How do decision-makers justify the implementation of 30 km/h interventions in the Netherlands? An analysis of 47 traffic order documents

Background: Lowering speed limits to 30 km/h offers road safety and health benefits, yet the justifications for local decision-makers to implement 30 km/h limits remain unclear. We examined how local decision-makers justify and implement 30 km/h policies in the Netherlands. Additionally, we studied neighbourhood socio-economic status (SES) and urban–rural differences in these justifications and implementations of 30 km/h policies. Methods: Two researchers independently searched traffic order documents from the Official Gazette of the Kingdom of the Netherlands to obtain all annual speed limit implementations in the two largest Dutch cities (Amsterdam and Rotterdam) and four rural municipalities between January 1st 2016-November 1st 2022. We extracted justifications, additional physical measures, and X- and Y-coordinates of affected street segments. An evidence synthesis was provided for the whole sample, separately for low, middle, and high SES neighbourhoods, and urban and rural municipalities. Results: We included 47 documents. The percentage of 30 km/h road length increased from 53.8 % in 2016 to 54.7 % in 2022, equaling 40 km of additional street length with 30 km/h limits. Traffic safety was the most common justification for 30 km/h(59.6 %). Other public health benefits were rare and only included noise exposure and/or livability(12.8 %). Additional physical measures were diverse in nature, with speed bumps (19.1 %) and pedestrian crossings (12.8 %) being most common. In middle neighbourhood SES a relatively high percentage of street length changed to 30 km/h (0.5 %, 2.8 %, 0.7 % for low, middle, and high SES:). Urban municipalities had a slightly larger percentage of street length becoming 30 km/h than rural municipalities (0.6 % and 1.3 %). Safety-related justifications were especially common in low and middle SES neighbourhoods and urban municipalities. Discussion: Safety was the most common justification for 30 km/h. Few documents emphasized other public health benefits. Future research should investigate effects of 30 km/h interventions on public health outcomes and SES inequalities, include rural areas, and examine the role of specific physical measures.