Understanding the socioeconomic effects of transport-related factors, specifically fuel prices and traffic fines on car use and road safety is an ongoing research topic. There is a significant need for studies focusing on low- and middle-income countries (LMICs) due to their specific economic contexts. To fill this gap, the impact of these interventions on monthly road fatality rates from 2005 to 2024 in Iran was analyzed using a SARIMAX model. Petrol prices and traffic fines were adjusted by per-capita-income to account for the mediating effects of economic conditions. Results showed that while petrol price-to-income ratio had negative correlation with petrol consumption (r = −0.729), the absolute petrol price had positive association (r = 0.734), highlighting the importance of adjusting fuel price for income when studying its impact on car use (and road safety) in LMICs. A 10% increase in petrol price-to-income ratio (traffic fines-to-income ratio), might be associated with 11.7% (8.3%) decrease in the expected fatalities per 10 million population. Accordingly, road safety improvement could be a substantial positive side effect of fuel subsidies reform. Moreover, traffic fines need to be regularly increased based on an economic indicator to maintain their long-term effectiveness. The possible impacts of three pricing policy scenarios were further discussed. The findings offer actionable guidance for socio-economic planners: calibrate income-indexed fines, adopt fiscally neutral fuel price adjustments with equity safeguards, and optimize enforcement deployment where marginal fatality reduction is highest. The framework is adaptable for anticipating and responding to future shocks in mobility and safety due to price/income hikes.