The City of Flint and the Genesee County 911 Consortium supplied six data files for analysis. Historical response data was validated programmatically with varying degrees of certainty. This is done by using a commercial database against which the 911 data street and address is matched. Within the City of Flint the data validated at a rate of approximately 93% and the remaining Genesee County data validated at a rate of approximately 76%. This was the result of free form formatting of address and intersection information, as well as differences in spelling between the source data and the geographic database used in validation. The validation rates are within acceptable ranges and will not materially or negatively affect geospatial analysis and plotting. Based on the six data files, the geospatial analysis provides a visual display of call locations. Figures 10 and 11 are the geospatial display of call distribution based on Genesee County and City of Flint data respectively. The geospatial analysis will also used to determine call density and response time intervals.
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Figure 11. Geospatial Call Density Distribution – City of Flint
The east/west line drawn across the map establishes a distribution of demand that considers both equal call volume and equal territory within Genesee County as follows:2
♦ Number of calls (demand) for each zone: approximately 1,475 calls per month
♦ Size of North Zone: 316.6 square miles
♦ Size of South Zone: 330.2 square miles
This geospatial data per zone is discussed later in this Appendix in the feasibility analysis of zones.
In order to allow for urban and rural response coverage, density bands were created by grouping data into one-kilometer grids. Each grid is then evaluated to establish that at least two calls occur per month in the grid. If so, that grid is labeled urban, if not, the grid is labeled rural. A methodology is employed to assign and avoid stand-alone grids by checking surrounding square kilometers and assigning a like label. The urban and rural titles indicate density bands and not actual rural and urban zones.
Figure 12 below displays the one-kilometer density grids. The one-kilometer density grid approximates .39 square mile. Red color grids quality as urban and the blue color grids quality as rural based on the definitions above.
2
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Figure 12. Display of Urban and Rural Density Grids – Genesee County
For any cell to be classified as urban (red color), the cell must have a call density of at least two calls per month based on historical data and at least half of the eight bordering cells must also have experienced two calls per month. All other grids are labeled rural (blue color).
The grids are used to establish optimal response coverage for response times of:
♦ Urban Areas at 8 minutes zero seconds (displayed as 8:00)
♦ Rural Area at 11 minutes zero seconds (displayed as 11:00)
The optimal response time goal is 8 minutes 59 seconds. In this analysis, one minute is reserved for the 911 call intake and dispatch of the vehicles.
An urban versus rural designation is made for several reasons. Providers will place ambulances where the most calls occur which tend to be the more densely populated areas. By doing so, providers respond to more calls, more quickly thereby meeting response time requirements and generating revenue more efficiently. If a requirement is made to respond to all calls in all areas at the same response time, regardless of the number of calls in an area or the distance between
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calls and hospital destination, then the system becomes more costly. Ambulances must be placed in outlying, low call volume areas in order to meet responses time standards. In this situation, there is a trade off at the policy level and a longer response time standard is designated for the outlying areas. Care issues can be offset if there are other first responders readily, particularly if they can deliver rapid paramedic response.
Continuing the analysis based on the geospatial information and the given the urban and rural grid designations, three distinct deployment plans were modeled:
1. Primary Urban response plan with rural coverage added. 2. Urban and rural balanced coverage plan.
3. Urban and rural balanced response plan but for two distinct zones.
Table 2 below is a posting plan analysis that achieves an 8:00 response time with 90 percent demand coverage. A 90 percent urban preference is noticeable by the fact that ambulances are situated in the urban core and none are in the rural areas (see Figure 13). This is for illustration purposes only and would likely not be utilized in a countywide system approach.
Table 2. PostPlan90 – Level 20
Name PolyNum Latitude Longitude Class Count Total Percent
1 1979 43.01191 -83.687351 U 1062 1062 35.99% 2 1624 43.065608 -83.675077 U 540 1602 54.29% 3 1747 43.047709 -83.736446 U 217 1819 61.64% 4 2047 43.002961 -83.797814 U 195 2014 68.25% 5 2564 42.922414 -83.625983 U 113 2127 72.08% 6 1965 43.01191 -83.515519 U 109 2236 75.77% 7 1442 43.092456 -83.613709 U 99 2335 79.13% 8 2335 42.958213 -83.711898 U 82 2417 81.90% 9 1447 43.092456 -83.675077 U 73 2490 84.38% 10 1691 43.056658 -83.773267 U 49 2539 86.04% 11 862 43.181952 -83.736446 U 45 2584 87.56% 12 1971 43.01191 -83.589162 U 39 2623 88.89% 13 1924 43.02086 -83.736446 U 18 2641 89.50% 14 2153 42.985061 -83.65053 U 18 2659 90.11% 15 2928 42.868717 -83.748719 R 58 2717 92.07% 16 1281 43.119305 -83.810088 R 56 2773 93.97% 17 2286 42.967162 -83.834635 R 33 2806 95.09% 18 2440 42.940314 -83.552341 R 24 2830 95.90% 19 3288 42.81502 -83.822362 R 24 2854 96.71% 20 1552 43.074557 -83.515519 R 22 2876 97.46%
Note: Class U = Urban Post (8.0 minute response area) Class R = Rural Post (11.0 minute response area)
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This plan provides urban coverage prior to establishing rural coverage. The first column indicates that it takes 14 vehicles on standby prior to attaining 90 percent coverage on demand. Deployment of the 14 vehicles to achieve 90 percent urban coverage is indicated on the map in Figure 13 below.
Figure 13. Primary Coverage – Urban Area
In modeling a balanced urban/rural coverage plan, lower levels of urban deployment are assigned because the additional rural units will offset up to 10 percent of the urban coverage requirements. Therefore, the geo-spatial plan is modeled at 80 percent urban coverage.
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Table 3. Balanced Urban/Rural Coverage Plan
Name PolyNum Latitude Longitude Class Count Total Percent
1 1979 43.01191 -83.687351 U 1062 1062 35.99% 2 1624 43.065608 -83.675077 U 540 1602 54.29% 3 1747 43.047709 -83.736446 U 217 1819 61.64% 4 2047 43.002961 -83.797814 U 195 2014 68.25% 5 2564 42.922414 -83.625983 U 113 2127 72.08% 6 1965 43.01191 -83.515519 U 109 2236 75.77% 7 1442 43.092456 -83.613709 U 99 2335 79.13% 8 2335 42.958213 -83.711898 U 82 2417 81.90% 9 1277 43.119305 -83.760993 R 175 2592 87.83% 10 2091 42.994011 -83.613709 R 70 2662 90.21% 11 1989 43.01191 -83.810088 R 67 2729 92.48% 12 2928 42.868717 -83.748719 R 58 2787 94.44% 13 855 43.181952 -83.65053 R 24 2811 95.26% 14 3288 42.81502 -83.822362 R 24 2835 96.07% 15 1552 43.074557 -83.515519 R 21 2856 96.78% 16 2465 42.940314 -83.859183 R 20 2876 97.46% 17 2710 42.904515 -83.969646 R 15 2891 97.97% 18 2438 42.940314 -83.527793 R 13 2904 98.41% 19 1286 43.119305 -83.871456 R 12 2916 98.81% 20 1594 43.065608 -83.306867 R 8 2924 99.09%
Note: Class U = Urban Post (8:00 minute response area) Class R = Rural Post (11:00 minute response area)
Figure 14 below represents the deployment plan to obtain required response times. Two of the locations are outside the county boundaries. This is shown strictly to indicate the high level of activity that is currently occurring there. For actual coverage those points would need to be brought back into the county. A mutual aid agreement should be developed to deal with cross county calls.
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Figure 14. Balanced Urban/Rural Coverage Plan
This model suggests that coverage of demand can be met with an urban and rural response mix. The number of ambulances needed for geographic coverage is added to the base number of ambulances needed to cover the call activity. This will give the total number of ambulances required to deliver the service. Adjustments are made to move the out-of-county position within the Genesee County boundaries. Figure 15 represents the suggested coverage posts.
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Figure 15. Balanced Urban/Rural Coverage Plan
Even after the adjustment to move posts within the County boundaries, post number 19 is in a barely usable location. The deployment model was further refined and posts were readjusted. This adjustment will correct the placement of the vehicles, which then forces a final redistribution of post locations. The final post coverage deployment is as follows in Figure 16.
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Figure 16. Geo-Spatial Modeling
The above posts represent only the modeled ambulance locations for optimal coverage of Genesee County. These are not fixed locations, but areas that ambulance (and the Sheriff’s Office paramedics) can use as a starting point. Over the period of 12 to 24 months, historical data can be used to build new prediction models for deployment.
Two-Zone Coverage
Two zones were created to ascertain deployment issues for that configuration. The same methodology was used to establish the zones as used above: balanced urban/rural percent coverage with an urban to rural mix for each zone. Figure 17 and Table 4 below show the results first for the north zone and Figure 18 and Table 5 show the results for a south zone.
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Figure 17. North Zone Balanced Urban/Rural Plan
The above posts would be the optimal ambulance locations to cover the North Zone. The limited call volume works against the optimization of coverage and is more difficult. It is likely to create a wandering ambulance syndrome in which an ambulance is posted to capture a small cluster of calls.
Table 4. Zone 1 (North Zone) Balanced Urban/Rural Coverage Plan
Name Number Latitude Longitude Class Count Total Percent
1 1624 43.065608 -83.675077 U 804 804 54.21% 2 1747 43.047709 -83.736446 U 218 1022 68.91% 3 1442 43.092456 -83.613709 U 99 1121 75.59% 4 1691 43.056658 -83.773267 U 74 1195 80.58% 5 1277 43.119305 -83.760993 R 146 1341 90.42% 6 1615 43.065608 -83.564614 R 67 1408 94.94% 7 1581 43.074557 -83.871456 R 26 1434 96.70% 8 855 43.181952 -83.65053 R 24 1458 98.31% 9 1683 43.056658 -83.675077 R 10 1468 98.99% 10 636 43.21775 -83.859183 R 5 1473 99.33% 11 1375 43.101406 -83.515519 R 3 1476 99.53% 12 1222 43.128255 -83.810088 R 1 1477 99.60%
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Figure 18. South Zone Balanced Urban/Rural Coverage Plan
The above locations would be optimal for coverage of the south zone. Table 5. South Zone Balanced Urban/Rural Coverage Plan
Name Number Latitude Longitude Class Count Total Percent
1 1979 43.01191 -83.687351 U 744 744 50.72% 2 1986 43.01191 -83.773267 U 169 913 62.24% 3 2564 42.922414 -83.625983 U 113 1026 69.94% 4 2335 42.958213 -83.711898 U 82 1108 75.53% 5 1965 43.01191 -83.515519 U 71 1179 80.37% 6 2043 43.002961 -83.748719 R 78 1257 85.69% 7 2209 42.976112 -83.613709 R 59 1316 89.71% 8 2928 42.868717 -83.748719 R 56 1372 93.52% 9 3288 42.81502 -83.822362 R 24 1396 95.16% 10 2465 42.940314 -83.859183 R 22 1418 96.66% 11 2617 42.913465 -83.552341 R 12 1430 97.48% 12 3104 42.841868 -83.736446 R 8 1438 98.02%
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