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Are We There Yet? The Bias Of Traffic Engineering

Editor's Note: Walkable neighborhoods and bike-friendly streets are all the rage but its road rage and the legacy of decades of auto-oriented bias slowing the creation of complete communities. The impact of the automobile bias of traffic engineering is the topic of today's excerpt from Are We There Yet?

The shift away from auto-oriented neighborhoods to a design that is more friendly to pedestrians and bicyclists is difficult because the tools used on a daily basis by traffic engineers have a built-in bias toward the interests of drivers. Travel models, for example, predict the future need for roads based on the need in the past, instead of recognizing that the priorities of Americans are changing.

Studies have shown that people who live or work near transit are more likely to use it. This may seem like a no-brainer but conventional transportation models that are used to determine how many roads and how much parking should be built assume that every person, no matter where they live, will make the same transportation choices.

“Level of service” or LOS standards are geared so as to always prioritize the movement of cars: Every change to a street — whether it involves adding a bike lane or painting a crosswalk — must be assessed in terms of the impact on car traffic. If the change slows car travel, cities must spend significant time and money on additional analyses and “mitigation measures” before even minor changes can be made.

Before 1991 all roads built in the U.S. and paid for — partially or in full — with federal funds had to meet guidelines in the American Association of State Highway and Transportation Officials Green Book, the official book of highway design. This book, long considered the bible of traffic engineering, referred to pedestrians as “traffic flow interrupters” during the 1990s.

“Travel models and LOS standards are a deadly duo used to get rid of traffic congestion — it’s tantamount to using a rototiller to get rid of weeds in a flowerbed,” writes Gary Toth, transportation director for the national nonprofit Project for Public Spaces (PPS), on the PPS blog. “Sure you get rid of the traffic congestion and you get rid of the weeds, but it’s time to acknowledge that the collateral damage is too great. In ridding our communities of the weeds of traffic congestion, we have also pulled out the plants that made our gardens worthwhile in the first place.”

Modes of travel

Amount of space required to transport the same number of people on a bicycle, car and a bus.

In a 2011 Engineering News-Record story, traffic engineer Sam Schwartz defends his profession but also opines: “We are the GEICO Neanderthals of society. As a profession we have continued to build more roads, wider roads, and faster roads while knowing full well we were running out of capacity and making transport systems less efficient.” Schwartz cites the Brooklyn Bridge as an example, writing that when it was built as a rail and walking bridge it handled 430,000 people daily, but after it was “modernized” in the 1940s to remove rail and boost car capacity, its “daily person-carrying volume dropped to 180,000.”

The inefficiency of a transportation system focused on single-occupancy vehicles has troubled some transportation experts. “Cars are immensely convenient,” says Dan Sturges, a former car designer at GM, “but we all know the problems — billions of dollars a year sent to the Middle East, growing greenhouse gas emissions, traffic, noise pollution, the paving over of green space. Across the nation about 50 percent of urban land is dedicated to transportation, and in Denver, where I live, the average car has only 1.1 occupants — making the car an immensely inefficient contraption.”

The City of Munster, Germany Planning, Department illustrated this idea with just three pictures. See graphic : How much space does it take?

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