I couldn't agree more with you.  However beware the 'new cities'/ New Urbanism movement, in that some of its prescriptions (eg on parking) are likely to be unsustainable in the long run (if people can't park, they won't go there/ businesses won't relocate there).

To make a mass transit line (or improvement) work you need to increase the density along this line.  The Toronto experience, where this was not allowed along the subway extensions (Spadina, Shepherd Avenue) is that you just stretch the core system, without increasing revenues enough to compensate-- Toronto now has a massive (unfilled) transit financial deficit.

The local municipalities in Toronto fought to prevent rezoning around the new subway stations as it would 'ruin the family quality of the neighbourhoods'.

http://www.toronto.ca/ttc/subwaymap.htm

(top left of the 'U', and later the right hand purple extension east)

Tall buildings, condos etc. are for other people.

I noted in the NYC City Official Plan the same thing going on, a deliberate down zoning of zoning in a number of neighbourhoods (mostly Queens and a few in Brooklyn).  The result, inevitably, will be that public transport will never be good enough there to divert significant road traffic.

The big win is in congestion.  Sprawl creates congestion, amazingly, concentration does not, because concentrated sites have fewer total car journeys (you walk from the office to the shops, you live closer, etc.).  You cannot fight congestion by building more roads: driving is a zero marginal cost activity, so people just drive more until the roads are filled up again.

The other big win is in housing affordability.  There is an economist at Harvard (Edward Gleaser) who has shown that almost all of the discrepancy in the last 30 years between housing prices on the coasts (rising much faster than real incomes) and in the centre of the USA (rising about with real incomes, if you strip out the last 5 years) is due to tightened zoning.  Effectively, NIMBYISM.

If you can build more densely, you can build more affordably.

It all depends on how you define "congestion". In the limit case of every house being half a mile away from anything else, with plentiful roads in between, there will be no congestion. You may have to drive 50 miles to the nearest store, but you'll be driving at the speed limit all the way, so that's no congestion. On the other hand, in a dense city, there's almost always some other car in front of yours, so there's 100% congestion, or at least, congestion for 100% of car trips. Even not taking into account the fact that many people will walk or take transit instead of driving, a 15 minute trip in Manhattan counts as congestion, while a 40 minute drive on an empty freeway counts as not congestion, even if both have the equivalent effect of getting you to the nearest mall.
I guess I was defining congestion in the context of an urban area.

The UK experience is if you build a road, it fills up-- it creates its own demand.

Similarly if you expand an urban area, you create flows of traffic to and from that new subdivision, leading to total traffic flow (on existing roads) than was there before-- households in the new subdivision want to work, shop and play in other places besides the new subdivision, and that creates traffic.

Jane Jacobs pointed out the reverse case very well: close a road, and a significant fraction on the traffic in question disappears (I think this happened on the West Side Highway in New York).

I think this all stems from the unique nature of car travel-- it takes up a lot of road space, but doesn't move many people (at 1.1 people per car which I think is the worldwide developed country average).

It's sprawl that creates traffic, rather than density per se.  What happens with density is people make shorter trips and fewer trips by car.

Since people like to live further apart, that seems to be human nature, the trick is to balance the two.

The other thing about car journeys that I recall, and I don't have the exact number to hand, is that something like 90% of car journeys are less than 5 miles ie in a place like the UK, easily doable by bicycle.

I don't know what the comparable US statistic is.

The countries that have tackled traffic congestion (Netherlands, Denmark) have done so by restricting traffic in favour of pedestrians, and aggressively encouraging bicycles.

"It's sprawl that creates traffic, rather than density per se.  What happens with density is people make shorter trips and fewer trips by car."
There you go. That's the more correct version of your statement, with "congestion" replaced by "traffic". Because "traffic" does have the implication of vehicle-miles-travelled, whereas congestion implies travel that is slower than some theoretical maximum.