Skip to Main
Jack's Journal

Jack’s Journal: Ball Bank Indicator

9&10 Logo

Driving in these parts means navigating the curves.

The Michigan Department of Transportation designs the road and sets the speed.

In some cases, they post advisory speed limits to alert drivers they may want to slow down on those bends.

“When you design a curve, for instance, it’s not just what the land lets you do. It’s a combination of the land and engineering,” said Krista Philips, MDOT traffic and safety engineer.

When it comes to that, mathematics is used to calculate speeds.

So what make a curve dangerous?

“A combination of the friction available on the road, whether the pavement is dry, wet, icy, snowy and the speed you are going,” explained Krista.

Advisory speeds are posted when the speed limit of that road might be too much for that curve, which would create “discomfort” for you the motorist.

Recently, MDOT raised speed limits in some areas. So how do you check existing curves for proper speeds when those speeds are raised?

Simple: you use a ball bank indicator.  It’s been used for years.

It’s a simple manual device for verifying the degree of discomfort experienced in that curve.

“We had three segments in our area that went from 55 to 65. So, we drove those and tested those to see if our degrees of deflection indicator exceeded thresholds,” said Krista.

Several curves on 131 that went up to 75 had advisories kept at 70 because the ball bank indicator suggested that was a wee bit too fast.

For the record, advisory speeds are just that: suggested.  But when road conditions deteriorate, the smart driver heeds the advisory.

It might not be fancy but it works and keeps speeds safe, and that’s the whole point.

9&10 Logo

Local Trending News