Reduce traffic and it reduces emissions, if the culture is that you walk, cycle or scoot to school, when you become an adult you're more likely to keep that culture and look to walk, cycle or scoot where you can rather than assuming that driving is how you get about.
We used to walk past a house (510m to the school gate) where the kids were driven every day, some days we'd see then getting in the car, they'd overtake us, and then we'd walk past them as the car was being parked - only for the parent to drive back home again.
We've since moved house, so the distance to school is now at least 1.3km (so about double what we were doing before), we still walk it as whilst it'll be marginally quicker to drive, not by enough to make it worth the effort. In fact quite a few who live near us do walk, so driving short distances isn't universal.