Tornado Siren Location
Ann Arbor, Michigan
Sandra Lach Arlinghaus
The University of Michigan
with input from those noted below.

Different strategies for locating systems of sirens exist in different locales across the nation.  In Ann Arbor, and elsewhere, sirens noise is designed to alert citizens in the outdoors.  Citizens who are indoors may hear the sirens but the requirement is that people outdoors be able to hear them.  Thus, spacing requirements between sirens becomes important.  When there are barriers to overcome (all else being equal), such as topography, buildings and street noise, one might expect sirens to be required to be more closely spaced than in flat, open countryside.  Indeed, a brief review of municipal requirements on the world wide web reveals that Oakland County, Michigan views each siren to be capable of covering about a one mile radius.  The Baltimore City Fire Department selects spacing at 3200 feet.

The sequence of animaps below, of Ann Arbor, suggests a locational strategy for pinpointing positions for new sirens.

In this first animated map, Figure 1,

Figure 1.  Red dots show existing tornado siren locations.  Green circles use the coverage radius employed by Baltimore, MD; yellow circles use the coverage radius employed by Oakland County, MI.

In the second animated map, Figure 2,

Figure 2.  Spacing between successive buffers of sirens is 1000 feet.

In the third animated map, Figure 3,

Figure 3.  In this view, connectivity of the road network, already within earshot of existing tornado sirens, is emphasized.

Finally, where might one consider locating new sirens (Figure 4)?

The cyan (turquoise) sets of concentric circles in Figure 4 fill these two gaps.

Figure 4.  Cyan concentric circles targe locations for two new tornado sirens.

Click here for a link to an interactive map made using ImageMapper 3.1 from .  Click on a dot on the linked map.  Portions of the underlying database associated with that dot will pop up next to the map.  The entries in the database are hypothetical and are present to suggest the range of power of this sort of map for organizing data.  There is no need for any extra plug-in so that users who are NOT administrators of a machine may also have access to municipal files, from their local public library, public university, or elsewhere.

Directions for future research:
  • Contour map of city
  • Triangulated Irregular Network (TIN) made from contour map to show topography
  • Superimposition of sirens on topographic map
  • Recommendations for siren location or relocation based on this finer analysis.

Input from:

Oakland County, Michigan

Baltimore, Maryland, Fire Department