Government

Coralville pushing zipper merge at construction zones

What They're Thinking: Signs encourage drivers to 'take turns' and 'be nice'

Signs direct northbound drivers last Tuesday on Coral Ridge Avenue to take turns merging. Drivers taking turns in merging closer to the beginning of a lane closure is known as a zipper merge and can alleviate traffic backups during construction. (Liz Martin/The Gazette)
Signs direct northbound drivers last Tuesday on Coral Ridge Avenue to take turns merging. Drivers taking turns in merging closer to the beginning of a lane closure is known as a zipper merge and can alleviate traffic backups during construction. (Liz Martin/The Gazette)
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Coralville has started two major construction projects to widen and improve First Avenue and Coral Ridge Avenue — two high-traffic, north-south thoroughfares.

To keep cars flowing, the city is encouraging drivers to use a zipper merge in which drivers stay in both lanes as they approach a lane closure and then alternate, like a zipper, into the one open lane immediately before the closure.

This concept, commonly used in other states, hasn’t caught on in Iowa, where drivers tend to get into the one open lane immediately — causing backups.

The Gazette decided to ask Scott Larson, assistant city engineer, why Coralville decided to push for zippering and how the message is being received so far.

Q: Tell us about the construction projects.

A: On First Avenue we’re doing a total reconstruction from Sixth Street to Ninth Street. We’re taking it from four narrow lanes to four wider lanes, also with a center turn lane. This piece has been kind of a bottleneck for the last eight years or so. The $7.2 million project, expected to be mostly done in December, will include new east side sidewalks and improved traffic signals. Coral Ridge Avenue, known to many drivers as Highway 965, will be expanded from two to four lanes with turn lanes, a 10-foot west-side path and a pedestrian tunnel north of Oakdale Boulevard. The $8.5 million project is expected to be done in December.

Q: How did you decide to encourage zipper merging?

A: We decided that after watching how traffic was handling the lane reduction on First Avenue. As we were doing the work for temporary pavement, we had to reduce to one lane. What we were seeing in our traffic cameras was, as soon as they were turning from Highway 6, they were jamming into the left lane. At certain times of the day, we were having traffic backing up through the Highway 6 intersection. We can’t really afford for that to be gridlocked.

Q: Why do Iowans have a hard time using both lanes?

A: People don’t want to be rude, so they stay out of that right lane. Even when drivers do get in the right lane, I’ve noticed people in the right lane are extremely hesitant to get into the left lane. It kind of reminds me of when we introduced roundabouts, that you have to yield to the left. It took some time.

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Q: Have you seen the zipper merge done elsewhere?

A: I happened to vacation in South Carolina. We were driving near Charleston and I saw this sign that said ‘When busy, use both lanes.’ When I got back, we did a little research and found various web links (of videos showing the concept). It was something we really needed to try.

Q: How have you been telling the public about this?

A: We’ve posted several YouTube videos. As we started blasting this out, we were suggesting they check out this video. (Coralville also put up electronic message boards near the construction projects and posted zipper merging directions online.)

Q: What feedback have you received?

A: The main feedback is people commenting about our messages. The “take turns, be nice.” That’s one thing people have posted. I’ve seen a couple (photos) of those on Twitter. There hasn’t been any big public backlash.

Q: Is it working so far?

A: We’ve been mildly successful. First Avenue tends to get better lane usage than Coral Ridge Avenue, which is a more wide-open corridor with higher speeds coming in. We hope that message is making it to the commuters. When you get enough people doing it, then it’s not that one person over there being a jerk.

l Comments: (319) 339-3157; erin.jordan@thegazette.com

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