Wednesday, November 27 by JerryFoster
Rt 571 Concept Illustration
Not only do traffic engineers prioritize safety lower than residents, the designs that supposedly increase safety cause more death and destruction. Why? Because motorists behave differently than engineers expect.
In 2012, there were 33,561 traffic fatalities, including 4743 pedestrians and 726 cyclists.
Traffic engineers’ safety improvements include paving wider lanes and shoulders, removing roadside trees, straightening tight curves, etc. According to AASHTO standards, “every effort should be made to use as high a design speed as practical to attain a desired degree of safety.”
Traffic engineers believe that designing for high speed will provide safety.
The crash data, however, show “wider lanes and shoulders were associated with statistically significant increases in crash frequencies.”
Noland reports that traditional “road ‘safety improvements’ actually lead to … increases in total fatalities and injuries,” because “this type of approach tends to ignore behavioural reactions to safety improvements”.
Dumbaugh reports that “a behavior-based understanding of safety performance is supported by research and literature in the field of psychology, which has focused on the subject of traffic safety as a means for understanding how individuals adapt their behavior to perceived risks and hazards.”
Marohn calls the traditional approach to safety “professional malpractice”.
Despite WWBPA recommendations, the design for Rt 571 in downtown West Windsor follows the traditional approach – 45mph design speed, another lane and wide shoulders – all in the name of bicycle and pedestrian safety.
We’ve seen that traffic engineers might improve safety by becoming better social scientists. Before following that, however, our next installment of Learning to Love Your Traffic Engineer will look at cost.
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Wednesday, November 20 by JerryFoster
Unlike residents, our traffic engineers prioritize speed and volume over safety and low cost – why? It’s how they were trained.
We’re long past the era where roads provide orders-of-magnitude improvement, e.g. from walking to motoring, but policy still encourages speeding, e.g., engineers design for 5-10mph over posted speed, so 74% of drivers on Rt 1 in Plainsboro exceeded the speed limit recently.
Going faster means getting there faster, right? Only if you’re on the mythical open road – in densely populated New Jersey, we have traffic.
Speed can work against getting there faster in traffic, since cars stay further apart – the best volume throughput is at 30-46mph. Improved signal coordination and speed harmonization allow people to get there faster even though they’re going slower, by delaying the onset of stop-and-go congestion.
Historically, traffic increased year after year, but in 2004 per capita volume (vehicle miles traveled) declined (!), followed in 2007 by a total volume decline as the recession took hold. Though the Great Recession ended June 2009, total volume remains at recession levels, and per capita volume continues to slide.
Is it the end of “build it and they will come”? If so, engineers will have one more reason to change their priorities. In our next installment of Learning to Love Your Traffic Engineer we’ll look at safety.
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Wednesday, November 13 by JerryFoster
It’s hard to learn to love our traffic engineers – they don’t see the same world we do, and don’t want to talk about it. Why not? Have you been to a public meeting?
The public has issues – many residents have not learned to disengage knee-jerk thinking, do their homework or propose constructive suggestions. Some are hostile to any government action, including road projects.
We choose to live in West Windsor because of the promise of safety, good schools, open space and convenient train commuting. We love our cars, but don’t want traffic in our neighborhoods.
Charles Marohn, an engineer and planner, identifies the different values of residents and engineers. In order, residents prioritize safety, low cost, traffic volume and speed, while engineers prioritize speed, volume, safety and cost.
Value divergence shows in the effort to improve walking and biking along Cranbury Road. Despite WWBPA recommendations, residents’ public comments and numerous yard signs asking motorists to Drive 25, traffic calming was rejected as a project goal.
We’re determined to learn to love our engineers, so in our next installment we’ll focus on the most divergent values – speed and volume.
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Wednesday, November 6 by JerryFoster
New Jersey traffic engineers don’t see suburbs, destroy downtowns with arterials and have refused to adopt road designs for neighborhoods. How will we learn to love them?
We have to understand that traffic engineers love solving problems, just not social problems. They’ll design how to move cars through an intersection, but not how to preserve or create a downtown, increase property values or reduce pollution – yet the intersection design can affect all these other goals, positively or negatively.
Although we’ve been building roads for millennia, we’re just realizing how motor vehicle traffic affects society. Using a computer analogy, traffic engineering is moving from the green screen to the graphical user interface – people want a richer experience, including multiple ways to get where we’re going.
Traffic engineers must learn to see themselves as social scientists, concerned with how people in addition to motorists interact with the roadways – residents, runners, dog-walkers, cyclists, etc.
People are puzzling – we love our cars, but hate traffic – how can engineers solve the dilemma? Find out in the next installment of Learning to Love Your Traffic Engineer – What the Public Wants.
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