[WEC-All] good article about traffic light timing as traffic mitigation

[Mark Robinowitz]

http://www.mcclatchydc.com/homepage/story/36912.html

Posted on Tuesday, May 13, 2008

There is something that can be done about the traffic
By Frank Greve
McClatchy Newspapers


WASHINGTON — Fine-tuning controls on the nation's traffic signals  
would cut U.S. road congestion by as much as 10 percent,  
transportation experts estimate.

It would also reduce air pollution from vehicles by as much as a  
fifth, cut accidents at intersections and save about five tanks of gas  
annually per household, according to the National Transportation  
Operations Coalition, an alliance of federal, state and local traffic  
departments and equipment-makers.

That's the good news. The bad news is that the average local traffic  
department earned an overall grade of D on the alliance's latest  
report card. Streamlining intersections is happening in only some  
cities and states, even though it's eminently doable.

"People who say we can't do anything about congestion are wrong. We  
can do lots," said Joel Marcuson, a specialist in urban intersections  
who's with the Jacobs Engineering Group Inc. in Phoenix.

Right now, however, three out of four of the nation's 300,000 traffic  
signals need replacement or timing adjustments for optimum  
performance, according to the U.S. Department of Transportation.

Among the obstacles are a nationwide shortage of skilled traffic  
engineers, unfocused local political leaders with tight budgets and  
stodgy local traffic departments. For that matter, federal aid that  
could ease congestion goes mainly to building and maintaining roads.

Nonetheless, lots of cities and at least seven states — California,  
Florida, Washington, Minnesota, Maryland, Georgia and Texas — are  
finding ways to move traffic through intersections faster, according  
to the transportation engineers group.

And where does your metropolitan area stand?

It could need improvement, traffic engineers say, if your answer is no  
to any of these questions:



	• Can you sometimes make it through six to eight consecutive  
intersections on green lights?


	• Is there useful traffic information on the radio and on roadside  
message signs?


	• Is it rare that there's no cross traffic when you're stopped at a  
light?


	• Can you drive into the next jurisdiction without encountering  
congestion at the border?


	• Are predictable traffic jams, such as the post-game exits from  
stadium parking lots, handled adroitly?

Most traffic departments can do better at each of three levels of  
traffic management, Marcuson and other experts said: individual  
signals, coordinated signals and regional traffic management.

Technologically, most U.S. traffic signals remain very 20th century,  
said Philip Tarnoff, director of the Center for Advanced  
Transportation Technology at the University of Maryland in College Park.

Roadside or centralized timers drive most of them by changing lights  
at scripted intervals, he explained. "They tell the signals: `It's 6  
a.m. Use timing schedule A until 9 a.m. Then use timing schedule B  
until 4 p.m.'"

If timers are accurate, and the prescribed signal intervals are based  
on accurate and recent traffic surveys, these systems can do as well  
as fancier ones in typical traffic situations.

That's a big if, however. Most timed systems aren't refreshed and  
adjusted at the three-year intervals recommended for busy  
intersections or ones that see big changes in traffic due to new homes  
or businesses. In the industry self-report card issued last year,  
traffic departments nationwide earned a collective F for traffic  
monitoring and data collection, which are key to well-timed  
intersections.

"As a result, signals may not operate based on actual traffic  
conditions, resulting in delays," the National Transportation  
Operations Coalition's report concluded. The 417 departments in 47  
states on whose data the grade was based control nearly half of all  
U.S. intersections.

Even perfectly tuned timer-dependent signal systems can't adapt to  
unpredictable roadway events such as accidents, construction and bad  
weather. Together, those factors cause half of U.S. traffic  
congestion, according to Transportation Department statistics.

For all these reasons, Tarnoff and many other traffic engineers favor  
adaptive signal-timing systems first adopted 30 years ago in the  
United Kingdom and Australia. They measure traffic minute-to-minute  
with cameras or in-pavement sensors and automatically adjust signal  
times to maximize flow for existing conditions, including accidents,  
construction and bad weather.

These adaptive signals haven't caught on with local U.S. traffic  
departments, however. They're costly and challenging to program, and  
initial local U.S. experiments with foreign-made systems failed. So  
did efforts to come up with home-grown ones.

Samuel Staley, director of urban and land use policy at the Reason  
Foundation and a specialist in transportation, said traffic  
departments often lack the money, skill and local political power to  
innovate with adaptive technology.

"They're resistant to change, particularly if it involves learning a  
new technology," Staley said. "The small cities don't have the depth  
of technical knowledge, and the big cities, while they have depth of  
knowledge, also have a lot more politics that resists innovation."

Whatever the reason, more than 95 percent of U.S. traffic signals  
today are still timer-driven, Tarnoff estimates.

That makes more difficult the next step in signal streamlining:  
synchronizing a succession of lights so that motorists flow through  
them smoothly at the posted speed.

Timer-based signals at intersections typically gain or lose a few  
seconds a year, Marcuson said. Over two or three years, he continued,  
the drift can make synchronized traffic stop-and-go.

So can adjacent jurisdictions, such as municipalities and counties,  
whose traffic departments don't work together. That's commonplace. A  
third of the traffic departments responding to the report card said  
they did no signal coordination across their boundaries.

Regionalized traffic management is the secret in U.S. metropolitan  
areas that move traffic best. They include Las Vegas, Milwaukee,  
Minneapolis-St. Paul, Los Angeles, Seattle, Kansas City, Denver,  
Houston, Miami-Dade County and the Washington, D.C., metropolitan area.

Among the most resourceful is Portland, Ore., which installed carbon  
dioxide emissions monitors at intersections before it improved their  
flow. The lower pollution that the monitors recorded enabled Portland  
to claim pollution-reduction credits that it sold for $560,000 on the  
carbon offset market. The money helped pay for Portland's intersection  
improvements.

Lakewood, Colo., another community that closely tracked before-and- 
after conditions, found that synchronizing lights at just 16 of its  
intersections delivered huge benefits. They included a daily savings  
of 635 hours in driving time, 172 gallons of gas and 758 pounds of  
pollution emissions, according to Denver's regional traffic authority.

Richard Plastino, Lakewood's director of public works, described the  
gains from improved intersections as "one of the few low-cost  
alternatives...to physical reconstruction of intersections and streets."

Then there's the real-life gain. Seattle, for example, retimed and  
synchronized more than 500 intersections between 1998 and 2002. The  
clearest result was a 20 percent drop in congestion on three of the  
city's major arteries.

As then-Seattle Mayor Paul Schell, the effort's leading proponent,  
argued at the time: "It's the one investment we can make in the near  
term that will make a difference in people's lives every day."

ON THE WEB

For a primer on optimized traffic signals, go tohttp://www.its.dot.gov/jpodocs/repts_te/14321.htm

To view a 13-minute Transportation Department video on improving  
intersection flow, titled "It's About Time," go to:http://ops.fhwa.dot.gov/arterial_mgmt/outreach.htm

To read the latest transportation industry report card on local  
traffic department performance, go to: http://www.ite.org/reportcard/

A LOOK AT SOME STATES' TRAFFIC SOLUTIONS

Texas, a U.S. leader in traffic signal efficiency since the mid-90s,  
adjusts its state-operated signals every two or three years to reflect  
changes in traffic volume. Once in three years is a national goal  
unmet in many states. Austin, the capital, earned a rare grade of A on  
its National Traffic Signal Report Card for providing proactive annual  
maintenance to all the city's lights at no added cost to taxpayers.

Washington state coordinates the timing of half the 1,000 traffic  
signals that the state is responsible for. It checks the timing of  
signals on busy arteries every two-and-a-half years. That compares  
with a three-year standard unmet in many states. In addition, the  
transportation department now reports directly to the governor rather  
than to a transportation commission.

Minnesota, which is among the nation's leaders in traffic control,  
retimes signals on the state's main arteries every two years, said  
Steve Misgen, a Twin Cities metro traffic engineer. Most states and  
communities struggle to adjust their traffic signals every three  
years. Most signals can be adjusted from a central control center in  
Roseville, he added. The state's ratio of benefits to costs is well  
above 60 to 1, Misgen said, counting only gas savings from less  
waiting time at intersections.

Maryland is a leader in coordinating traffic corridors; about half of  
the 2,700 signals that the state controls are linked to other signals  
to optimize traffic flow, said Eric Tabacek, the division chief of the  
state office of traffic and safety. Maryland adjusts signal timing  
every three years — and has done so since the mid-1990s. It's a  
standard that many states are struggling to meet. In addition,  
Maryland is experimenting with intersection video monitors that  
continuously adjust traffic light timing to maximize traffic flow.

Florida, which is among the nation's leaders in traffic control, gets  
credit for its success in linking city, county and municipal systems  
to improve traffic flow, most recently in the Sarasota-Bradenton area  
and around Tallahassee. It's also a leader in managing lights from  
regional command centers. Mark Wilson, deputy state traffic operations  
engineer, said that checking the timing of Florida's signals every  
three years or less is a key goal.

Georgia focuses much of its energy on the 20-county area around  
Atlanta when it comes to traffic signal improvements. Since 2005, it's  
cut travel time in Atlanta's traffic corridors by 18 percent and time  
stopped by 39 percent, said Yancy Bachmann, assistant state traffic  
engineer. Macon and Columbus have also seen traffic signal  
improvements, he said.

California has new money for traffic signal improvements, unlike most  
states. A 2006 bond issue yielded $150 million for the Los Angeles  
area. Top priority there and elsewhere goes to intersection  
improvements that improve driving time, cut accidents and reduce air  
pollution. Those that involve multiple jurisdictions working together  
also are favored under the traffic signal initiative whose first  
grants are expected later this month.

(Researcher Tish Wells contributed to this story.)

McClatchy Newspapers 2008