User:Hoskir/Revision Request 4292
REPLACE EPG 902.23.5 and remove the flashing image from 902.23.4 (also update this file to outdated in the EPG - 902.5.29 Flashing Yellow Arrow brochure.pdf
902.23.5 Guidelines for Use of the Flashing Yellow Left Arrow (FYA)
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Support. This subarticle is a starting point for installations and other steps needed to successfully implement the flashing yellow arrow (FYA) for left turns at signalized intersections. The flashing yellow arrow has replaced the circular green ball for the permissive movement for left turns.
Standard. The turning movement for FYA operation must have a separate signal head. Shared indications are not allowed.
Support. Verify the installation of a stacked 4-section head is possible at a location with an existing 5- or 3-section head. If the turn head has a circular green being shared as the 2nd through indication, then a dedicated signal head will be needed for the 2nd through. Check field wiring to ensure there are enough dedicated conductors to drive the new signal heads. More conductors will be needed for a FYA head than a 5-section head, since each indication must be driven from the cabinet and not jumpered off the adjacent through.
Standard. A LEFT TURN YIELD ON FLASHING YELLOW ARROW (R10-12a) sign shall be mounted adjacent to the head.
When a new signal is being built or where an existing signal is being reconstructed, the FYA shall be used for the permissive left turn movement. All new cabinets shall be configured for FYA operation on all left turns.
Support. Verify the sign can be installed. Any existing left turn sign will need to be removed.
902.23.5.1 Installation Strategy and Guidelines
Guidance. Carefully considering where to first install the FYA can help with public acceptance. The Left Turn Phasing Warrants (safety and capacity) worksheet should be help determine what type of left turn signal phasing should be used.
The FYA will likely require a 16-position backpanel at locations with any current or anticipated signalized pedestrian control and/or dedicated overlaps, where pedestrian channels are put in the last 4 channels. However, the FYA components, if not immediately used, should be deactivated for future use.
Support. Run “Left Turn Phasing warrants” worksheet for safety and capacity warrants. Volume. Collect volume data for each approach where the FYA will be installed. This includes at a minimum, the proposed left turn movement and opposing through volumes during times where phasing may possibly change.
For each FYA approach, enter the relevant data into the “Left Turn Phasing” worksheet to determine 24 hour-by-hour what phasing option can be used. Follow recommended phasing choice for each hour.
If on an approach the number of “protected-only” hours in a day are numerous, then consideration to full-time “protected-only” phasing should be given.
902.23.5.1.1 Removing Protected-Only Turn Phasing: When Not To
Standard. Protected-only left turn phasing shall not be removed if opposing sight distance is inadequate for permissive left turns, operating speed is too great, or there are too many opposing through lanes. The Left Turn Safety Warrants still apply.
Guidance. If the approach passes Left Turn Safety Warrants, exercise engineering judgment before going from protected-only to FYA protected-permissive. Consider whether the protected-only left turn was installed for other safety reasons (crash prevention when under less restrictive phasing), before operating a possible FYA installation protected-permissive.
902.23.5.1.2 Installation – Best Candidates
Guidance. When considering locations for initial installation look for:
- a) Isolated signals OR
- b) Adjacent signals within a coordinated signal corridor within common political boundaries (minimum two signals) AND
- c) One of the following conditions for each of the signals:
- Mainline left turn approach(es) that currently operate protected/permissive.
- Mainline permissive-only left turn approach(es) having the capability to run part-time protected/permissive or protected-only.
Upgrading sidestreet approaches as well at these chosen signals is preferred.
Additional installations could also include:
- Adjacent signals to first installation and possibly across another political boundary
- Another corridor in another political entity well away from other upgraded locations
- Nearby coordinated corridor with heavy protected-permissive left turn phasing
902.23.5.2 Equipment for Reconstructed Signals
Support.
- Cabinet. Examine the existing cabinet to determine how many load switch bays are unused and how many pedestrian load switches are in operation. Each FYA approach will require either one open load switch OR one in-use pedestrian load switch (to utilize the unused yellow channel) in addition to the current load switch for a protected permissive turn.
- Cabinet Modification. Contact the cabinet vendor to provide red-lined cabinet prints that will show the needed changes. Once installation is completed, acquire 4 clean prints that reflect the final modifications.
- Controller. Controller must be capable of FYA operation. Some controllers are too old to be upgraded to FYA operation. If utilizing an existing controller, check with controller’s vendor for capability.
- Conflict Monitor. FYA operation requires a special conflict monitor. Check with signal equipment vendors for applicable models. Consider purchasing backup conflict monitors so if the installed model fails, an applicable conflict monitor is immediately available.
902.23.5.3 Equipment for New Construction
Support.
- Cabinet. Develop plans with the ultimate number of FYA approaches accounted for. Install the cabinet with an appropriate number of load switches configured for full implementation of both left turn and right turn FYA. This may require a 16-position backpanel for locations with pedestrians and overlap movements.
- Controller and Conflict Monitor. Regardless if Sec 1092 requires FYA logic, including a footnote on the D-37C sheet to reinforce FYA logic is necessary for new controllers and conflict monitors.
- Signal Heads. Make sure FYA indications are noted on the intersection plan sheet and quantity included on D-37A sheet for those approaches where FYA will be installed on the project.
Support.
- Other Plan Items. On D37-D sheet, include notation on which indications are to be wired to FYA outputs. On D38-A sheet, make sure the FYA indications are included in the Phasing Sequence chart.
902.23.5.4 Signal Hardware Purchases (Internal Retrofit)
Support. If the decision has been made to upgrade an existing signal by MoDOT forces, then plenty of lead time must be given to have all of the needed equipment on hand and ready to install. The district might elect to utilize a private contractor to do all or some of the retrofit. Purchasing of the equipment and/or contractor services will be done through General Services with detailed information given on the following items:
| St. Louis District contract submittal example |
- Quantity of items
- Traffic Control Plan
- Cabinet print numbers
- Specify Commission furnished vs. contractor furnished items clearly (if any)
- Completion date
- Specific days and times of installation allowed due to local traffic conditions
- Disposition of removed equipment
- Signing
For a district’s first installation, it is advisable to acquire the upgraded controller and monitor a few weeks in advance of the installation date so in-depth bench testing can be done by all interested parties.
902.23.5.5 Regional Cooperation
Support. Installation of the FYA at another agency’s signals might not be possible. One of the critical requirements of this option is that each lane on the approach have its own signal head. The left turn signal head cannot be sharing its circular indications with the adjacent through lanes. If an agency does not use this type of control, they cannot use the FYA. If the adjacent agency’s signals are using positive lane control, then cooperation in the form of simultaneous FYA installations can be explored.