When a person walks, uses a bike, or public transit for transportation, he/she very quickly realizes most of our street designs give very little thought to the needs of these other modes. That goes for the layout of most of our cities, as well as much of our car-centered architecture. Most people assume this is the natural order of things and must have always been this way, but as an historian I know that our built environment has a history and the more I studied the writings of those who think about such things, the more I encountered the name of Jane Jacobs.
Who was Jane Jacobs? Her talents were so wide-ranging, it’s hard to pin down a description, really. She was a mother and a housewife, a self-taught architectural analyst and critic, a journalist, what we would call today a “community organizer,” a social critic and a crusader for the survival of human-centered city life. She attended classes at Columbia University and even authored a history of the Constitutional Convention called Constitutional Chaff, which examined the rejected suggestions of the framers. She was the author of numerous other books and articles, but she is best remembered today for her classic 1961 critique of mid-20th century urban planning, The Death and Life of Great American Cities. She is a prime example of a socially engaged public intellectual. What enduring wisdom does Jane Jacobs offer a half century after her most important work was published?
I became especially intrigued with Jacobs after reading Anthony Flint’s excellent Wrestling With Moses: How Jane Jacobs took on New York’s Master Builder and Transformed the American City, which tells the story of her epic battle against Robert Moses and his plans to use “urban renewal” and expressways to remake Manhattan in the 1950s and 60s. The efforts of Jacobs and her neighbors to stop a number of ill-conceived car-first projects almost certainly saved her Greenwich Village and Washington Square Park neighborhood from destruction by highways. She was a pioneer in the fight to reclaim cities (and social life) from automobile domination. Such efforts become even more urgent as we wrestle to tame the outsized carbon footprint of the automobile-based civilization we created in the 20th century. As David Owen and others have argued, cities with good transit and people-friendly (not car-friendly) design have the potential to light the way to a much more sustainable future for a large proportion of the world’s population.
In Death and Life, Jacobs offered a critique of the dominant post-WWII schools of urban planning, with their focus on decentralization, grandiosity, and bland uniformity. She provided a detailed discussion of elements that make neighborhoods and streets attractive, livable, and safe, using her own Greenwich Village neighborhood as an example. She coined terms such as “eyes on the street,” to describe how neighbors in dense neighborhoods watch out for each other, and the “intricate sidewalk ballet,” to describe the relative safety and rhythm of busy city streets. She celebrated short blocks with wide, tree-lined sidewalks that were pedestrian and child-friendly, and appreciated the diversity of people, uses, and buildings in urban neighborhoods. Finally, she zeroed in on the ways cities could be saved from destruction, including a particularly fascinating chapter on the inherent conflict between living cities and automobility.
Jacobs argued that the social life of the city was incompatible with a large volume of automobiles. She claimed not to be anti-car, saying the problem was not cars themselves, but “vehicular dominance,” resulting “mainly from overwhelming numbers of vehicles to which all but the most minimum pedestrian needs are gradually and steadily sacrificed.”  The virtue of walkable streets was not the complete absence of cars, she noted, but the absence of automobile domination. This meant that cities must “reduce the domination by cars” in order to create walkable, bikeable, and livable streets.
Too much dependence on private automobiles and city concentration of use are incompatible. One or the other has to give. In real life, this is what happens. Depending on which pressure wins most of the victories, one of two processes occurs: erosion of cities by automobiles, or attrition of automobiles by cities. 
She detailed how city street space was eroded by the widening of streets, the marginalization of pedestrians, highways and, especially, parking lots. These efforts to accommodate the insatiable space requirements of cars elbow aside all other uses and create dull streets and “border vacuums” that effectively become anti-social space destructive of the multitude of uses a healthy city street possesses. She also detailed the symbiotic relationship between the automobile and sprawl, leading to more automobile dependence, in turn leading to more space given to cars, ad infinitum.
Her observations help us to see that the erosion of city livability stems from the prioritization of the private automobile, and also that its use is further encouraged by these measures, what urban planners now refer to as “induced demand.” In what might be seen as the precursor to today’s idea of “road diets” bike lanes and pedestrianized streets, Jacobs advocated “giv[ing] room to other necessary and desired city uses that happen to be in competition with automobile traffic needs.”  She made the radical argument that if we don’t give in to the demand for greater automobile convenience by, say, widening roads or providing additional parking garages, and if we provide alternatives, such as transit, enough people will avoid driving, and thereby reduce the absolute number of vehicles on the road and improve the quality of life for all.
While there are additional examples of this today, in 1961 one of the few example of this phenomenon (what urban planner Jeff Speck calls reduced demand) was Jacobs’s own experience blocking a planned highway through Washington Square Park. Traffic engineers predicted gridlock if the highway was not built, but the predicted cars never materialized. “Where have the traffic commissioner’s annual millions of cars gone instead?” she asked. She came up with the radical idea that there is no absolute number of drivers any more than there is an absolute number of transit users or bicyclists. The numbers of each, she pointed out, “vary in response to current differentials in speed and convenience among ways of getting around.”  In other words, when the design of our roads and cities makes driving the fastest and most convenient way of getting around, that is what people will choose to do. When we make other modes of transit more convenient and faster, the numbers will shift.
Attrition of automobiles operates by making conditions less convenient for cars. Attrition as a steady, gradual process . . . would steadily decrease the numbers of persons using private automobiles in a city. If properly carried out . . . attrition would decrease the need for cars simultaneously with decreasing convenience for cars, much as, in reverse, erosion [of other modes] increases need for cars simultaneously with increasing convenience for cars. [emphasis added, 363]
Her argument about induced demand was almost unheard of in 1961, and still escapes the grasp of many traffic engineers and politicians who think the answer to the problem of too much automobile traffic congestion is to make room for (and create further demand for) even more cars by widening roads and freeways, building more parking garages, supporting sprawl development, and so on. Here in Southern California I see it in the reluctance of some politicians to embrace road diets on the one hand and the misguided use of public transportation money to widen freeways and extend others (i.e., the multi-billion-dollar 710 extension that won’t die). Until and unless we decrease the convenience afforded automobile travel by, for example, making it more expensive through congestion pricing, higher parking costs, and so forth; and increase the convenience of other modes, such as bicycling and public transit, we won’t be able to “solve” the problems that ultimately stem from too many cars.
In real life, which is quite different from the life of dream cities, attrition of automobiles by cities is probably the only means by which absolute numbers of vehicles can be cut down. It is probably the only realistic means by which better public transportation can be stimulated, and greater intensity and vitality of city use be simultaneously fostered and accommodated. 
Herein lies a hard truth for those who advocate hybrids or EVs or self-driving Google cars as the solution to our environmental and transit woes. The problem with cars is only partially an issue of what comes out of the tailpipe. After all, Jacobs notes, at the turn of the 20th century cars were seen as a sanitary improvement over the heaps of horse excrement left by the previous dominant mode of transportation. Jacobs gets us to see that the problem is primarily one of numbers and scale, and that the number of cars is directly influenced by the design of space, and that use and convenience follow. The more space provided for cars, the less can be provided for people (unless you sprawl ever outward, which creates even more car dependent spaces). That is why she thought our key choice was the erosion of cities or the attrition of automobiles.
Creating streets that appeal to people and that are safe and convenient for pedestrians, bicycles, and transit requires mustering the political will to inconvenience drivers. It means shifting funding priorities to redesign of streets around transit, bikes and pedestrians. To paraphrase Bogota’s Gil Penalosa, we can have cities for people or cities for cars. We can’t have both. Mrs. Jacobs knew it. Will we learn it?