On the French national road network, over the past ten years, from one to two road workers are killed and thirty injured during interventions every year. The number of killed and severely injured is the same for drivers. However, it is worrying from a social point of view and it is a priority for road operators in terms of safety at work. In France, several experiments are in progress. For French authorities, it is often difficult to obtain direct measurable impacts of these experiments on both drivers’ and road workers’ safety. In fact, there is no system analysis centred on acceptability. So, it is difficult to adjust or change existing rules and guidelines. Recently, Cerema Normandie-Centre used human sciences and ergonomic approach in two field studies related to work zones' safety. In the context of these two studies, we proposed a conceptual and methodological framework to investigate work zone and workers’ safety. After an analysis of the accidents on the national road network, this framework combined field studies on road workers' practices and on drivers’ perception and understanding of work zones. A special attention throughout the process focused on the safety level of drivers and road workers. In this project, Cerema Normandie-Centre worked in close cooperation with several road operators. The work carried out underlined the importance of a priori validation of both the configuration of the countermeasure and of the acceptability of the beneficiaries (i.e., network managers, road workers and road users). Indeed, the a priori validation ended up in the changing of countermeasure configuration and in the evolution of the carried out of this countermeasure by the workers.