IMO! CFI! (Part 2)

After introducing you to the concept of a Continuous Flow Intersection (CFI) during Part 1, I wanted to continue the discussion on this new concept in traffic engineering.
For what it’s worth, here is my own opinion of this particular intersection.

An intersection designed to reduce delays and congestion, regardless of the design, can only be truly effective if the signal timings are working appropriately, which I see as being a potential challenge with the varying traffic volumes during different times of day and the current and expected commercial development growth in the area. If the signal timing is not set up properly, extra and unnecessary stops, delays, congestion, fuel consumption, driver irritation etc., are forced on the intersection. So I say, good luck to the agency in charge, you are going to need it.

In my opinion, driving through the intersection was interesting, to say the least. For someone that knew what to look for it drove okay, a little confusing, but manageable. The problem is, only a small percentage of the people traveling through that intersection have any knowledge of a CFI and how to navigate through one. As an engineer (and as a traffic superhero, of course), I believe we have a responsibility to the public to eliminate as much confusion on the roadway as possible (and therefore increase safety). If this CFI was the only way to effectively reduce the congestion, delays, emissions, etc., then fine, but it sure seems like the same thing could have been achieved through more traditional methods that would not surprise drivers as they approached the intersection.

That being said, in time regular travelers through the intersection will get used to this concept and there will be less overall confusion. Until then, drivers will continue to miss the left turn lanes located in advance of the main intersection, arrive at the main intersection, and be faced with “no left turn” signs. At which point, they hopefully will recover from the surprise quickly and continue up the road, turn around and come back to make the much less confusing right turn. Unfortunately I witnessed several drivers that made the illegal left turn at the main intersection, not to mention the three other maneuvers I witnessed left turners make only to be faced with on-coming traffic forcing them to back up. I think larger signs identifying the early left turn bays would have been advantageous in reducing confusion. I realize that the signs are hung on mast arms, and those mast arms can only support so much, but spending the extra money for larger poles would have seen exponential returns in the eyes of the driver.

The right turn lanes that direct right turning traffic off of S.R. 741 onto Austin Boulevard past the left turn crossover point is a great addition, if not a necessary component to the intersection. The traffic signals at the merge point of the right turn lane back onto Austin Boulevard, however, are not. This merge point could have been easily designed and constructed so to look and feel like you are driving on an interstate onramp, minus the high speeds, and therefore could have been controlled with a yield sign instead of a signal. After all, the point of the CFI is to reduce delays, and what better way to do that than not stop vehicles? Like I said, I am sure everything was done for a reason, so let’s assume it is necessary to stop traffic at these locations. Due to the acute angle of the intersection, Intelight traffic signals should have been used. The Intelight signals operate much like the 3M optically programmable signal heads do, but the difference is that Intelights are currently being manufactured and the 3M lights are not.

The acute angle of the merge allows for drivers traveling in the through lanes of Austin Boulevard to see very clearly the traffic light. When the light is green, this doesn’t cause a problem; however, when the light is yellow and red, a driver’s first reaction is to brake (which unfortunately I witnessed a driver come to a complete stop, not just touch the brakes) until they realize the light isn’t directed towards them. Unnecessary braking in through lanes is nothing but bad news. Again, the extra cost of the Intelight signal heads would have been worth it.

This is not the only issue regarding the signals at these right turn lanes: the phasing of the signals seems to not quite be right. The traffic that would be merging onto Austin Boulevard is being stopped when there is no legal possible way that there could be conflicting traffic on that portion of Austin Boulevard, but that’s an easy fix.

The left turn lanes on Austin Boulevard have two signalized intersections they must go through before reaching S.R. 741. The design is apparently set up so that once the first light turns green, the second will be green by the time the que reaches it. However, the timing appears to be off by a couple of seconds which therefore causes the front of the que to slow or come to a complete stop before proceeding onto S.R. 741, which greatly decreases the efficiency of the intersection. Again, an easy fix.

If I remember correctly, the entire intersection is being operated from one controller. That is pretty cool considering how many different intersecting locations and signals there are. However, less is not always more. For example, the intersection appeared to be operating off of one signal timing scheme no matter what time of day. Speaking from very limited experience during a morning off peak time, the left turning traffic does not need to be stopped for 90 plus seconds to wait for through traffic on Austin Boulevard that isn’t there. Implementing supplementary timing schemes for off peak periods or days would be very beneficial in improving the overall efficiency of the intersection as well.

And for the sake of time, I won’t get into the incorrect markings and signs being used, or the non ADA compliant pedestrian facilities. I just hope that a person with a visual impairment or in a wheel chair doesn’t try to use this intersection, because the current set up could end in a disaster.

Many of these issues can be fixed with the equipment that is already installed at the intersection. Those that can’t hopefully will not cause the problems I fear they may. The fact is though, that the intersection has been fully operational for several months now and if experience tells us anything, unfortunately the intersection will most likely remain the way it is now for years to come. In any case, I am anxiously awaiting the opportunity to view the intersection during a peak period, but until then I am glad that we have such an innovative design in our area and hope that it works as well as planned and drivers quickly adapt to the new concept. If you have any experience, opinions, thoughts, etc. about the CIF, I would love to hear them.