Deaths and serious injuries from road accidents remain a serious issue in developing countries, including for adolescents, for whom they are the largest cause of death. This paper provides an assessment of interventions to reduce these deaths and injuries for adolescents in 75 developing countries. Methods We draw on new data on deaths and injuries by age, gender and accident type for the 75 countries, and on the road safety experience of developed and, more recently, of developing countries. Critical tasks are to identify key interventions in road safety, and to estimate their impact and cost. We incorporate these impact and cost estimates in a modelling framework to calculate the reduction in deaths and serious injuries achieved out to 2030, relative to the base case. Finally, established methods are used to value the economic and social benefits arising from these reductions, and hence to calculate benefitcost ratios. Results For the unchanged policy case, we estimate that there will be about 3 million deaths and 7.4 million serious injuries from road accidents for persons aged 10-24 years in the 75 countries to 2030. The preferred interventions avert one million of these deaths and 3 million serious injuries, at a cost of $6.5 billion per annum over 2016-30, or $1.2 per capita across the total population of these countries. After valuing the benefits of the deaths and serious injuries averted, we find a benefit/cost ratio of 7.6 for 2016-30, but of 9.9 if the interventions continue to 2050. Implications and Contribution Death and injury rates from road accidents have fallen sharply in developed countries in recent years. In the 75 developing countries studied, death rates are 5-6 times higher than in the developed countries and rose by 12% between 2000 and 2016. Road accidents are the leading cause of death for adolescents in developing countries. This study suggests that not only are the interventions available to address this problem, but they are available at a reasonable cost and would be high return investments, with benefits 7-10 times costs.