Background Traffic-related crashes are a growing cause of premature death and disability, particularly LMICs. The Bloomberg Philanthropies Initiative for Global Road Safety (BIGRS) is a multi-country technical assistance (TA) program aiming to reduce traffic-related injury and mortality.

Objective To answer the following questions: What influence did TA have, and which actors drove that? This study investigates how, why, and under what conditions TA can strengthen evidence-informed road safety LMICs and describes implications for the design of TA programs.

Methods A team conducted a realist evaluation with a multiple case study design to analyze the implementation of BIGRS in Accra, Bogotá, and Mumbai. Key informant interviews and documents were collected and analyzed using an iterative, retroductive approach. A program theory for BIGRS was developed, drawing from empirical evidence and diffusion of innovation theory.

Results TA can improve road safety capabilities and increase the uptake of evidence-informed interventions. The design of TA, TA providers, and TA recipients are most influential in achieving the former; city and national contexts are more influential in achieving (or preventing) the latter. To improve road safety capabilities, BIGRS generated a novel, city-specific analysis that shifted the focus of road safety towards vulnerable road users. Hands-on capacity building, tailored to specific implementation needs, improved ‘how-to’ understanding of the safe system approach.

BIGRS and city officials launched pilots that brought the safe system approach to life to increase the uptake of evidence-informed interventions. This built confidence in new approaches by demonstrating successful implementation and reduced the risk of change by gauging stakeholder sentiment. But pilots could only reach the scale the city and national contexts allowed. The role of city champions and their authority, road safety governance structures, existing political prioritization, and socio-cultural norms were determining influences on scale-up.

Conclusion Cities’ differential experiences with BIGRS demonstrate the importance of designing technical assistance to meet the context. BIGRS’ program theory emphasizes the interaction of trust, credibility, champions and their authority, governance structures, political prioritization, and the implementation of international evidence in creating the conditions for road safety change.