Two passive improvements will make a big difference.
1. Thirty foot height. Currently eighteen foot bollards are considered big barriers. These are the ones we see a few guys boosting another guy over, and see folks sitting on top of for pictures. Almost none of the people who fall from 18 feet will die from such a fall. More than half of people who fall from 30 feet, will die from the fall - those that don't die, are badly hurt/handicapped.
As an object falls, it accelerates. The difference in total speed/impact force between an 18 and 30 foot fall is dramatic. The psychological reaction when viewing those heights is hard-wired into our brains. 30 feet is much scarier than 18.
At eighteen feet, an untrained team of young men can boost each other, standing on their shoulders, three high. Forget about that at 30 feet - you would need circus acrobats, and lots of them.
2. Barrel top. If you watch shows like American Ninja, where people run obstacle courses, you can see that certain shapes and distances just exceed human reach and grasp. A three foot diameter barrel top is a showstopper to free climb over. It also provides no purchase for a grappling hook.
