"Fast" and wide roads don't actually help much with moving traffic around as there's such a phenomenon as induced demand. When more lanes are added to a road, more people are encouraged to drive and then the fast and wide roads get congested, especially where they join with smaller roads.
There's also the geometry problem. As more roads are built and more people travel by car, the various amenities get spread further apart (e.g. more parking required) which then makes them more difficult for people to walk/cycle to. This then gets more people to make a car journey when they previously might have walked which increases the amount of traffic. As more traffic builds up, more and wider roads are built which pushes everything further apart. This then encourages more and longer car journeys which results in more congestion - the solution to which would appear to be adding just one more lane to the roads.
The trick to solving congestion issues is to encourage as many people as possible to make short, non-car based journeys. Unfortunately, prioritising car journeys is almost always at the expense of other traffic.
There's also the geometry problem. As more roads are built and more people travel by car, the various amenities get spread further apart (e.g. more parking required) which then makes them more difficult for people to walk/cycle to. This then gets more people to make a car journey when they previously might have walked which increases the amount of traffic. As more traffic builds up, more and wider roads are built which pushes everything further apart. This then encourages more and longer car journeys which results in more congestion - the solution to which would appear to be adding just one more lane to the roads.
The trick to solving congestion issues is to encourage as many people as possible to make short, non-car based journeys. Unfortunately, prioritising car journeys is almost always at the expense of other traffic.