Final answer:
Rigid pavement is the thinnest highway pavement design.
Step-by-step explanation:
The thinnest highway pavement design for a given loading, soil conditions, and design life would most likely be rigid pavement.
Rigid pavement is characterized by its ability to distribute loads over a wide area, resulting in lower stresses on the subgrade. This allows for thinner pavement designs compared to flexible or semi-rigid pavements.
For example, a rigid pavement design may consist of a relatively thin layer of concrete, which is capable of withstanding heavy traffic loads due to its rigid nature and the ability to distribute these loads effectively.