Introduction
A Single-Point Urban Interchange, or SPUI (pronounced “spoo-ee”), is a type of interchange designed to move large amounts of traffic safely and efficiently in a small area. Utah uses SPUIs on some of its busiest roads, including I-15, to help manage freeway and cross-street traffic at one central point.
How a SPUI Works
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One Central Traffic Signal – Instead of multiple sets of lights, a SPUI has one large intersection controlled by a single traffic signal at the center of the interchange.
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Left Turns Pass Side by Side – Vehicles making left turns from opposite directions can turn at the same time, passing each other in the middle of the intersection.
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Efficient Flow – The design reduces the number of conflict points (where cars could crash) and moves more vehicles through in less time.
Key Features for Drivers
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Wider Intersection: The central crossing area is larger than a normal intersection.
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Overhead Signs and Signals: Clear signs and traffic lights guide drivers on when and where to move.
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Pedestrian Crossings: Crosswalks are located outside the interchange area for safety.
Driving Through a SPUI
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Approaching the Interchange – Watch for lane signs early and choose the correct lane (straight, left, or right).
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At the Signal – Obey the single set of lights in the middle of the interchange.
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Making a Left Turn – Follow your signal and turn left through the center, passing by oncoming left-turn traffic.
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Merging Onto Freeway – Use acceleration lanes and merge carefully, just like a standard on-ramp.
Advantages of SPUIs
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Moves more traffic in less space.
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Reduces congestion during rush hour.
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Fewer conflict points compared to traditional interchanges.
Common Mistakes to Avoid
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Not choosing the correct lane before entering.
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Hesitating or stopping in the middle of the interchange.
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Confusing the single large signal with multiple smaller ones.
Why It Matters
SPUIs are becoming more common in Utah as traffic increases. New drivers must understand how they work to avoid confusion and keep traffic moving smoothly.
✅ Takeaway: A Single-Point Urban Interchange uses one central signal to control all traffic movements. Stay alert, pick your lane early, and follow the signal to move safely through the interchange.