cross section and the best Cx coefficient which influence “only” the maximum speed.
The high speed without stability and safety are highly dangerous and hence unacceptable in any car, let alone in one that is intended to be driven fast often and in full control. Aspects as aerodynamic lift and its distribution between front and rear are of extreme importance if the full adhesion to the ground is to be guaranteed at high speeds.
That is why a negative lift or down-force, appropriately balanced between front and rear, are necessary to achieve, even, and almost always, at the cost of losing some Cx efficiency and consequently the maximum speed. These considerations help to understand the difference between cars “designed” to obtain best “on-paper” performance values as quoted in standard road-tests and which are often downright dangerous when driven fast in real-world conditions, and well-designed and balanced cars that are safe at all speeds in all circumstances.
Again, something that you learn best in racing.
Variable ambient factors such as lateral wind should also be considered to keep under control the sensibility and reaction of the car to that phenomenon. In rainy conditions the road dirt should be kept away from windows and windshield wipers efficiency should be retained also at high speeds.
Another fundamental aspect of car design is ergonomics. It's about fitting different size human beings inside the car, offering them enough space to comfortably sustain even longest journeys. But it is how you do it that makes the difference. First of all, Alfas have always been driver's cars. From the family four door sedan, through two door coupes to the spiders, the same basic ergonomic design principles were adopted. Always starting from the most important (and always present) occupant: the driver. First of all the best possible control of the car must be guaranteed. And that's intended through all the senses.
In an Alfa you are never isolated from the car but on the contrary, it should feel like the virtual extension of your body, you should be able to impart directly your commands and receive the equally direct feed back, without filters.
The steering wheel, the pedals, the gear lever and the “seat of your pants” should not be the mere areas of contact with the car but the very points of extension of your nervous and muscular systems. Just the opposite of the sensory-deprivation, drive-by-wire isolated experience that more and more today's cars are offering the “driver” (?). A gradual introduction to the driver-less cars?
Another aspect of ergonomics and undoubtedly the most important one of sensory control of the car is the visibility. The upper and lower limiting angles of forward visibility and the sideways visibility angles and amount of obscured angles, together with the optical quality of the windshield and the area swept by the wipers in rainy conditions are of utter importance for keeping the car under full control at any speed and in any weather condition. You learn that best when you drive fast on the mountain switch-backs. At night. When it's raining. These are just the basic requirements of car design to be strictly observed if you want to build a serious fast car (and notice we didn't even mention the engine!).
At Alfa they have always been a natural and indispensable part of every new car development. It is quite obvious that all these notions come directly from the long and rich experience in motor racing.
There is no doubt that if you follow the same rules that you apply to your successful racing cars in all your production cars, they will be safe at any speed.
You were probably expecting to hear from a car-designer the importance of how the reflexes flow on the shiny surfaces, or about the Speed-Forms inspired by nature's beauty observed in fauna and flora examples as the origin of the new car's shape... Or, hopefully, the secrets of how to make the car appear fast even when it's standing still?
Or, maybe you wanted to know how we strive to make the new cars more environmentally sustainable? I'm sorry if I deluded your expectations but you will find all those things explained elsewhere much better than I ever could...
At Centro Stile Alfa Romeo we used to approach design in a quite pragmatic way, we used to call it Bellezza Necessaria or Necessary Beauty.