The safest road system in the US is the Interstate System, a 46,000-mile (74,029.8-km) network of highways across the country that was constructed starting in 1956. Its traffic fatality rate, or deaths per 100 million miles (160 million km) driven, is less than 1.0, while the average fatality rate for all roads in the US is about 1.5. The Interstate System was designed to be safer than regular streets because all traffic flows in the same direction, with no intersections, so there are fewer chances of collisions caused by sudden turns or not yielding when pulling out into traffic.
More about road safety:
California is the US state with the highest number of traffic fatalities, with about 4,000 each year.
In 2013, there were an estimated 1.24 million traffic-related deaths worldwide.
Before the Interstate System was built, the national average traffic fatality rate was 6.05 deaths for every 100 million miles (160 million km) driven.