Requiring cars to include more safety features will make people more safe by reducing traffic fatalities, right? Not necessarily. This blog post by Alex Tabarrok explains why not.
Bottom line: there is a trade-off between extra safety features and affordability. At certain levels of income, people will choose more of the latter before they choose more of the former. Taking away the ability to choose the latter may make these individuals choose no car at all and decide to use much more dangerous, but relatively affordable, motorcycles. Thus, regulations that make cars more expensive by requiring people to pay for safety features they would not buy if they were free to choose can make them less safe.