An Analysis of the Effects of Crash Factors and Precrash Actions on Side Impact Crashes at Unsignalized Intersections

Table 7

Random-parameter ordered logit model of injury severity for side impact crashes at T-junctions.

Y2 = T-junction crash injury severity		Model estimates		Marginal effects
Variables and description		β	O	C	B	A	K
Constant		0.128
Precrash actions (base: other behaviors)	Ran stop sign	0.844		−19.07%	5.85%	7.73%	5.02%	0.48%
	Failed to yield at stop sign	0.208		−4.09%	1.59%	1.56%	0.86%	0.08%
	Failed to yield at turn	0.262		−5.37%	2.00%	2.08%	1.18%	0.11%
Urban	Yes	−0.442		9.14%	−3.35%	−3.56%	−2.05%	−0.19%
Crash location (base: other crash locations)	Open country	0.220		−4.44%	1.68%	1.71%	0.96%	0.09%
	Residential area	−0.043		0.85%	−0.33%	−0.32%	−0.18%	−0.02%
	Shopping center	0.092		−1.82%	0.70%	0.70%	0.39%	0.04%
Lighting condition (base: other lighting conditions)	Daylight	−0.196		3.96%	−1.50%	−1.53%	−0.86%	−0.08%
	Dark without lighting	−0.039		0.76%	−0.30%	−0.29%	−0.16%	−0.01%
	Dark with lighting	0.089		−1.79%	0.69%	0.69%	0.39%	0.04%
Turn lane present	Yes	0.183		−3.67%	1.40%	1.41%	0.79%	0.07%
At-fault driver_speeding	Yes	0.916		−20.94%	6.16%	8.54%	5.69%	0.55%
At-fault driver_DUI	Yes	0.919		−21.03%	6.16%	8.58%	5.74%	0.55%
Gender	Male	−0.250		4.93%	−1.91%	−1.88%	−1.04%	−0.09%
At-fault age	21 years old or younger	−0.186		3.59%	−1.42%	−1.36%	−0.74%	−0.07%
	22∼31 years old	−0.190		3.64%	−1.44%	−1.38%	−0.75%	−0.07%
	32∼41 years old	−0.061		1.20%	−0.47%	−0.46%	−0.25%	−0.02%
	42∼51 years old	−0.045		0.87%	−0.34%	−0.33%	−0.18%	−0.02%
	52∼61 years old	−0.176		3.36%	−1.34%	−1.27%	−0.69%	−0.06%
	62∼71 years old	−0.151		2.89%	−1.15%	−1.09%	−0.59%	−0.05%
Point of impact	Front passenger side	−0.209		3.96%	−1.59%	−1.49%	−0.81%	−0.07%
	Back passenger side	−0.613		10.59%	−4.46%	−3.91%	−2.04%	−0.18%
	Bumper	1.013		−20.19%	7.45%	7.82%	4.51%	0.41%
	Driver door	0.003		−0.07%	0.03%	0.03%	0.02%	0.00%
	Passenger side behind the driver	−1.012		16.01%	−6.94%	−5.83%	−2.98%	−0.26%
Causal vehicle type	Passenger car	−0.435		8.64%	−3.31%	−3.31%	−1.85%	−0.17%
	Pickup	−0.590		10.57%	−4.36%	−3.94%	−2.09%	−0.19%
	SUV	−0.528		9.67%	−3.94%	−3.62%	−1.94%	−0.17%
Noncausal vehicle type	Passenger car	−0.599		11.83%	−4.53%	−4.53%	−2.54%	−0.23%
	Pickup	−0.871		14.93%	−6.25%	−5.52%	−2.90%	−0.26%
	SUV	−0.629		11.30%	−4.65%	−4.22%	−2.24%	−0.20%
Scale parameters for random parameters	Failed to yield at stop sign	0.097
	Male	0.869
Mu(01)		0.819
Mu(02)		2.003
Mu(03)		4.588
Summary statistics	Number of observations	10,750
	Log likelihood at zero L (0)	−10,403.858
	Log likelihood at convergence L (β)	−9,747.577
	Pseudo-R2	0.063
	Likelihood-ratio test (vs. regular ordered logit)	Prob. = 0.000
	AIC	19,569.2