Ball banking

08172015-ball-bankingThere are words and phrases with multiple meanings that sometimes distract me and make my mind wander. I was recently in a meeting that centered around the term, “ball banking.” Immediately, my mind went to cleaning out my garage after my kids vacated the nest and left all their sports equipment behind. I gathered up 14 soccer balls, 30 softballs, 52 baseballs, golf balls, tennis balls, basketballs, on and on. I truly felt that I was a ball bank. That is not what I am talking about in this article.

I have a driving habit of challenging speed limits (the traffic control department has been helping me break this habit). The other day, I fell back into my habit when I saw a sign that told me there was a curve ahead and I should reduce my speed to 30 mph. My speedometer said I was traveling 60 mph. My first thought was, “I am going to die.”

The good news is that I didn’t die. However, it gave me another thought: “Why didn’t I crash and burn?”. I was clearly over the speed limit. Well, I found out at a meeting with the South Dakota Department of Transportation.

We had just completed a signage project for roads in the state’s Minnehaha County and part of the project brought the answer to my question. Signage speed limits on curves was part of the project. Chad Stensland, one of our engineers, gave a great description of the process for establishing the speed limit on a curve, which leads us to ball banking.

bank-finalThe Federal Highway Department established a procedure for testing the speed limit on a curve. A mechanism is put in the car that has a ball that sits on a rail system. The driver drives their vehicle on the curve at a posted limit. The ball slides on the rail. If you’re going too fast while banking the curve, the ball slides on the rails, and when it hits a specified trigger point, a buzzer goes off to let you know you’re driving too fast.

You go through the curve again and again at lower speeds to eventually determine what speed limit should be posted on the curve. That posted speed is approximately 60-80% of a safe travel speed.

Curve Ahead - Slow Down! Wyoming, USA.Thank goodness that there is science behind posting a curve and that you don’t crash and burn when you’re one mph over the speed limit. It got me thinking…

  • What if I am driving on bald tires?
  • What if there is rain on the road?
  • Would I remember that I slide off the road if I’m standing still?

I’ve decided to reduce my speed and believe that the posted speed is established for my safety. Thank goodness that there are companies like Ulteig that have tested the curves and so that we know the signs posted are accurate.


About the author

Bob is our account executive in the Government market. He has nearly four decades of experience in municipal engineering and development in rural areas, small towns and larger cities. He brings a wealth of expertise to help provide ideas that lead to long-term solutions for our clients.