I have found measuring in typical American neighborhoods that PM2.5 is raised the most when people burn wood for recreation or heat in the evening. It is much higher in the evening with a few neighborhood fire pits than during rush hour with a few diesel vehicles around.

This is also when residents have asthma symptoms too. To be fair they are more likely to be home.

So it is not cut and dry but if possible I would love to get rid of vehicle emissions as some particulate is too fine to measure.