Crazy is a gift.
What causes traffic congestion on off ramp intersections?
You said cars. And you’re right. There are too many cars in large cities that use the freeway to get to the places they want to go. Cars get on and off the freeway using ramps that are controlled by traffic lights. Most of these lights are timed, do not take into account traffic trending and fail to use AI algorithms or even microwave sensors that detect how much traffic is waiting in any given lane. So too many cars is certainly a big part of the problem.
But that’s the easy answer. One of the best solutions to keep congestion from occurring at freeway on ramps and off ramps is how many traffic lights there are in close proximity of the intersections that connect to these off-ramps.
The most effective solution would be to place traffic light directed intersections as far away from the off ramp as possible. But since these intersections have been historically placed very close to the freeway off-ramps, physically demolishing and then reconstructing the traffic grid at a distance that would be conducive to mitigating congestion would take a lot of time and money.
Has anyone ever tried something different?
The answer to that question is: yes. Does it work? Depends on who you ask. At the intersection of Hillfield Road and Main Street in Layton, Utah a solution has been implemented. The efficacy of the solution is debatable, and you’ll get a different answer for every person that you ask. A UDOT engineer decided that instead of moving the roads farther away from the freeway, is to make the current roads longer. Not physically longer, mind you…just a longer pathway so more cars can be packed in the que. They did this by eliminating any and all left-handed turns at the intersection that is fed by the I-15 off ramp, and creating dedicated u-turn lanes in every direction of the intersection for people who need to make left-handed turns at an off ramp intersection farther away from the off ramp itself by making a driver go through the intersection, driving down the road for a few hundred yards and placing them in a dedicated U-Turn lane that returns the driver the intersection where they would have normally made a left-turn, and now can make a right turn because they are traveling in the opposite direction.
Here is a video I created to explain how it works. UDOT says this design is about 2 minutes faster (a reduction from 18 minutes to 16 minutes) and commuters have benefited from the improved “length of road” that was conjured through some paint…and claim that the 4 extra stop lights (required to safely facilitate the solution) on top of the 8 lights that we’re already there saves 2 minutes.
I am going to show you what it takes to shave 120 seconds off of your drive time while waiting at stop lights every 300 yards.
I am not necessarily a proponent of this solution, but I stand in awe and am amazed at what it took to get something like this approved, funded and fielded, and I would have loved to have been at the final engineering review board for this project just to see the faces of those who attended.
Also published on Medium.