Road safety is a very specific niche area and very few international donors actually consider it as a priority and offer limited funding for it. However, we do compile such grant opportunities as and well available at this link: https://www2.fundsforngos.org/category/accidents-and-traffic/.
Seed grants for road safety is another rarity but if your project proposal is highly innovative, then many environmental donors or healthcare donors may also be interested in supporting your work.