Perceived legitimacy is important, often more so than deterrence, to explain and improve compliance with legal rules. However, several issues in the definition and measurement of perceived legitimacy have recently been highlighted and in different fields. A previous review of the literature (Varet et al., 2021), carried out on this issue, in the field of road safety, proposed a multidimensional model of the perceived legitimacy of traffic rules. The present study developed and tested theses insights through the validation of a self-report scale: the Traffic Rules Perceived Legitimacy scale. A hierarchical model underlying the scale was hypothesized with two second-order factors (i.e., instrumental factor, normative factor) and four first-order factors (i.e., effectiveness, efficiency, moral alignment, fairness). A pilot study (N = 74) was designed to pre-test a pool of items. The main study (N = 833) was designed to assess the internal and the external validity of the proposed scale, and a quicker single-item measure. The results corroborate the internal validity of the scale and the hypothesized hierarchical model. As expected, hierarchical regression analyses confirmed that the perceived legitimacy of traffic rules was a better predictor of compliance than perceived deterrence, risk of accident, and social norms. The value and limitations of the corroborated model for defining and measuring the perceived legitimacy of other objects, within and beyond the field of road safety, are discussed. Practical implications in the field of road safety field are also discussed.