Regarding the issue of density vs density, or the comparable value of low- to mid-rise density versus high-rise density, brought about by economists being perhaps overly simple minded, the city of Melbourne commissioned an interesting study comparing densities of various places around the world. The most interesting part though is that "density" in this study isn't limited to residents or dwelling units, but also jobs per hectare (= about 2.5 acres) and cars per hectare and where they're parked. Related to building heights, the study found zero correlation between density and height in that density can occur in a variety of forms.
Another interesting study, not so much in the findings (predictable), but in who commissioned this: the Arizona DOT finds that land use intensity actually has an inverse relationship to congestion. In other words, higher intensity, density places have less congestion. The reason is because more transportation choice are available, including walking via proximity. Note to all transportation planners: you can not dissect transportation patterns from land use nor vice versa, land use's impact on transportation patterns. They are inextricable.
Lastly, Forbes has some new numbers on yearly ownership and maintenance costs for cars ($8,220) and bikes ($308) and that if Americans replaced one 4-mile car trip with a bike trip, the country would save $7.3 billion per year. These are simple numbers unfortunately. I see $7.3 billion as a small number spread over 500 million Americans. The big numbers come in when we start multiplying the costs (or savings) exponentially over the infrastructure necessary for everyone to move by car (or otherwise).
Related to this, the common rebuttal to Yonah Freemark's lambasting of Dallas's proposal to build a highway within the same corridor that already houses 20 lanes of roads AND a light rail line. Freemark's critics suggest that you can't compare the theoretical 100,000 cars that the new highway will move to the 15,000 people the Green Line moves per day. This is faulty thinking on a number of levels.
First, if the object is to relieve congestion on 35 this isn't 100,000 new cars. So therefore the corridor is not moving any new people nor getting them out of cars. So the 15,000 that the Green Line moves is actually more than 35 / Trinity Tollroad would move netted above what it already does.
Except we know that is not how roads actually work. Due to induced demand and Jevons Paradox, by making driving more efficient, we actually "induce" more drivers onto the roads. So that would be potentially 100,000 new cars that have to be moved through the corridor, thus a self-fulfilling prophecy is the Trinity Tollroad. The transportation planners are right!.... Only in the false world they've established.
However, we shouldn't WANT 100,000 new cars per day on roads making our bad air even worse. The goal MUST be to get people out of cars. As the Arizona study points out (and countless others), more highway capacity only serves to spread the real estate market (and people) further and further apart from each other and their daily destinations. Thus, making driving and car ownership all that more necessary. And coerced.
If the goal is to actually alleviate congestion rather than throwing money at a problem that will only be exacerbated by current methodologies and measures, we would be reducing demand on the existing highways by tolling them. Not building new tollroads.
To jumpstart the local economy and the desirability (and livability) of Dallas and areas in and around downtown, we should be removing highway capacity not adding to it. If we're serious about downtown and surrounding areas, we should be trying to move traffic, but move the market. To favor areas in and around downtown. We're presently doing the opposite.