Innovative Intersections and Interchanges
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What Is A QR?
- Intersection design with one main intersection and two secondary intersections that are linked by a connector road in any quadrant of the intersection
- Left-turn vehicles from all four legs of the main intersection use the secondary intersections and connector road, instead of the main intersection, to complete left-turn movements
- Secondary intersections are typically signalized but can also be unsignalized
- When all three intersections are signalized, traffic signals are timed to operate together
When Should It Be Considered?
- At locations with an existing roadway that can be used as the connector roadway
- At intersections:
- With four legs
- With heavy through and left-turn traffic volumes on the major and side streets
Benefits
- Improved safety: Reduces and spreads out the number of points where vehicles may cross paths
- Increased efficiency: Rerouting left turns allows for fewer traffic signal phases at the main intersection, which means less time waiting for through and right-turn vehicles.
- Better synchronization: Synchronization of three signalized intersections improves corridor travel times on both the major and side streets
How to Navigate
Below is how to navigate a QR intersection. Click the image to view a larger version or watch the video.
Conflict Points
The number of conflict points (locations where vehicle travel paths intersect) is one metric that can be used to evaluate the safety of an innovative intersection or interchange.
There are three categories: crossing, merging or diverging.
In general, merging and diverging conflict points — where vehicles are moving in the same direction — are associated with less severe crash types than crossing conflict points where vehicles are moving in opposite directions.
The diagrams below compare possible vehicle travel movements and associated conflict points locations at a conventional four-leg intersection to a QR.
These diagrams represent a general case, with one travel lane in each direction, and do not take into account pedestrian or bicycle movements at an intersection or interchange.
When compared to a conventional four-leg intersection, the three intersections that make up a QR have, in total, two additional merging and two additional diverging conflict points, but six fewer crossing conflict points.
Conventional Intersection: Conflict Points
QR: Conflict Points
