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Continuous Flow Intersection (CFI) - Prototype

My improved prototype version of the Continuous Flow Intersection (CFI) derived from in-game testing of the 'traditional' CFI. This version is built with more curvature to increase vehicle speeds. Right-turn slip lane entrances have been moved farther back from where thru-traffic has to stop, allowing more thru-traffic capacity before it starts to affect right-turn access. The prototype is also designed to handle timed traffic lights better than the traditional.

The "traditional" version is also available on my workshop for those who want more aesthetic realism.

Invented in Mexico by Fransisco D. Muir and patented in the late 80s originally as a grade-separated intersection with flyover lanes, other at-grade versions followed and the design evolved into what we know today. Also known as the "crossover displaced left-turn" (XDL or DLT), since 2000, over 40 have been built.

In conventional 4-way intersections, thru-traffic and left/right-turn traffic must stop to accommodate each other. CFIs employ dedicated lanes which distribute the load across multiple smaller intersections. Left and right turns are handled by slip lanes prior to reaching the main intersection such that the only traffic that reaches the center is thru-traffic. I like to think of it as an advanced version of your conventional 4-way with TWO-way slip lanes.

Advantages:

• Green time at the intersection is greatly increased
  
• High-capacity
  
• Constant traffic flow
  
• Around 60% fewer accidents

Disadvantages:

• Requires more land to build
  
• One of the most complex intersections to setup traffic lights for
  
• Difficult to setup when roads do not intersect at 90 degrees or where more than 2 roads intersect - In those cases, roundabouts would be better suited
  
• Higher construction and maintenance costs than a conventional intersection

Designed to be used with two 8-lane roads intersecting at 90 degree angles

I have used asymmetrical roads (4+2) and (1+2) for two reasons:

• Smoother and more compact design
  
• More imporantly, 'lane mathematics' to ensure left-turn traffic does not have to fight to merge with the straight-thru traffic of its destination road. There are 4 dedicated lanes to ensure traffic flows smoothly.
  
• Recommended for heavy traffic volumes

You do not have to use (1+2) asymmetrical roads but I've found it more effective to have DOUBLE left-turn lanes for higher capacity because the ability to handle left-turn traffic is one of the main criteria for an effective intersection.


Note: No traffic lights needed for the main intersection in the very center - Think of it as just a thru-way since thru-traffic is stopping at the internal secondary intersections where it is controlled.

Screenshot #2:
TM:PE lane connections for the internal secondary intersections

Screeshot #3:
TM:PE lane connections for the external intersections on the far ends


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