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

Table 10

Results of linear regression models for travel speed during 3:30–5:30 pm

Model summary for 25CBD
Dependent variable	Number of observations	Adjusted R square	Standard error
Vehicles’ travel speed	2250	0.226	5.363
Coefficient estimation
Independent variable	Coefficient	t-statistic	Variable notation
Constant	23.717	64.830
Indicator of 9 ft lane width	−7.934	−19.961
Indicator of 10 ft lane width	1.323	4.115
Indicator of 11 ft lane width	−3.497	−9.501
Number of vehicles in every five minutes	−0.026	−2.924
Model summary for 35NCBD
Dependent variable	Number of observations	Adjusted R square	Standard error
Vehicles’ travel speed	4864	0.119	6.143
Coefficient estimation
Independent variable	Coefficient	t-statistic	Variable notation
Constant	36.193	64.337
Indicator of 9 ft lane width	1.962	3.349
Indicator of 10 ft lane width	3.947	13.738
Indicator of 11 ft lane width	7.636	19.598
Number of vehicles in every five minutes	−0.067	−9.623
Model summary for 40 MPH
Dependent variable	Number of observations	Adjusted R square	Standard error
Vehicles’ travel speed	7754	0.205	4.734
Coefficient estimation
Independent variable	Coefficient	t-statistic	Variable notation
Constant	40.056	487.711
Indicator of 10 ft lane width	−5.211	−39.248
Indicator of 11 ft lane width	1.147	7.239
Model summary for 45 MPH
Dependent variable	Number of observations	Adjusted R square	Standard error
Vehicles’ travel speed	6082	0.588	4.651
Coefficient estimation
Independent variable	Coefficient	t-statistic	Variable notation
Constant	43.394	77.442
Indicator of 10 ft lane width	−6.839	−48.637
Indicator of 11 ft lane width	6.064	23.430
Number of vehicles every five minutes	−0.031	−6.433