How to drive traffic away

A few days ago, I was trying to take a streetcar in Toronto- and the
streetcar was just as congested as any suburban arterial. The
lines in front of streetcars were so long that I couldn't get into the
first streetcar. Or the second. Or the third.
Instead, I had to wait a few minutes (horrors!) for the fourth
streetcar.

I asked myself: what if streetcars only ran every
hour, instead of every few minutes? Would the streetcars be
equally crowded? Of course not. People would abandon the
streetcars and start to use cars (if they owned them) and buy them (if
they did not yet own them).

In my experience, there is an inverse
correlation between the amount of public transit service and the amount
of overcrowding on trains or buses: in places with extensive
service, overcrowding is a problem- but in places where public transit
is limited to hourly bus service (e.g. Jacksonville, Florida) buses
tend to be delightfully uncrowded, and usually I can not only sit in a
seat but put my bags on the seat next to me. In three years in
Jacksonville, I do not think I ever had to stand on a bus.

This methodology should tell us something
about how and when we build roads. If (as I have suggested) reduced transit service
means less congestion on transit, why should roads be any different?