Requirements of a Safe Vehicle Intersection

It’s not about behavior and won’t be solved by traffic calming.

The Backstory

An intersection near my home causes numerous predictable accidents, which in turn inspired me to write a detailed study of the matter on Medium… and ultimately resulted in simple list of attributes of safe intersections published in that study.

Just recently, on July 29, 2024, another predictable accident killed one person and likely ruined the lives of several others at another killer intersection just 1/2 mile away on the same street. That second intersection violated one of my list of safe intersection attributes. In fact, I’ve warned my friends and family many times about that second intersection, “If you’re going to die on Stenton Avenue it will be at the intersection of Stenton and Evergreen.” On July 29th that’s what happened but fortunately for me, not one of my friends or family. And that recent accident has inspired me to separate out my list of safe intersection requirements… that is now this article.

Requirements

You don’t have to be highway engineer to understand what makes a safe intersection, you just need to be a good student of the physical world. Here’s the simple list of what it takes:

• A 90-degree cross (+) or “T” shape… no “5 points” nonsense or V shapes like those geometry problems you could never solve in high school.
• Level ground, no hills.
• Visibility from every direction, of the intersecting street, perhaps 50 yards to the left and right, depending on the speed of the roads. In other words, no trees or buildings that go within mere feet of the corner.
• No curves immediately on the approaches. No entry curves, exit curves, or through curves.

• No distracting (moving or illuminated) backgrounds, or backgrounds that interfere with your vision.

We could add some details about 12-lane roads intersecting with 6-lane roads (you know who you are), or unusual left turn circumstances, but the list doesn’t really change. Follow the rules above and, while you still might have some accidents, they will only be from behavior and acts of nature, not road design.

Things that Are Not Solutions

If your goal is to have more people die, pretend that the following will help and/or spend money on them. When the next person dies, maybe the family will give you credit in their obituary for being part of the problem instead of the solution.

• Traffic calming
• Red-light/traffic cameras
• More enforcement of the laws
• Signs
• Lane markings
• Blame it on behavior and say there’s nothing we can do about that.