THE electronic traffic signs sometimes show wrong info? Here’s why, and what might fix it

time2018/01/04

THE electronic traffic signs sometimes show wrong info? Here’s why, and what might fix it

Instead of displaying traveling times for getting through downtown Seattle, a sign overhead Aurora Avenue North on a recent morning commute displayed a secret, cryptic code — “*”.

Just kidding: The sign was simply on the fritz.

Dozens of electronic overhead boards, formally called dynamic or variable message signs, on freeways and streets throughout the metro area aim to warn motorists of traffic issues in real time. The messages can range from alerts about special events to closures to estimated traveling times.

But who monitors the signs? And why do they sometimes show useless or wrong information? We found those answers after a couple of people wrote to Traffic Lab, saying they noticed far-off traveling estimates recently.

Lisa Peterson, for instance, said an Interbay sign on her commute home to Crown Hill at one point said the miles-long trip would take just three minutes.

“That is physically impossible even without traffic,” she wrote. “Today, coming in, the sign said 10 minutes to downtown, but it took 10 minutes just to get to Belltown.”

Elaine Marklund, of Seattle’s Hawthorne Hills neighborhood, said a sign in the University District recently showed getting onto Highway 520 would take just seven minutes. It actually took her more than 25.

“It is frequently incorrect to the point of being worthless,” Marklund wrote.

And as it turns out, drivers are not the only ones who have noticed problems with the signs recently.

The Seattle Department of Transportation (SDOT), which operates 31 dynamic message signs on city streets, this month found “a significant lag” between their traveling-time estimates and the actual time it takes to get around, SDOT spokeswoman Mafara Hobson said.

The Washington State Department of Transportation (WSDOT) manages the system controlling what appears on state highway signs, except for a few in Seattle along Highway 99.

To fix the city’s system, Hobson said, crews last week reworked the way they use data for tracking real-time traveling patterns in the city. That process uses information from detection devices and traffic cameras on roads, as well as drive tests by SDOT workers.

That data feeds into computers at the Traffic Operations Center (TOC) in the Seattle Municipal Tower, where a team of engineers monitor and disperse the information via social media and the electronic signs.

“The TOC has found a new and better data processing system that consistently gives the most accurate travel times,” Hobson said in an emailed statement.

Crews have tested the new methodology several times, the statement said.

But that change alone won’t guarantee 100 percent accuracy next time you hit the road.

Tim McCall of WSDOT said drivers could notice incorrect traveling times when they are moving down a roadway as traffic backup is growing quickly or there is a recent incident causing issues ahead. The signs, which update every five minutes, are sometimes unable to keep up.

“What’s happening is, some drivers hit the road at the inopportune time, where it’s (congestion) building and those traveling times are escalating as drivers are filling the roadway,” said McCall, an operations engineer of intelligent transportation systems. “There’s only so much we can do. ”

Unlike the city system, which requires engineers to physically input what appears on the signs, WSDOT’s network runs automatically. That system uses detection devices with magnetic loops and radar signals to feed real-time information on speeds and congestion to computers — no humans necessary.

The timing of highway ramp meters is another example of a similar automated process.

“All of these inputs go into a backdoor program, which compiles this information on a given traffic route and calculates travel times,” said McCall, who works at WSDOT’s Shoreline Traffic Management Center. “Over time, we build up predictability.”

WSDOT says it has about 100 variable message signs on highways between South King County and the Canadian border. That does not include its portable, “static” signs that crews use around roadwork or other traffic blockages.

The Shoreline facility controls the overhead signs on Seattle freeways. It’s one of six Traffic Management Centers across the state that function as WSDOT’s “nerve center” for incoming and outcoming traffic data, much like SDOT’s control center downtown.

Another reason motorists may notice wacky displays?

A sign could be dysfunctional.

“We’re trying to do as much as we can to keep them working,” McCall said, noting that some signs are between 15 and 20 years old.