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

Table 11

Logistic regression relating risk of “high” CO emissions to intersection type and test car driver.

	Number of trips with CO ≥ 129 mg	Number of total trips	Coefficient	Odds ratio	95% CI	p value
Intersection:
Roundabout	38	139		1
Signalized	70	153	0.662	1.94	(1.16, 3.24)	0.0114
Driver:
D2	19	108		1
D1	89	184	1.398	4.05	(2.27, 7.23)	<0.0001

(Likelihood ratio: χ² = 35.92, DF = 2, value < 0.0001).