Table 1. Comparison of County Characteristics Across Quartiles of EMS Response Timea.
| Characteristic | Median EMS Response Time | P Value | |||
|---|---|---|---|---|---|
| <7 min (n = 480) | 7-8 min (n = 629) | 9-11 min (n = 656) | ≥12 min (n = 503) | ||
| County Rurality | |||||
| Rural-urban continuum | |||||
| Urban | 292 (60.8) | 321 (51.0) | 183 (27.9) | 90 (17.9) | <.001 |
| Suburban | 68 (14.2) | 84 (13.4) | 55 (8.4) | 23 (4.6) | |
| Rural | 102 (21.3) | 179 (28.5) | 293 (44.7) | 156 (31.0) | |
| Wilderness | 18 (3.8) | 45 (7.2) | 125 (19.1) | 234 (46.5) | |
| Population density, people/mile2 | |||||
| <16 | 31 (6.5) | 53 (8.4) | 158 (24.1) | 278 (55.3) | <.001 |
| 17-42 | 67 (14.0) | 136 (21.6) | 236 (36.0) | 136 (27.0) | |
| 43-08 | 117 (24.4) | 174 (27.7) | 191 (29.1) | 68 (13.5) | |
| ≥109 | 265 (55.2) | 266 (42.3) | 71 (10.8) | 21 (4.2) | |
| EMS Time Intervals, Median (IQR), min | |||||
| On-scene time | 16 (14-17) | 17 (15-19) | 17 (15-20) | 19 (16-22) | <.001 |
| Transport time | 11 (9-14) | 13 (11-18) | 17 (13-22) | 23 (15-32) | <.001 |
| Measures of Access to Definitive Care | |||||
| Proximity to level I or II trauma center | |||||
| Within county | 132 (27.5) | 95 (15.1) | 17 (2.6) | 28 (5.6) | <.001 |
| Adjacent county | 160 (33.3) | 259 (41.2) | 252 (38.4) | 154 (30.6) | |
| No proximate trauma center | 188 (39.2) | 275 (43.7) | 387 (59.0) | 321 (63.8) | |
| Population ≤25 miles from HEMS base, median (IQR), % | 97 (37-100) | 85 (20-100) | 52 (1-93) | 13 (0-71) | <.001 |
| State Traffic Safety Laws | |||||
| Maximum speed limit >65 mph | |||||
| Urban highways and interstates | 180 (37.5) | 288 (45.8) | 289 (44.1) | 230 (45.7) | .02 |
| Rural highways and interstates | 409 (85.2) | 556 (88.4) | 599 (91.3) | 460 (91.5) | .003 |
| Primary enforcement of seat belt laws | 373 (77.7) | 482 (76.6) | 460 (70.1) | 260 (51.7) | <.001 |
| Administrative license suspension | 407 (84.8) | 521 (82.8) | 553 (84.3) | 403 (80.1) | .18 |
| Text messaging ban | 436 (90.8) | 560 (89.0) | 576 (87.8) | 400 (79.5) | <.001 |
| Population and MVC Mortality | |||||
| Estimated populationb | 123 029 515 | 77 014 040 | 24 786 836 | 14 633 730 | NA |
| MVC-related deathsb | 6031 | 5233 | 3097 | 1737 | NA |
| MVC mortality rate, deaths/100 000 person-years | 4.9 | 6.8 | 12.5 | 11.9 | NA |
| Crude mortality rate ratio, 95% CIc | 1 [Reference] | 1.27 (1.12-1.44) | 1.63 (1.45-1.84) | 1.95 (1.72-2.22) | <.001 |
Abbreviations: EMS, emergency medical service; HEMS, helicopter emergency medical service; IQR, interquartile range; MVC, motor vehicle crash; NA, not applicable.
a
Data are presented as number (percentage) of counties unless otherwise indicated.
b
Population estimates and MVC-related deaths shown are from the most recent study year (2015).
c
Estimated using empty negative binomial model.