Fort Worth and Arlington can already activate sirens to alert their communities about tornadoes and other emergencies, but both are working to get more detailed information into residents' hands.
In October, Fort Worth is expected to become the first Tarrant County city to launch a hazard alert system designed to provide audio messages to blind residents and video messages in American Sign Language to deaf residents.
The city estimates that 50,000 residents could benefit from the free subscription service, which would send alerts to smartphones or computers.
"It will help us get a message to citizens who are not currently getting that warning," said Juan Ortiz, the city's emergency management coordinator.
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Enrollment in the Accessible Hazard Alert System is expected to begin next month, he said.
Arlington is considering joining cities such as Fort Worth, Pantego, Kennedale and Roanoke that can send audio messages to home or business phones or text alerts to cellphones or e-mail accounts.
Emergency management officials are reviewing six systems and are expected to make a recommendation to the City Council by December.
The city began reviewing the notification systems after the April 3 tornado, which damaged more than 500 homes and businesses along Arlington's western edge.
Two months earlier, several key thoroughfares were blocked after a Union Pacific train derailed downtown near City Hall.
"Be it man-made or a natural disaster, segments of the city could be impacted by something," Fire Chief Don Crowson said. "The ability to provide a local impacted community with awareness of what is occurring may be a useful tool for us as we manage a response to a particular situation."
No funding has been identified to buy a system, which could cost more than $100,000 a year, city officials said.
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The system does the reverse of what a 911 call does by sending warnings to the public. It gives cities an additional way to warn residents to take shelter, especially when hail, high winds or loud televisions and radios could make the outdoor sirens harder to hear.
Since the mid-1990s, Fort Worth has been able to send audio messages to all land lines or just those in a specific area, Ortiz said.
During the West Nile virus outbreak, that system has been used several times to notify residents within one mile of a reported human case or a mosquito pool that tested positive for the virus, Ortiz said.
Fort Worth also sent out a citywide message this summer to its nearly 300,000 households informing residents how to protect themselves from the virus.
The system has its limitations, though: It can make only 48 calls at a time, Ortiz said. That's why it makes more sense to use the sirens to notify residents about rapidly approaching severe weather.
"It would obviously take a while to reach the whole city," Ortiz said. "You've got to use it for the right scenarios."
Arlington officials have encountered a similar problem with speed during system testing. It would take an estimated six hours to call Arlington's nearly 93,000 households, Assistant Fire Chief David Carroll said.
"Most big cities don't use these for weather. There are too many people to call at one time. The infrastructure isn't there," Carroll said. "We are finding it is not going to be very useful for weather situations."
But such a system could be helpful to notify specific sections of Arlington about emergencies that could affect them -- such as a school lockdown or a train derailment that is blocking intersections, Carroll said.
Smaller cities like Pantego and Kennedale do use their warning systems to notify residents about dangerous weather.
Pantego doesn't have its own siren system but relies on sirens in nearby Arlington, Fire Chief Thomas Griffith said. But after the April 3 tornado, the town began making automated phone calls to about 1,400 home and business lines every time the National Weather Service issued a severe-weather alert for Tarrant County, Griffith said.
"People get busy. They are preoccupied. They don't always have time to look at the weather or listen to the news," Griffith said. "In the middle of the night when you are sleeping, you don't know there is a storm outside. That is when it is really important."
Pantego residents can also register their cellphone numbers and e-mail addresses to receive alerts. The notification system costs the town about $3,000 per year.
"It's fairly rapid for use. We don't have that many phone numbers," Griffith said.
"If we activate it, we usually get a notice within a minute that everything has been called."
With the rapidly changing technology environment, Keller has held off on investing in a similar warning system because many residents have discontinued their land lines, officials there said. The city will continue to evaluate all the latest notification systems and invest in one that best suits residents' needs.
Fort Worth began allowing residents to sign up for emergency alerts through their cellphones or e-mail accounts about three years ago, Ortiz said. Trophy Club, Roanoke and Colleyville are among other area cities that use similar notification systems.
About 85 percent of Colleyville households are signed up to receive home-phone, e-mail or text alerts, which include weather emergencies, water problems or, more recently, human cases of West Nile virus, city spokeswoman Mona Gandy said.
One of the more memorable warnings came in 2009 when a tornado hit neighborhoods on John McCain Road.
Colleyville warned residents about 30 minutes before the storm hit.
Gandy said many credit the call with saving their lives.
Staff writers Susan McFarland and Nicholas Sakelaris contributed to this report.
Susan Schrock, 817-709-7578