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Table 3 Selected models for intersections

From: The variability of urban safety performance functions for different road elements: an Italian case study

Predictor Estimate Std. Error z- value p-value
All intersections
 (Intercept) 0.930 1.524 0.610 0.542
Ln (Total AADT) 0.285 0.106 2.675 0.007
Main AADT/Total AADT −6.870 2.021 −3.399 0.001
Type: Four-legged (reference: Three-legged) 0.443 0.105 4.210 <  0.001
Critical sight distance 0.005 0.002 2.762 0.006
Specialized turning lane (Yes – ref.: no) 0.496 0.114 4.362 <  0.001
Poor maintenance of pavements (Yes - ref.: No) −0.397 0.115 −3.444 <  0.001
Cycle path crossing (Yes – ref.: No) 0.327 0.122 2.677 0.007
Goodness-of-fit measures
 LRT (reference: null model) = 5.63 (df = 12), p = .934; LRT (reference: full model) = 161.11 (df = 12), p < .001
 Nagelkerke R2 = 0.283, AIC = 1877.6
 Over-dispersion parameter (theta) = 2.84 (std. error: 0.52)
Interval of continuous predictors
 Total AADT: 4175–41,560 vehicles/day, Main/Total AADT: 0.50–0.62, Critical sight distance: 0.0–139.5 m
Three-legged intersections
 (Intercept) 4.696 2.895 1.609 0.108
Ln (Total AADT) 0.366 0.220 1.661 0.097
Main AADT/Total AADT −16.376 3.711 −4.413 < 0.001
Number of entering lanes on the main road −0.211 0.119 −1.768 0.077
Critical sight distance 0.006 0.003 2.009 < 0.001
Specialized turning lane (Yes – ref.: no) 0.927 0.228 4.061 < 0.001
Traffic control 1: give-way/stop (ref.: no control)a 0.359 0.214 1.675 0.094
 Traffic control 2: traffic lights (ref.: no control)a 0.377 0.289 1.306 0.192
Traffic control 3: main + turning lights (ref.: no control)a 0.556 0.313 1.777 0.076
Cycle path crossing (Yes – ref.: No) 0.900 0.235 3.830 < 0.001
Goodness-of-fit measures
 LRT (reference: null model) = 63.39 (df = 9), p < .001; LRT (reference: full model) = 5.79 (df = 9), p = .761
 Nagelkerke R2 = 0.292, AIC = 610.4
 Over-dispersion parameter (theta) = 5.26 (std. error: 2.75)
Interval of continuous predictors
 Total AADT: 5420–32,300 vehicles/day, Main /Total AADT: 0.50–0.62, Critical sight distance: 0.0–139.5 m, Number of entering lanes on the main road: 0–4
Four-legged intersections
 (Intercept) −0.127 1.623 −0.078 0.938
Ln (Total AADT) 0.372 0.108 3.450 0.006
Main AADT/Total AADT −5.427 2.624 −2.068 0.039
Critical sight distance 0.004 0.002 2.102 0.036
Specialized turning lane (Yes – ref.: no) 0.410 0.134 3.060 0.002
Poor maintenance of pavements (Yes - ref.: No) −0.446 0.151 −2.961 0.003
 LRT (reference: null model) = 77.98 (df = 5), p < .001; LRT (reference: full model) = 7.55 (df = 12), p = .819
 Nagelkerke R2 = 0.225, AIC = 1263.6
 Over-dispersion parameter (theta) = 2.79 (std. error: 0.59)
Interval of continuous predictors
 Total AADT: 4175–41,560 vehicles/day, Main /Total AADT: 0.50–0.61, Critical sight distance: 1.6–100.0 m
All intersections (alternative)
 (Intercept) 1.713 1.513 1.132 0.257
Ln (Total AADT) 0.371 0.103 3.613 <  0.001
Main AADT/Total AADT −9.502 2.161 −4.397 <  0.001
Median on the main road (Yes – reference: No) 0.226 0.117 1.930 0.054
Critical sight distance 0.004 0.002 2.359 0.018
Type of intersection (Signalized – ref.: Unsignalized) 0.268 0.104 2.580 0.010
Poor maintenance of pavements (Yes - ref.: No) −0.321 0.118 −2.730 0.006
Cycle path crossing (Yes - ref.: No) 0.253 0.123 2.058 0.040
Goodness-of-fit measures
 LRT (reference: null model) = 124.59 (df = 7), p < .001; LRT (reference: full model) = 8.29 (df = 8), p = .406
 Nagelkerke R2 = 0.222, AIC = 1914.1
 Over-dispersion parameter (theta) = 2.40 (std. error: 0.41)
Interval of continuous predictors
 Total AADT: 4175–41,560 vehicles/day, Main/Total AADT: 0.50–0.62, Critical sight distance: 0.0–139.5 m
Signalized intersections
 (Intercept) 2.390 2.293 1.043 0.297
Ln (Total AADT) 0.407 0.142 2.863 0.004
Main AADT/Total AADT −11.302 3.586 −3.152 0.002
Type: Four-legged (reference: Three-legged) 0.452 0.182 2.479 0.013
Critical sight distance 0.004 0.002 1.986 0.047
Specialized turning lane (Yes – ref.: no) 0.307 0.148 2.076 0.038
Poor maintenance of pavements (Yes - ref.: No) −0.630 0.148 −4.243 <  0.001
Presence of bus stops (Yes – ref.: No) −0.914 0.357 −2.559 0.010
Goodness-of-fit measures
 LRT (reference: null model) = 95.60 (df = 7), p <  0.001; LRT (reference: full model) = 4.39 (df = 9), p = 0.884
 Nagelkerke R2 = 0.320, AIC = 1078.2
 Over-dispersion parameter (theta) = 3.08 (std. error: 0.71)
Interval of continuous predictors
 Total AADT: 5800–41,560 vehicles/day, Main/Total AADT: 0.50–0.61, Critical sight distance: 1.6–139.5 m
Unsignalized intersections
 (Intercept) −2.604 2.185 −1.192 0.233
Ln (Total AADT) 0.759 0.163 6.343 <  0.001
Main AADT/Total AADT −7.868 0.173 4.389 0.001
Type: Four-legged (reference: Three-legged) 1.036 2.406 −3.270 <  0.001
Median on the main road (Yes – reference: No) −0.998 0.329 −3.031 0.002
Specialized turning lane (Yes – ref.: No) 0.516 0.204 2.523 0.012
Cycle path crossing (Yes - ref.: No) 0.997 0.193 5.156 < 0.001
Presence of sidewalks (Yes - ref.: No) −1.008 0.331 −3.042 0.002
 LRT (reference: null model) = 65.07 (df = 7), p < .001; LRT (reference: full model) = 11.96 (df = 11), p = .367
 Nagelkerke R2 = 0.238, AIC = 769.8
 Over-dispersion parameter (theta) = 8.11 (std. error: 6.14)
Interval of continuous predictors
 Total AADT: 4175–31,500 vehicles/day, Main/Total AADT: 0.50–0.62, Critical sight distance: 0.0–100.0 m
  1. aNote: The variable traffic control device was further disaggregated into: no control, give-way, stop control for unsignalized intersections, and into: traffic lights, traffic lights with dedicated left turning lights, traffic lights with dedicated right turning lights for signalized intersections