This fails to note an important factor in both suicides and car crashes, which is (in the US especially) strong popular preference for personal freedom over per

This fails to note an important factor in both suicides and car crashes, which is (in the US especially) strong popular preference for personal freedom over personal safety. People would rather be able to freely own guns (even if they are routinely used for suicide) or drive their own cars at fast speeds (even if it causes deadly accidents). Trains and planes get such strong safety assurances because they are typically commercially operated, so they are subject to another popular feature, which is commercial operators' permanent fear of liability lawsuits. It's much harder for people to accept to trade off personal freedom for safety than it is for people to demand safety guarantees in commercial transportation services.