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Example Paraflow
US-23 @ Campus View Boulevard, Columbus, Ohio

Type of Paraflow >> 2-Phase / 4-Leg Partial
Total Vehicles Per Hour >> 7,893
Average Vehicle Delay Per Hour >> 18 seconds
Average Number of Vehicle Stops >> 0.42

The Ohio Department of Transportation is currently planning to construct
a trench under three intersections including Campus View (above) that is estimated to cost over $80 million.
A paraflow would cost under $20 million.

A questionnaire respondent writes, 'I think that your usage of the US-23/Campus View intersection as a potential use for this design is misleading.  Although it would solve the problem of traffic backing up on Campus View by adding additional queue length for the left-turning vehicles, it would not address the problem of northbound traffic backing up on US-23, which is exactly what the trench is designed to do.  Although the paraflow is cheaper to build, it would still leave a major design flaw in the current pattern unaddressed.'

The VISSIM simulation shown above is an accurate prediction of how the paraflow would operate using future traffic data supplied by the Ohio DOT. The reason the paraflow should work at this location is due to the simultaneous Campus View eastbound thru/left movements and Campus View westbound left turn movement (south junction).

The number of signal phases is effectively reduced with more green time for the US-23 through movements. Reducing the number of signal phases also reduces lost time due to fewer all-red phases and less start-up time. The simulation shown above accurately represents this and shows a resulting Level of Service B in the design year 2028. No traffic would therefore back up onto I-270.

- Greg
 

So, just how much time could a paraflow save? A lot!
As the figure below shows, delay at a congested signal can be reduced by over 80%.

The paraflow is a new kind of intersection...

The parallel flow intersection (or paraflow) is an innovative signalized street intersection that operates with only two or three phases per repeating signal cycle.

 

that attacks traffic congestion...

By reducing congestion at busy intersections, the paraflow can make them safer to drive, reduce travel time otherwise spent in queue, and lower vehicle emissions. Compared to an interchange, the paraflow is smaller and costs less but can still process substantial traffic volumes.

using a simple idea...

The underlying idea is simple; left turns bypass the main intersection by first turning onto a cross street frontage road. View >>

By removing left turns from the main intersection, the paraflow can operate with only two phases per cycle. Conventional traffic signals require four phases per cycle at busy intersections to provide for left turns. With only two phases, the paraflow is far more efficient.

to produce very green results.

In fact, the paraflow can operate using a 60 second cycle length with as much as 50 seconds of green time dedicated to thru movements generating potentially 10 times more capacity than an equivalently sized conventional signalized intersection.

 

For more information about the paraflow, go to the Library page where you will find reference materials, research, illustrations and simulations. Click here to go to the Library >>