Table 3

Effect of the 2015 and 2019 traffic enforcement regulations on total collisions, collisions resulting in injury and mortality due to road traffic collisions in Mexico City

	Total collisions			Collisions resulting in injuries			Mortality from road traffic collisions
	IRR	p	95% CI	IRR	p	95% CI	IRR	p	95% CI
2015
Step level change 2015	1.057	0.197	0.971 to 1.151	1.031	0.595	0.922 to 1.153	0.960	0.580	0.829 to 1.111
Pre-2015 trend* ^**	0.998	0.084	0.995 to 1.000	0.996	0.019	0.993 to 0.999	0.999	0.099	0.998 to 1.000
Post-2015 trend† ^**	0.997	0.000	0.997 to 0.997	0.997	0.000	0.996 to 0.997	0.997	0.000	0.996 to 0.998
Slope difference – 2015‡	0.999	0.536	0.997 to 1.002	1.000	0.795	0.997 to 1.004	0.998	0.038	0.997 to 1.000
2019
Step level change 2019	1.028	0.600	0.927 to 1.140	1.066	0.435	0.909 to 1.250	0.788	0.133	0.577 to 1.075
Pre-2019 trend§ ^**	0.997	0.000	0.997 to 0.997	0.996	0.000	0.996 to 0.997	0.996	0.000	0.995 to 0.997
Post-2019 trend¶ ^**	0.997	0.358	0.991 to 1.003	1.011	0.028	1.001 to 1.021	1.023	0.008	1.006 to 1.041
Slope difference – 2019	1.000	0.973	0.994 to 1.006	1.015	0.003	1.005 to 1.025	1.027	0.002	1.010 to 1.045

*January–December 2015 (mortality January 2013–December 2015).
†January 2016–December 2018.
‡Slope difference pre-post policy quantified as exponentiated interaction coefficient (coefficient β3 in equation 1, refer to methods).
§January 2016–7 June 2019.
¶8 June 2019–31 December 2019.
**Weekly change in the outcome.