Outdoor warning sirens

After adding my last post to Google Plus, a friend asked my thoughts on tornado sirens. I replied that I thought they provided a rather poor return on investment. This eventually lead to a day-long discussion with a coworker who disagrees with my assessment. Since I’ve never put my opinion on sirens in a blog post, I figure it’s time to do just that.

First, I am of the opinion that sirens serve an important role in public safety. In places like parks, golf courses, and common outdoor gathering areas, sirens are an excellent way of communicating a single message: “seek shelter”. Sirens are unable to communicate why shelter should be sought, when it is safe to come out (though some jurisdictions will re-sound sirens as an all clear), or what the threat is. Some siren systems lack battery backup, occasionally rendering them inoperable at the most inopportune times. Sirens also suffer, as do most alerting systems, of being stuck in a county-based warning system that no longer exists.

Although they are not intended to be indoor warning devices, some people still rely on them as their primary means of receiving severe weather alerts. When close enough to a siren, this can be fairly reliable, but it’s not always the case. My house is 1000 feet from the nearest siren and during tests it is quite audible (uncomfortably so when the windows are open). During heavy rain, it is not nearly as noticeable. I have little doubt that I would sleep through an overnight siren sounding if it happened during a heavy rain.

So what, then? Since the 1970’s, NOAA Weather Radio has served the country well. It provides both alerts and routine weather information around the clock. Unfortunately, it’s also stuck in the 20th century. County-based alerting simply cannot continue to dominate our warning dissemination systems. If the weather radio system were to send warning coordinates along with SAME codes, receivers could optionally determine if the alert needs to be sounded. In addition, most counties are served by a single transmitter. Each transmitter should have a redundant backup, located far enough away to be unlikely to fail from the same event (e.g. power outage, tornado), but still able to cover the assigned counties.

The current state of sirens in Tippecanoe County includes coverage of all areas I propose require it (and probably some that don’t). There are still, by my calculations (see note 1), approximately 25,000 people in the county who live outside the audible range of sirens. In order to cover the entire county’s land area, the initial investment would be $960,000 to $2.7 million (see note 2) with an annual maintenance cost of $115,200-324,000. (see note 3)

I wanted to look at the costs for all thirteen counties served by the WXK74 transmitter in Monticello, but it turns out the siren count information is not easy to find. WTHR in Indianapolis did some of the work for me, but the rest had to be independently researched. Sadly, some Emergency Managers don’t want to disclose even a count of the sirens in their county. As a result, I was only able to obtain authoritative siren counts for Cass, Clinton, Howard, and Tippecanoe Counties.

Using the same strategy as for Tippecanoe County, I calculated what it would take to get these four counties to 100% siren coverage. The recurring costs are $774,00 to $1.44 million. This after an initial investment of $6.42-12 million dollars. And remember, that’s just for four of the fourteen counties, only 30% of the land area covered by WXK74 (roughly 65% of the population).

What would happen if instead of sirens, we added a second transmitter site and bought every household in the covered area a $50 weather radio? The cost of the transmitter would be about $75,000 (see note 4). Buying the radios would bring the cost up to roughly $9.84 million, which is in the range of covering 65% of residents with sirens.

Of course, this is entirely academic. Sirens are funded at the county level, whereas weather radio is a federal project. It’s not easy to just move the money around. There’s also the alert-granularity issue that needs to be resolved.

Given the economics and the richness of information, it makes sense to push for more radios instead of more sirens. Sirens have their place, but those places are limited. The Indiana Department of Homeland Security guidelines would suggest that many local cities and towns should not have sirens at all (except for parks). Ultimately, weather alerting requires a defense-in-depth approach. Sirens are one layer in certain situations. Weather radios are another, more broadly applicable layer.

A third layer is the Wireless Emergency Alert (WEA) system that is being deployed. Unfortunately, it requires a relatively modern smart phone, so I expect the penetration rate is still fairly low. It, too, suffers from a lack of geographic granularity (although probably better than either weather radio or sirens), and sparseness of information (WEA messages are limited to 90 characters). There’s also people who don’t have their phone by their side at all times. Some people actually leave their mobile devices in other rooms sometimes? Quelle horreur! Disturbingly, WEA does not interrupt phone calls, meaning a long gab session will result in you receiving a warning after it has expired.

Given budgets and politics at all levels of government these days, I’m sad to say that I don’t see any of the existing deficiencies being resolved any time soon.

1. Approximation is based on the assumption that coverage is 100% for Lafayette, West Lafayette, Dayton, Clarks Hill, Battle Ground, and Otterbein and 0% for the rest of the county. This is demonstrably untrue, but the best I can do without making it a in-depth GIS project.

2. The cost per siren is taken from an MLive.com article. Coverage calculations assumes no overlap and no gaps in coverage. Number of new sirens needed is calculated with a 1 mile and 1.25 mile service range. Actual cost would be higher, since the existing sirens have some overlap and are not located in the most geometrically-pleasing manner.

3. I tried to find out what percentage of the Tippecanoe Emergency Management Agency’s budget this would be, but I could not find a solid budget online. There’s probably a whole post about government transparency in this.

4. The cost of adding a new transmitter was based on a USDA grant program to add new transmitters. I took the first five pages of the grant awards and the median award for kilowatt transmitters is the value I used.

Some statistics for local counties where I could find siren data:

County Sirens Area (mi^2) Population
    Sirens/sq mi
Sirens/1k people
Cass 26 414.85 38,966 0.0627 0.6672
Clinton 12 405.25 33,224 0.0296 0.3612
Howard 8 293.92 82,752 0.0272 0.0967
Montgomery 24 505.44 38,124 0.0475 0.6295
Tippecanoe 71 503.24 172,780 0.1411 0.4109

2 thoughts on “Outdoor warning sirens

  1. I think that all counties should have warning sirens close to their houses
    So that they would know when to take shelter in their basements or storm shelters and sirens are a great
    Thing to have and weather radios are good to but the weather radios are not loud enough like the warning sirens
    Are and I think that warning sirens are a good thing to have and it will be a big investment to the other counties that don’t have
    Warning sirens at all. And I am a huge fan of warning sirens.

  2. Pamela, thanks for your comment, but I have to disagree with you. We live very close to a siren (well within the 1.5 mile range that seems to be the norm) and when a tornado warning happened in the middle of the night last week, my wife didn’t wake up. Unfortunately, our weather radio just died, but if it was still working, it would have been unavoidably loud. Many radios have a volume control. Either way, buying and maintaining enough sirens to make sure every house can hear it even when it’s raining in the middle of the night is prohibitively expensive. Especially as you get into rural areas. Sirens really only make sense in densely populated areas, or areas where people congregate outdoors such as parks.

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