Locations of full and half Continous Flow Intersections

[Ian]

The US 130/NJ 168 intersection in Collingswood, NJ appears to be a CFI.

[Alps]

The US 130/NJ 168 intersection in Collingswood, NJ appears to be a CFI.

The earliest design I know of that would qualify, certainly predating any attempt to copyright the design. If I were to design a CFI, I would not pay royalties to the copyright holders and use this as evidence to dispute.

[NE2]

I think the patent expired a few years back - and it appears to have applied only where the turn lanes are grade separated: http://www.google.com/patents/US5049000

Someone else tried to patent a standard spread-out directional interchange like at I-94 and M-10 in Detroit: http://www.google.com/patents/US3107590

There are a bunch of interesting designs in the related patents.

[kphoger]

I'm feeling too lazy to look for more.  This is just the most recent one I've looked at:

Saltillo, Coahuila
http://g.co/maps/tzcz7

OK, scratch that.  It looks like that whole corridor is being upgraded to a freeway, and that intersection in particular is now home to a stacked interchange.

[route56]

http://maps.google.com/?ll=39.013732,-95.744659&spn=0.006861,0.009645&t=k&z=17

SW 29th and Fairlawn in Topeka: A combination Half-CFI and a Diamond interchange with I-470. The ramps to and from the southeast end at Fairlawn, the ramps to and from the northwest terminate at 29th. The signals at each end of the CFI connector also serve as the signals from WB 470 to Fairlawn and from 29th to WB 470. The ramp from Fairlawn to EB 470 is unsignalized.

[kphoger]

http://maps.google.com/?ll=39.013732,-95.744659&spn=0.006861,0.009645&t=k&z=17

SW 29th and Fairlawn in Topeka: A combination Half-CFI and a Diamond interchange with I-470. The ramps to and from the southeast end at Fairlawn, the ramps to and from the northwest terminate at 29th. The signals at each end of the CFI connector also serve as the signals from WB 470 to Fairlawn and from 29th to WB 470. The ramp from Fairlawn to EB 470 is unsignalized.

I don't see how that's like a CFI at all.  Am I missing something?

[route56]

I don't see how that's like a CFI at all.  Am I missing something?

A CFI moves left turning traffic away from the main intersection. In the case of 29th and Fairlawn, the movement affected is Northbound Fairlawn to Westbound 29th. Since the connecting roadway is aligned with the ramps to and from Westbound I-470, it also eliminates a weaving move for traffic from NB Fairlawn to WB I-470.

[roadfro]

I don't see how that's like a CFI at all.  Am I missing something?

A CFI moves left turning traffic away from the main intersection. In the case of 29th and Fairlawn, the movement affected is Northbound Fairlawn to Westbound 29th. Since the connecting roadway is aligned with the ramps to and from Westbound I-470, it also eliminates a weaving move for traffic from NB Fairlawn to WB I-470.

The main aspect of the CFI intersection is that there is the one big intersection with left turns split out and separated from the main middle of the intersection, and that such left turns are spaced and signal timed in such a way that once the left turns make the crossover they don't stop at all in the intersection. The above example doesn't follow that at all...it's essentially a split diamond interchange with one two-way connector road in between (instead of two one-way connectors) located adjacent to the intersection of the two cross streets creating the split diamond.

[mcdonaat]

I'd like to add the intersection of US 65/84 and US 61 in Natchez (the eastern terminus of US 65). It looks to be at least a partial CFI.

[route56]

The main aspect of the CFI intersection is that there is the one big intersection with left turns split out and separated from the main middle of the intersection, and that such left turns are spaced and signal timed in such a way that once the left turns make the crossover they don't stop at all in the intersection. The above example doesn't follow that at all...it's essentially a split diamond interchange with one two-way connector road in between (instead of two one-way connectors) located adjacent to the intersection of the two cross streets creating the split diamond.

However, if you take the interchange ramps out of the picture, the intersection would function the same way as Revive 755's Wood River example.

If, however, having left turns being separated from the main intersection via a connector road disqualifies an intersection as being a CFI, than the Wood River and Bloomington examples would have to be thrown out.

[2Co5_14]

The US 130/NJ 168 intersection in Collingswood, NJ appears to be a CFI.

This location looks more like the CFI's cousin: the "parallel flow intersection". 

See http://www.paraflow.info/ for a video with more info.

I don't believe there are any recently built examples of the parallel flow, although the consultant who has a patent on it is trying to promote its use.  The main difference between the two types is that in a parallel flow the left turns cross over after the intersection, while in a CFI the left turns cross over before the intersection.  It seem to me that the CFI would tend to operate more efficiently than the parallel flow, since thru traffic only has to pass 2 signals, whereas it has to pass 3 signals in a parallel flow.  The more signals traffic has to pass through, the more difficult it is to properly coordinate them.

The FHWA document on alternative intersections has a more in-depth discussion on both types: http://www.fhwa.dot.gov/publications/research/safety/09060/09060.pdf

[kphoger]

The US 130/NJ 168 intersection in Collingswood, NJ appears to be a CFI.

This location looks more like the CFI's cousin: the "parallel flow intersection". 

See http://www.paraflow.info/ for a video with more info.

I don't believe there are any recently built examples of the parallel flow, although the consultant who has a patent on it is trying to promote its use.  The main difference between the two types is that in a parallel flow the left turns cross over after the intersection, while in a CFI the left turns cross over before the intersection.  It seem to me that the CFI would tend to operate more efficiently than the parallel flow, since thru traffic only has to pass 2 signals, whereas it has to pass 3 signals in a parallel flow.  The more signals traffic has to pass through, the more difficult it is to properly coordinate them.

The FHWA document on alternative intersections has a more in-depth discussion on both types: http://www.fhwa.dot.gov/publications/research/safety/09060/09060.pdf

Interesting!  I had not heard of parallel flow yet.  This gives me something to chew on.