Just ran across this Wendell Cox piece from last fall about the relationship between passenger-rail service and traffic congestion. Cox makes an interesting point:

Passenger trains do not reduce traffic congestion. In fact, a material
expansion of passenger train service could increase traffic congestion
and impose economic losses.

In a study forthcoming from The Heartland Institute, I find there is
no case in which an expansion of passenger train service has resulted
in a material or sustainable reduction in traffic congestion. This is
because passenger trains reduce the competitiveness of freight trains,
resulting in the diversion of cargo from trains to trucks, thus
increasing traffic congestion.

Reducing traffic congestion should be an economic priority. A strong
body of research shows traffic congestion reduces economic growth,
increases product prices, and increases poverty by making it more
difficult for lower-income workers to get to and from work in urban
areas.

Passenger rail fans look to the shiny trains of Europe and Japan and
wonder why they don’t exist in the United States. They overlook that
the more intense (and highly subsidized) passenger train service in
Europe and Japan leaves little room for freight trains. As a result,
much of the freight that would move by train in the United States is
moved by trucks on European and Japanese roadways, making traffic
congestion considerably worse.