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Table 2 Odds of farm equipment crashes occurring on Iowa road segments calculated using Logistic Regression

From: The effects of roadway characteristics on farm equipment crashes: a geographic information systems approach

  Farm equipment crash
  cOR (95% CI)a aOR (95% CI)b
Road characteristics
Traffic volumec
 0–30 Ref Ref
 31–101 1.93 (1.54–2.40) 2.00 (1.60–2.49)
 102–360 1.69 (1.35–2.12) 3.76 (2.97–4.77)
 361–1250 3.26 (2.66–4.00) 7.43 (5.90–9.34)
 1251+ 3.88 (3.17–4.74) 7.00 (5.38–8.85)
Speed limit (mph)d
  < 35 Ref Ref
 35–45 3.59 (2.75–4.68) 3.03 (2.30–3.99)
 50–60 4.64 (3.92–5.49) 8.05 (6.59–9.84)
 65+ 4.02 (2.87–5.64) 3.52 (2.42–5.14)
Road typee
 Interstate 0.59 (0.26–1.31) 0.60 (0.27–1.35)
 US route 4.53 (3.77–5.44) 4.86 (3.99–5.91)
 Iowa route 5.70 (4.80–6.78) 5.98 (4.97–7.20)
 FTM routef 4.70 (4.14–5.34) 4.67 (4.11–5.32)
 Local route Ref Ref
Surface type
 Paved Ref Ref
 Unpaved 0.65 (0.58–0.73) 0.97 (0.86–1.11)
Road widthg
 mean(sd) 0.95 (0.91–0.99) 0.90 (0.86–0.94)
Shoulder widthg
 mean(sd) 1.44 (1.39–1.49) 0.94 (0.89–1.00)
  1. aCrude odds ratios and 95% confidence intervals
  2. bAdjusted odds ratios and 95% confidence intervals; bolded estimates were significant at the α=0.05 level.
  3. cAverage Annual Daily Traffic (Total annual traffic volume/365)
  4. dModel mutually controls for Speed Limit, Traffic Volume, and Shoulder Width
  5. eModel mutually controls for Road Type, Surface Type and Road Width
  6. fFarm to market route
  7. gUnit: 5 feet