Free Daily Headlines

News

Set your text size: A A A

Ask Matt ... about newfangled interchange

Diagram shows a diverging diamond interchange. Diagram shows a diverging diamond interchange.

The Lightning's intrepid researcher answers readers' questions.

 

 

Q. I see they are starting to do some work on the intersection of I-26 and Airport Road. Is that for that new wrong-sided traffic lane project?

Correct, but "wrong-sided" is pretty harsh. Highway traffic engineers call this project a DDI (diverging diamond interchange). DDIs began in France and are slowly catching on in the US. The first DDI was built in Springfield, Mo., in 2007 but now our own highway department has several in the wings. According to Cole Hood, resident engineer for the I-26 and Airport Road (US 280) intersection project, work will be completed by fall of 2016, at a projected cost of $8.8 million. Most of the interchange falls within Buncombe County but a portion of intersection lies in the Fletcher town limits.
The cool thing about a DDI is that it maximizes the use of existing lanes and eliminates those inefficient left turn signals. I could try to explain how the Airport Road traffic crosses over to the left side of the I-26 bridge, plus all the stops and turning movements, but it is easier to watch this 3-minute YouTube video: https://www.youtube.com/watch?v=HD-0QnUlLOQ
Diverging diamond interchanges are touted to save millions of highway dollars by increasing traffic flow without adding more bridge lanes or having to build a cloverleaf. So maybe two years from now, when all the orange barrels are gone, we'll be hearing, "Look Ma, no left turn signal!"

Q. It was my understanding that the new traffic lights on Church and King streets were timed to permit traffic to flow smoothly and uninterrupted. It appears to me they are not and stopping along these routes is commonplace. Can you confirm?

Church and King Streets are both state roads (U.S. 25) and those traffic signals are not maintained by the city of Hendersonville, so I had to ask my friends at NCDOT. It appears that historical information on the project was not readily available but their records showed that the signals were timed in September of 2011. State traffic technicians, however, have made subsequent adjustments based on equipment failures or field observations. For more information contact Scott Cook, Division 14 traffic engineer, at (828) 631-1150.
The one-way pair carries traffic for nine city blocks between Seventh Avenue and Kanuga Road/Caswell Street. Traffic counts for King Street are 12,000 vehicles per day; for reasons unknown, Church Street carries 1,000 more.

Contact Matt Matteson at askmattm@gmail.com.