Paul from Aurora writes, “What's driving you crazy? HELP! Please explain the confusing lane setup at Quincy and Gun Club Road. What were they thinking? Left turns now cross oncoming traffic. Seems like a lot of confusion with the new north & southbound left turn lanes.”
This is a new to Colorado type of intersection that many drivers have not experienced yet. It is called a partial continuous flow intersection (CFI). There are several of these unique intersections in Colorado. The first one built in Colorado was in 2014 as part of a project at the U.S. 160/550 west intersection near Durango. There are a couple others including in Loveland and Colorado Springs. More are planned around the state including on Wadsworth at 38th and 44th Avenue. and on Santa Fe at Highlands Ranch Parkway.
Professional Engineer Kevin Knudsen with Dewberry design builders company describes a continuous flow intersection in their descriptive YouTube video this way: “Basically, it takes the left-turn traffic movements that are in a normal intersection and puts them at preceding intersections to the main intersection. You actually come up on the intersection, you actually cross over the main-line opposing traffic about 1,000 feet before you get to the regular intersection. Both of those do that, so when you get to the intersection, you have through traffic on the inside lanes, but your left turns, instead of opposing traffic, they're actually on the outside so they don't oppose the other traffic coming through. You basically are taking those left turn lanes and moving them to preceding intersections, which gives you a lot more green time for your main intersection. Left turn movements don't conflict with the through movements, and they can all go at the same time, and it increases the volume of the intersection dramatically."
Raymond Lee, Senior Project Manager at Dewberry, said the primary purpose of the CFI is to relieve congestion.
"The CFI can do that by just having a regular, at-grade intersection, rather than a grade-separated interchange," he said.
Even though it seems to some drivers that a CFI is more dangerous than a regular intersection, Knudsen said CFIs are actually very safe.
“They actually reduce the number of conflict points at the intersection, which reduces the potential for crashes," Knudsen said. "You don't have left turns turning across traffic. So, the intersection itself will be fairly safe. The road will be a lot safer because you'll be spreading out the amount of traffic that's on a two-lane road onto a six-lane road, which will create bigger gaps and more separation in between all the vehicles.”
Knudsen and Lee said this is just one of the many different innovations and techniques that have come up in the traffic field and they predict that we'll see more and more of these innovative intersections in the future.
If you would like to see pictures, diagrams and videos of how the CFI is supposed to work, its website is devoted to educating people about continuous flow intersections.
For more information about the CFI interchange as well as the diverging diamond interchange in Colorado Springs, check out this article.