A New Jersey 'traffic study' wouldn't need lane closings
- 14 January, 2014 12:18
The explanation that New Jersey closed access lanes on the heavily traveled George Washington Bridge for a "traffic study" is a head scratcher for traffic engineers.
Engineers today use so-called microscopic traffic simulations to create virtual environments that can model driver behavior to road changes with exacting detail.
There's have plenty of data available for the simulations. One of the best sources are video camera systems that use software to count vehicles on roadways.
The simulation software can model the impact of road changes with precision and without any need to close lanes to test theories, according to several traffic engineers interviewed by Computerworld.
There is no evidence, in documents released late last week by investigators, that the Port Authority of New York and New Jersey considered computer models in lieu of a real world action. The Port Authority manages bridges and tunnels, airports, ports, and other critical systems in that region.
Instead, the Port Authority shut down two of the three access lanes for four days last September from Fort Lee to the George Washington Bridge without warning the public, citing a "traffic study."
After the lanes were closed, many people complained about it to the Port Authority, public officials and to local newspapers. The Port Authority was accused by one woman of "playing God with people's jobs" in a call to a Port Authority official, who made a note of it. It was among the documents released last week.
People weren't just late for work due to the disruption.
School buses and emergency vehicles were also delayed by an action that has led to multiple investigations of the administration of Republican Gov. Chris Christie. Some of the governor's top appointees orchestrated the lane closings, apparently as a type of retribution against Fort Lee's Democratic mayor, Mark Sokolich, documents have shown.
"Time for some traffic problems in Fort Lee," wrote Gov. Chris Christie aide Bridget Anne Kelly to David Wildstein, the Port Authority's director of interstate and capital project, who complied.
Real traffic engineering is a meticulous, safety-focused undertaking with some powerful software tools to work with.
"You certainly do not have to close lanes physically," said Joseph Hummer, chair of Civil and Environmental Engineering Dept. at Wayne State University. The impact of a lane closure can be modeled. Those models are accurate in the short-term, plus or minus a couple of percent, on measures such as travel time and delay, he said.
There is software available to project traffic changes 30 years out and give "good enough" answers for long-range planning purposes.
The most accurate tools, for microscopic analysis, includes equations for measuring the traffic flow of individual vehicles, which is something that gets to driver behavior, said Hummer.
A microscopic analysis can simulate when a driver changes lanes, speeds-up, slows down, how close do they follow the car in front of them, and the speed at which they follow, among other variables. It can update measurements every one-tenth of a second, said Hummer.
It is expensive software to run and is only used on big projects -- such as lane closures. The economic cost of the New Jersey lane closures more than justifies its use, Hummer says.
Eventually these models will get sophisticated enough to be able simulate "really odd driver behaviors" that can create accidents, and to predict collisions before they occur, Hummer expects. Collisions are relatively rare and are tough to model, but Hummer is hopeful that improvements in computing power and the underlying logic can solve this problem.
Lorenzo Rotoli, an engineer and vice president at Fisher Associates, a civil engineering firm in New York that works on roads, bridges and signal systems, uses the high-end PTV Vissim software for traffic modeling. He said the software can reproduce real-world traffic conditions.
"I would be pretty confident that if we knew exactly which lanes are closed we could replicate that, and it would show exactly how bad the backups are going to be," said Rotoli. He tempers his observations by noting that he has no insight in the Port Authority situation, but said "I can't imagine their particular scenario was so unique and so different that the higher end software (tools) couldn't have handled it," he said.
Traffic data for computer models can be collected in several ways. Tubes can be installed that register a pulse of air when a car passes over. Some sensors can be screwed or nailed into in a roadbed. Installing these systems may involve some short-term road closing. Also, people could be also be deployed to count vehicles.
On busy roadways, though, engineers are likely to use camera video detection with software that can count vehicles. That's the least intrusive method, and the documents released last week suggest that such a video camera system in installed on the George Washington Bridge.
Once engineers define what it is they are measuring, the data is gathered, and then an existing condition model is created. The model is calibrated against existing conditions, and from there the simulations are run to assess the impact of something like a lane closure or a road construction project, said Rotoli.
The computer models, which can show animated vehicles, bicyclists and pedestrians, can also be used to inform the public and officials about the impact of a road project.
New Jersey's alleged study increased risks to motorist as well as delayed their travels. "When there are delays people get frustrated they drive more aggressively and accidents happen, "said Rotoli.
Public notice, which was missing in New Jersey, is also important, the experts said.
In Los Angeles, for instance, in preparation for the Olympics in 1984, the public was warned for months by traffic engineers and the officials that traffic would be terrible. Consequently, "a lot of people adapted and the traffic wasn't as bad as we thought it would be," said Richard Dowling, a transportation engineer at Kittelson & Associates in California.
It's hard for engineers to come up with examples of road changes that were done, as in the case of New Jersey's lane closing, as an experiment to test something out.
"It's very unusual to use the public as a guinea pig," said Dowling.
Patrick Thibodeau covers SaaS and enterprise applications, outsourcing, government IT policies, data centers and IT workforce issues for Computerworld. Follow Patrick on Twitter at @DCgov, or subscribe to Patrick's RSS feed . His email address is email@example.com.
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