Before-and-After Field Investigation of the Effects on Pollutant Emissions of Replacing a Signal-Controlled Road Intersection with a Roundabout

Table 9

Logistic regression relating risk of “high” CO₂ emissions to intersection type and trip direction.

	Number of trips with CO2 ≥ 58 g	Number of total trips	Coefficient	Odds ratio	95% CI	p value
Intersection:
Roundabout	45	139		1
Signalized	82	153	0.958	2.61	(1.57, 4.32)	0.0002
Trip direction:
Trip A	41	145		1
Trip B	86	147	1.331	3.78	(2.28, 6.27)	<0.0001

(Likelihood ratio: χ² = 41.96, DF = 2, value < 0.0001).