What is the difference between an FOT / Pilot / Naturalistic Driving Study (NDS)?
Field Opeartional Tests (FOT), Pilot projects and Naturalistic Driving studies (NDS) share in common the fact that their main operational phase involves vehicles being driven on public roads in real traffic conditions. Hence, despite being different types of projects they have methodological aspects in common. For that reason, the catalogue in this Wiki also features Pilot projects and Naturalistic Driving Studies.
The following is a brief definition of the three types of projects:
FOT:A Field Operational Test is a study undertaken to evaluate a function, or functions, under normal operating conditions in environments typically encountered by the host vehicle(s) using quasi-experimental methods.
EC officials define Field Operational Tests (FOT) as large-scale testing programmes aiming at a comprehensive assessment of the efficiency, quality, robustness and acceptance of ICT solutions used for smarter, safer and cleaner and more comfortable transport solutions, such as navigation and traffic information, advanced driver assistance - and cooperative systems.
Pilot: According to the European Commission, Pilot projects are pre-deployment projects occuring last in the chain of projects towards deployment.Pilots are not research projects per se but rather they are expected to demonstrate how services can/will be deployed beyond the scope and duration of the pilot project. 
NDS: Naturalistic Driving observation refers to studies undertaken using unobtrusive observation when driving in a natural setting. Both, Naturalistic Driving Studies and Naturalistic FOTs use this type of observation. Naturalistic Driving observation is a new approach among already applied traffic research methods. In Naturalistic Driving Studies (NDS), the driver becomes unaware of the observation as the data collection is organised as discreet as possible and preferably drivers use their own vehicles. The data is used to study the relationship between driver-, vehicle-, and/or environment factors with crash risk.