It is conventional wisdom in some circles that "comprehensive planning" and sprawl are polar opposites- that planning is the enemy of sprawl.
But in fact, a comprehensive plan is almost as likely as a zoning code to be pro-sprawl. Many of the land use policies that make suburbs automobile-dependent (such as wide roads, long blocks, low density, single-use zoning, etc.) can just as easily be found in a comprehensive plan.
For example, Jacksonville, Florida's plan(1) devotes most of the city's residential acreage is devoted to low-density residential use. The future land use map allocates 138,949 acres to that use, as opposed to 23,187 to medium-density residential and only 74 to high-density. (Land Use Element, Table L-20). The maximum density in the low-density area is 7 units per acre, barely enough to support minimal bus service. The plan adds that because zoning regulations will allow numerous districts with each residential category, "the average residential density in each category will be much lower than the maximum allowable density" (p. 67, Future Land Use Element). In other words, the plan contemplates that most of Jacksonville will have far fewer than 7 units per acre.
Needless to say, these low-density zones will be single-use, and are often so large that residents will not be within walking distance of anything but other houses. For example, my former neighborhood in Jacksonville (Mandarin, at the city's southern edge just east of the St. Johns River) is about six miles wide at its southern fringe- but the only commercial use is on two or three north-south streets, which means that most people will have to walk (or more likely, drive) a mile or two to reach any form of shopping at all. (Id., p. 153). The plan essentially ratifies the status quo, and in fact freezes it in place by allowing commercial expansion near residential areas only if such expansion "maintains the existing residential character." (Id., p. 35).
The plan also is ambiguous on cul-de-sacs, a common target of new urbanist commentators. The plan states in several places that cul-de-sacs are disfavored in new developments, but on the other hand states that the city "shall protect residential neighborhoods from cut-through non-residential traffic by providing appropriate traffic control mechanisms" (p.. 32) including cul-de-sacs.
The transportation element of the comprehensive plan also includes a few sprawl-generating provisions. In particular, it creates right-of-way minimums, such as a 150-foot minimum for major arterials and a 120-foot minimum for minor arterials (Transportation Element, p. 41). Major arterials are the most important commercial streets, while minor arterials are also typically commercial. (For examples, go to maps.google.com and look at "10000 San Jose Boulevard" to see a major arterial and "Baymeadows Road" to see a minor). Assuming 12 feet on each side for sidewalks and shrubbery, that means a major arterial might have about 125 feet of pavement and minor arterials 95 or so. Since the plan also provides that most lanes are to be 12 feet wide (16 for outside lanes, to add a turn lane) this means that major arterials will could have as many as nine or ten lanes, and even minor arterials will have five to seven. Either way, such wide streets are hardly walkable.
And Jacksonville's comprehensive plan is by no means the most pro-sprawl in existence; because Jacksonville has some walkable areas and a planning director who seeks to make the city more walkable, it does contain numerous countervailing features. For example, the plan suggests that parking can be in back of buildings instead of in front.
Suburban plans, by contrast, tend to be more aggressively sprawl-oriented. For example, Alpharetta, Georgia is an outer suburb of Atlanta. Its plan's(2) future land use map lists a variety of permitted densities; the highest density, for apartments, is only 10 units per acre (Ch. 7 at 7-14). Thus, the most compact areas allowed by Alpharetta's plan are only slightly more compact than Jacksonville's low-density areas. The plan also provides for numerous zones that are clearly incapable of supporting public transit, such as a "residential estate" area of 3-acre lots and a "very low density" area of half-acre lots. (Id.) The plan provides that only 4% of the city's land is to be high-density residential, as opposed to 54% for low-density residential (Id. at 7-10).
Moreover, what passes for compact development in Alpharetta is not intermingled with the city's offices; instead, high-density residential is a buffer zone between the city's large stock of offices (near the Georgia 400 highway) and the city's even larger stock of single-family homes. (See Future Land Use Map). As a result, most of Alpharetta's renters will not be able to walk to work even if they work in Alpharetta.
In sum, comprehensive plans will typically reincorporate the status quo. So if the status quo favors sprawling, low-density development, so will the comprehensive plan.