VMT Isn’t the Problem

For several years, people interested in transportation and urban planning have been discussing the impacts of motor traffic (mainly private cars) on all sorts of things. Over the last several decades, planning in much of the world has trended toward catering to car traffic, often at the expense of other modes of transportation. A popular measure of how much traffic there is is vehicle miles traveled (VMT) which is as it sounds: a tally of how far vehicles are traveling. Here in America, that figure rose for several decades as more people drove more. All that driving has had a real impact on many different aspects of society.

In recent years, advocates are increasingly shining a light on the true effects of that impact, with many cities starting to take notice and advance (largely token) measures to address the imbalance. The advocates often point to VMT as part of the proof of the ills of the current transportation network in America and one state has even gone so far as to transition their traffic impact metrics to VMT instead of LOS that it is virtually everywhere else. But is VMT really the issue? Or perhaps a better way to ask the question is would the effects of cars on society be different if they weren’t going as far, particularly as it relates to the physical environment?

When approached from that point of view, the answer seems more clear: VMT is not the problem but merely a symptom. This will certainly come as a shock to many people who have argued that VMT is bad for several years. Certainly, there are several ills that increase as cars are driven more such as crashes, emissions, time spent away from family and home, and many other less-than-optimal outcomes. However, at the end of the day, VMT is just another metric that can be used to identify and describe the true problem: car-centric planning and design. But without acknowledging that the true problem is one of design priorities, not the metric, we risk taking the wrong approaches to addressing the issue because there are many car-centric solutions to the problem of high VMT which are ultimately detrimental to the goal of using VMT in the first place.

These solutions can take one of several forms. In some instances, new roads can shorten trip distances and there are even entire projects that shorten trip distances (i.e. grocery store in a community). Both of those types of projects can be completely car-centric and unusable by other forms of transportation, yet they can at least nominally, be recognized for reducing VMT because they technically do. However, few would say that such a project is actually beneficial to a community. New roads have the potential to induce driving while a project that brings shops closer but also plops a large parking lot in an otherwise quaint environment can degrade the quality of the neighborhood, including by ultimately injecting many more cars into a part of town that may have previously not been so heavily traveled.

At the other end of the spectrum, a people-centric environment can be detrimental to lower VMT by being designed to completely exclude cars or at least force through traffic to take a detour around the area that adds length to what would otherwise be a straight trip (see video below). Such a location sounds like it would be beneficial and desirable in many a community, but a focus on reducing VMT can lead to a project that would whittle away at the oasis in an attempt to provide a reduction in VMT. If that sounds familiar, that’s because it is the same issue that has long been a hallmark and the bane of the LOS metric and led to calls for its removal. Under LOS, car-centric projects were advanced, even at the expense of all other modes, because they were projected to “improve” vehicular flow to maintain certain levels-of-service. Similarly, absent astute guidance and engaged leadership, that status quo threatens to continue under the guise of reducing VMT.

Of course, the future is far from certain. Advances in autonomous and electric vehicle technology may well mitigate the more pressing issues of private car use by reducing crashes and emissions. However, the use of VMT as the metric to measure how car-centered society is may well prove to just be a stepping stone to a broader realization that cars and people just don’t mix and that places where the latter are living, working, and generally going about their lives are not places where cars should be unless they’re just visiting.

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