Have you ever considered that building new roads might influence
more people to get into their cars? Many towns are now made up
of large segregated areas of industrial "parks", shopping "parks"
and vast residential suburbs without even a corner store within
walking distance.

That's not new roads causing extra traffic, that's out-of-town shopping
centres and retail parks causing extra traffic.

Unfortunately, councils are all too keen to grant permission for these
things, but they don't bother improving the road network in the area to cope
with the inevitable increase in congestion. Just look at the roads around
any Ikea store, for instance.