BLOG: Speed limit pinball! - | WBTV Charlotte

BLOG: Speed limit pinball!

This Friday, June 5, marks a big day for anyone who drives in Mecklenburg County. The last leg of the I-485 loop finally opens. Sixty-seven miles long and more than 25 years in the making. 

I don't know about you, but I'm excited about this last leg because it's up in the area where I live and it's going to help cut off a lot of drive time for me when I head to the mountains and other areas!

I especially like that the speed limit along I-485 has been increased to 70 mph, although I'm not so sure about the reasoning. 

Yes, I understand I-485 was built to be able to handle 70 mph traffic. But the new limit was put into effect, in part, because traffic officials say when the speed limit was 65...motorists were actually doing 70 - 75 mph. So, should we expect traffic to be moving at 75 to 80 mph now that the speed limit is 70? All I can say is...please observe the speed limit!

And that leads me to the gist of this blog! 

In the years I've worked at WBTV, especially when I was doing Carolina Camera, I've traveled thousands of miles from one end of the Carolinas to the other! And in all those miles I've covered, nothing has confounded me more than the speed limit along highway 74 between Charlotte and Wilmington!

If you've ever traveled that route you know what I'm talking about. It's not the speed limit. Rather, it's the speed LIMITS...as in multiple speed limits! See for yourself, particularly along 74 between Wadesboro and Chadbourn. It's all four lane with the speed limit anywhere between 55 and 70 mph. 

It's somewhat confusing to me how the speed limit will be 70 mph, but then, for no apparent reason, drops to 55! Then back up to 70...but then it goes to 60 or 65...then back up to 70...!

It's like playing a giant game of Speed Limit Pinball! And for the life of me, I really don't see any discernible difference in the road conditions, so I can't figure out why the changes in speed limit.

Just how are speed limits determined? Here's the answer directly from a pamphlet from the North Carolina Department of Transportation:

How are speed limits determined?

Roadways are initially designed to accommodate certain speeds. If a speed limit change is requested on a State Highway System road, a traffic engineer will perform an engineering and traffic investigation to determine the appropriate speed limit. These investigations examine:

Road surface characteristics, shoulder conditions, roadway alignment and sight distance.

Commercial and residential development, and roadside friction (number of driveways, parking, pedestrians, etc.).

    Safe speed for curves and other locations along the section of road being studied.

    Frequency and severity of crashes.

    85th percentile speed — the speed at or below which 85 percent of the traffic is moving.

So there you have it! I'll certainly keep this in mind the next time I'm traveling on highway 74. And when I get to that area where the speed limit drops 15 mph from 70 to 55...it will continue to drive me crazy!

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