Crash Frequency Minimization with Severity Mitigation in Road Geometric Design Using Chance Constraint Programming Optimization

Table 6

40 MPH model estimation results.

Significant variable	Coefficient estimate	t-statistic	Variable notation
Constant	−3.39	−12.07
Indicator of 10 ft lane width for each direction	0.06 (0.39)	0.56 (6.71)
Indicator of 11 ft lane width for each direction	−0.33 (0.71)	−2.27 (6.14)
Directional average daily traffic per lane	0.0002	12.88
Indicator of 2 lanes for each direction	−0.38	−3.28
Segment length	1.17	7.08
Indicator of each direction on Cornhusker highway between N 29th st and N 33rd st	1.01	0.09
Indicator of each direction with average daily travel in vehicles per lane less than 10000	1.79	10.145
Dispersion parameter	5.03	1.08
Number of observations	830
Log-likelihood with constant only	−1649.98
Log-likelihood at convergence	−1113.51
McFadden pseudo R-squared	0.33
Chi squared	1072.95
Info. criterion: AIC	2.71
Finite sample: AIC	2.71
Info. criterion: BIC	2.77

Random parameter, the standard deviation of parameter distribution is shown in parentheses.