Roads that are not straight, wide and well marked cause drivers to slow down naturally. Bushes trees and other landscaping can be used to make the road seem narrow which also makes people slow down. Having a good S-curve before the slow area works well too and many rural towns do this.
For a school zone you should probably stick a traffic light at the school entrance since that will allow you to create a traffic clusterfuck in order to slow traffic for the hours when you want it slow and not reduce the capacity of the road the rest of the time. Turning it into a 4-way stop would probably work well since people approach those slowly since they have to stop anyway.
If the aim is to lower to speed to 35mph, speed cameras?
In my fantasy world school drop off points would be 10 minutes walk from the school. But impounding sounds good too :)
Yeah. I'd wager that they will not be pleased when they catch some teenager catching air in his shitbox at 34.9mph.
... yes, that’s the point.
What if they put speed bumps on the motorway/freeway, to slow everyone down for roadworks?
FTA "and was built to slow cars to 35 miles per hour"
Yes use speed bumps to slow people to 20mph, not 35mph.
Obviously hitting a speed bump at 35mph would be a very bad experience, but that's a different device than what's represented in the article.
What alternative would you suggest?
As a parent of kids who cross the street to get to school, in my fantasy world, speed limits in school zones are enforced by impounding the offenders' cars.