Traffic models that are described by interconnected ordinary differential equations (ODEs). This area includes the design of feedback laws (e.g., Cruise Controllers) to ensure the safe operation of vehicles in both lane-based and lane-free traffic environments.

Traffic models characterized by Partial Differential Equations, which describe the collective behavior of traffic flow (e.g., density and velocity) over space and time. This area involves the derivation of the equations that describe the traffic flow from the derived cruise controllers on a microscopic scale as well as the analysis of traffic flow at the aggregate level.

A control strategy in which the feedback law is updated at discrete time instants, even though the system may be continuous in time. This is common in modern digital control systems, where controllers are implemented using digital computers or microcontrollers that operate on sampled data. 

This is a central problem in control theory and is used to estimate the state of a system when not all states are directly measurable. This is especially important in modern control systems, where sensors may only provide partial information about the full system state, and is widely used for localization—particularly in robotics, autonomous vehicles, and aerospace systems.