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Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road irregularities would be judged to have low ride quality. Key factors for ride quality are Whole body vibration and noise.
While pleasant, the comfort of the vehicle driver is also important for car safety, both because of driver fatigue on long journeys in uncomfortable vehicles, and also because road disruption can impact the driver's ability to control the vehicle.  
Automakers often perceive providing an adequate degree of ride quality as a compromise with car handling, because cars with firm suspension offer more roll stiffness, keeping the tires more perpendicular to the road. Similarly, a lower center of gravity is more ideal for handling, but low bodywork forces the driver's and passengers' legs more forward and less down, and low ground clearance limits suspension travel, requiring stiffer springs.
Ride quality is also related to good braking and acceleration on poor surfaces. It protects the car itself, as well as its passengers and cargo, from vibration that might eventually damage or loosen components of the car. 
On the other hand "poor" ride quality improves blood circulation, helps to keep the driver awake, helps the driver sense speed and road condition and is enjoyed by small children and traditional sportscar enthusiasts.
Historically, weight was key to allowing cars such as the Rolls-Royce Silver Cloud and the Cadillac in the 1950s and 1960s to have have more comfortable ride quality. The downside is that weight also contributes to poor fuel efficiency. From simple physics, soft ride is actually caused by the ratio of the weight to the spring stiffness.
In most of the world, the high price of gasoline effectively prevents most motorists from using massively heavy cars.
Over time, technology has shifted this curve outward, so that it is possible to offer vehicles that are extremely comfortable and still handle very well, like the Citroën DS, or vehicles with excellent handling that are also reasonably comfortable, like the Mercedes E-Class or BMW 5-Series. One technical solution for offering both excellent comfort and reduced or eliminating body roll is by using computer controlled suspensions, such as hydraulic active suspension system (like Active Body Control) or active anti-roll bars, however such systems are expensive because of their complexity.
Impacts on ride quality
Load bearing also interferes with ride quality - the suspension settings are very stiff so the vehicle doesn't change pitch when loaded - most trucks thus do not ride particularly comfortably. In passenger vehicles, self-leveling suspension has been introduced to counteract this effect.
Road construction quality and maintenance have a direct impact on ride quality in vehicles. In jurisdictions where all roads are relatively smooth, the passengers are undisturbed already and the vehicle can be optimized for a higher degree of handling. In most industrialized countries, as well as in many development countries, pavement condition is scanned on road network level using laser/inertial road Profilometers. The Profilometer records road geometry and condition while driving at highway speed. Results from Profilometry can be used to design an optimal geometric pavement repair, eliminating all long wave unevenness, roughness, erroneous cross slope magnitudes and undesired cross slope variance, with the least road grinding and paving efforts. The outcome is a surface with superior ride quality.
- International standard ISO 2631-1 (1997) Mechanical vibration and shock—Evaluation of human exposure to whole-body vibration—Part 1: General requirements.