This study examines the consequences of being approved as a Traffic Safe Municipality for municipal traffic safety culture, based on surveys (n = 2255) and interviews (n = 17) in 24 municipalities. Traffic Safe Municipality is an approval scheme for Norwegian municipalities, which defines criteria for systematic traffic safety work. Development of a positive municipal traffic safety culture is an explicit aim of the approval scheme. The respondents in the survey state positive consequences for the traffic safety culture in their own workplace after being approved as a Traffic Safe Municipality. The self-reported focus on traffic safety has increased among immediate managers and among colleagues, and it has become easier to address issues related to traffic safety in one's own workplace. In multivariate statistical analyses, we see that these changes are also linked to the respondents stating that they think more about traffic safety in their everyday work and they state that they behave safer in traffic during working hours. The study has also mapped factors that promote or impede implementation of Traffic Safe Municipality. Lack of resources in the municipality, time pressure, high workload and replacement of personnel may hamper implementation, while top managers' involvement throughout the implementation period is one of the most important prerequisites for successful implementation. We conclude that Traffic Safe Municipality can be interpreted as a measure to establish a traffic safety culture through the implementation of a safety management system in the municipality. Such systems are required as a measure to create a positive safety culture in a number of different high-risk sectors (aviation, nuclear power, oil, and gas). Our study is unique, since we apply this perspective in the municipal sector.