When seatbelts were made mandatory, the number of deaths on the road actually didn’t decrease, they stayed roughly the same! Similarly, it has been observed that motorists drove closer to the vehicle in front when the vehicles were fitted with anti-lock brakes.
Risk compensation is a theory which suggests that people typically adjust their behavior in response to perceived levels of risk, becoming more careful where they sense greater risk and less careful if they feel more protected
The most common form of this is called risk compensation, also called the Peltzman Effect, after Sam Peltzman, a University of Chicago economist who studied the phenomenon in the 1970s. His research found that as you introduced noticeable safety features, risky behaviour shifted accordingly.
See also: Religious Homeostasis
In the 1920s, when the big uptake in automobiles was getting underway, most people had a family member or a friend on a farm or in a factory who was familiar with machinery. Having a knowledgeable person accessible meant that you wouldn’t simply believe scare stories. They acted as a ripstop thread in the fabric of society.