Frequently Asked Questions regarding CFI
Continuous Flow Intersections
Continuous Flow Intersections are a new style of intersection, developed in Mexico. In the U.S., CFIs have been implemented in Louisiana, Maryland, Utah, Missouri, and New York.
What is a CFI?
How is this better than a traditional intersection?
How does this look and work?
Why does a CFI work better at Randall and
Algonquin?
There are a large number of signalized intersections
associated with this design, what happens if power goes out at this intersection?
Quotes and Statistics
Who do I contact for more information?
Additional Information
http://www.fhwa.dot.gov/publications/publicroads/09julaug/04.cfm
http://www.fhwa.dot.gov/publications/research/safety/08071/08071.pdf
http://attap.umd.edu/bbs/data/publications/Seonyeong_IEEE08_1.pdf
What is a CFI?
A continuous flow intersection has traffic turning left placed to the
left of oncoming traffic, opposite where it is normally. This removes
the conflict between on-coming traffic and traffic turning left. Vehicles
turning left access the lane a few hundred feet in front of the intersection.
How is this better than a traditional intersection?
Since left-turning traffic doesn't have to cross on-coming traffic, using
this type of intersection will increase the amount of "green" time
on the main-line route. At the intersection at Baton Rouge, Louisiana,
wait time was reduced from four minutes to less than a minute. This
type of intersection provides a comparable level of vehicle flow as
that on an interstate at a fraction of the cost, and is a dramatic
improvement over conventional intersections.
How does this look and work?
The attached animations should give a general idea of the difference
between a traditional and continuous flow intersection, as well as
how vehicles making left turns would travel:
- Traditional intersection (24.5 Mb)
- Continuous flow intersection (21.2 Mb)
- Making a left at a CFI (14.1 Mb)
Why does a CFI work better at Randall and Algonquin?
Under No Action conditions, the intersection of Randall Road and Algonquin
Road does not accommodate the projected 2030 peak hour volumes and
results in a failing level of service (LOS). As a result, a conventional
signalized intersection (with dual-left turns) and a continuous flow
intersection were studied for their ability to accommodate the projected
2030 peak hour volumes. Both types of intersection configurations studied
(continuous flow, conventional intersection) will provide the necessary
capacity to accommodate the projected 2030 peak hour volumes. However,
the conventional intersection would operate at LOS F during peak
hours and vehicles would experience an average delay of almost two minutes
(93 seconds); whereas the continuous flow intersection would
operate at LOS D during peak hours and vehicles would experience less
than one minute of delay (51.1 seconds). The latter configuration with the lesser delay
would accommodate future traffic volumes along Randall Road.
Since the Randall Road and Algonquin Road Intersection is a major intersection along the Randall Road corridor, it is important to ensure that the improvements at this intersection improve operations of the intersection and throughout the transportation network. Under No Action conditions, the total network delay along Randall Road between County Line Road and Ackman Road is over 16 minutes per vehicle. That means that the average driver will be delayed for 16 minutes while traveling from one end of the corridor to the other. In comparison, the conventional signalized intersection reduces this delay to approximately 3.3 minutes per vehicle and the continuous flow intersection reduces this delay to as little as 2.3 minutes per vehicle.
The implementation of a continuous flow intersection at the intersection of Randall Road and Algonquin Road results in operational improvements to the intersection as well as relief to the entire network from County Line Road to Ackman Road. The continuous flow intersection operates with less delay and shorter queue lengths than a conventional signalized intersection. Reduced vehicular delay is associated with reduced fuel consumption and fewer vehicle emissions. In addition, there are fewer conflict points with a continuous flow intersection than a conventional signal intersection.
There are a large number of signalized intersections associated
with this design, what happens if power goes out at this intersection?
There are a large number of signals proposed with a CFI in addition to
several conflicting routes; any loss of electrical power has the potential
to cause serious problems at the intersection. A backup system will be
introduced at the intersection such as a generator or battery-powered
light emitting diode heads.
The CFI is working great, so well that the Utah Department of Transportation (UDOT) is building 4 more this year (2010).
from Dave Thompson, Avenue Consultants, Utah, February 2010The Bangerter Highway Intersection area experienced the most crashes along the 3500 South corridor. The CFI significantly improved the intersection operation with a new innovative concept while reducing crashes.
from David Thompson, Avenue Consultants, February 2010- CFI was implemented after traffic was estimated to increase by 31 percent by 2030 (http://dot.utah.gov/main/f?p=100:pg:0::::V,T:,2007)
Prior to constructing the CFI, drivers waited through several cycle lengths during peak hours. Once complete, traffic operations noticeably improved.
from Dave Thompson, Avenue Consultants, Utah, February 2010Never thought it would work, but I was wrong, works beautifully. Keep up the good work!!
Following one week of use, virtually 100 percent of daily drivers expressed positive comments about the design. (http://www.cenews.com/magazine-article-cenews.com-august-2009-interest_grows_in_continuous_flow_intersections-7611.html)We have been overwhelmingly happy with how it’s run, and the flow has minimized backups that were pretty significant prior to making this move
said David Buck, a spokesman for Maryland Highway Administration.We were expecting some initial confusion, but it went away fairly quickly,
Eggleston said (Resident Engineer, Natchez, Mississippi).At first I was concerned that there would be a long learning curve for it, but from what I saw this afternoon, I was pleased.
(http://www.natchezdemocrat.com/news/2009/dec/04/continuous-flow-intersection-opens/)- For more information visit ABMB website – http://www.abmb.com/cfi.html
Who do I contact for more information?
For questions related to the information presented, contact the McHenry
County Division of Transportation:
Wally Dittrich
McHenry County Division of Transportation
16111 Nelson Road
Woodstock, IL 60098
Phone: 815.334.4980
Fax: 815.334.4989.