Everyone has access to a road. Not everyone has access to rail. No business can run without access to road, most businesses can run without access to rail.
There is basically no way to compare rail vs roads and making some arguments based on that.
Everyone who don't own a car have significantly less access to roads than someone who do.
Of course it's possible to compare the advantages and drawbacks of different modes of transport. No society can function without roads, but it's still a question of priorities.
A lot less! So we (society) should be promoting cycling as much as feasible. Also bike parking, which is often forgotten. My town is very bike friendly in nearly every way, except there's no secure bike parking which limits which stores I can bike to.
> Everyone has access to a road. Not everyone has access to rail.
Similar argument can be made about highways to which not everybody has (direct) access, they are not a matter of life and death for most businesses and are heavily subsidized.
Do you think that it covers the cost of excess death caused by particle emissions and road fatalities?
We don't have the option to completely replace car infrastructure, but we shouldn't act like it isn't heavily subsidized.
That said, the positive externalities are also significant, but so are the positive externalities from rail traffic.