A car is not designed to be a weapon except in the hands of a terrorist, like the ones in Charlotteville and Spain. Yes, lots of people got killed in car crashes through carelessness or recklessness so perhaps self-driven cars might help to reduce the carnage, no?
Guns, on the other hand, are weapons designed solely to kill whether by soldiers, police, criminals, terrorists, or law-binding owners. If guns aren't widely available and are restricted, lunatic killers might find it hard to get their hands on one as in Japan, Europe, Australia and New Zealand.
As for constitutional rights, I disagree with the conservative SCOTUS justices who overturned 200 years of precedents and said the 2nd Amendment includes individual right to keep and bear arms. They were Republicans who were just following the NRA and Republican Party's agenda which they supported.