Questions from the May 7 flashing-yellow-arrow Webinar
OTREC researchers Chris Monsere (CM) and David Hurwitz (DH), with Stacy Shetler (SS) of Washington County, anwer questions asked during the May 7 Webinar on pedestrian safety at intersections operating the flashing yellow arrow.
Q: What degree does the FYA solve the “yellow trap” problem. And does Washington County lead the protected interval at FYA or lead/lag to benefit coordination?
A: The FYA completely solves the yellow trap problem, because now the left turn lane has its own display. There is still the potential of the “perceived yellow trap” which is when the driver in the left lane sees the adjacent through go solid yellow and thinks that the FYA is also ending. It is called perceived, because the driver should focus on their own lane’s signal control. Washington County prefers to lead the protected interval at FYA so if the protected left isn’t needed then it can be skipped. In a coordinated system we will lead or lag whichever benefits the coordination. (SS)
Q: What brand controllers do you use in Washington County? M1 by NWSS?
A: Our newer controllers are 2070’s some McCain, some Econolite, a few Peek, but brand doesn’t matter. The 2070 software is Voyage by Northwest Signal Supply. Our older controllers are 170’s running Wapiti. (SS)
Q: Have you seen a crash reduction using FYA and do you have a crash modification factor for the FYA?
A: This was not studied as part of this research. The report summarizes known CMFs from the FHWA clearinghouse. (CM)
A: Most of our conversions were from protected only to protected/permissive operation. There are CMFs relating to this situation as well as protected-permissive converted to FYA. I am not sure which situation you are asking about, but the information can be found at the CMF clearinghouse. Link here. (SS)
Q: My understanding is that you focused on intersections that had previously used protected left turns and that were converted to use FYAs. One thing I have wondered about is the effectiveness of FYAs in improving conditions for pedestrians where an existing permissive left turn is replaced by a FYA. Were any of the locations like this?
A: This was not part of the research question. We hypothesize that the driver fixation findings are not likely to vary much by display type. (CM)
A: The study didn’t look at this, but Washington County did replace some existing permissive left turns with the FYA. With the FYA as the dedicated display for the left turn, improving conditions for pedestrians can include, turning the FYA off by time of day, under heavy traffic, or when pedestrians are crossing. (SS)
Q: It sounds like all the research locations were for controlling permissive left turn traffic that is negotiating a turn across a stream of oncoming traffic. I have heard it suggested that a flashing right turn arrow could be used to caution drivers making a right turn across a crosswalk that has pedestrians crossing parallel to the vehicle phase. Have you used the flashing arrow in this way? Anything to report?
A: This is an excellent question. We have spoken with several traffic engineers who are considering this type of application. Here in Oregon, supplemental laws are unclear regarding if we can use the FYA for this application. My instinct suggests that it could result in better behavior, but to the best of our knowledge this has yet to be tried. (DH)
A: Washington County is working on using the flashing right turn arrow. We think it may caution drivers more so than a green ball. We are working out the details and will likely test it in the next month or so. (SS)
Q: Can you describe the degree of fixation or failure to fixate on peds when OTHER passive left turn indications are employed? I’m concerned that FYA is being “blamed” for general driver issues when seeking gaps in opposing traffic. If the Drivers workload for gap-finding is the issue, it may be inappropriate to focus on FYA. As ped volumes and turning and through vehicle volumes increase, we could employ the mechanisms for interrupting the FYA (or any permissive left turn indication) when a ped activates the system.
A: We have been careful to be clear that prior research has established the FYA as the best display for driver comprehension. We examined an area without much work - driver behavior with respect to pedestrian activity while making a permissive left turn. We do not imply that the FYA display is to blame. (CM)
Q: Was there any comparison to other permitted indications?
A: No, see above response (CM)
Q: What were the ages of the test driers?
A: Drivers were recruited from Corvallis, OR. From the report == “There was an over-representation of college-aged students, resulting in a relatively low average age of 25.8 years (range, 18–67 years). In total, 38 drivers participated in the test. Eight were unable to complete the test due to simulator sickness or eye-tracker calibration failures. A total of 27 subjects (14 male, 52%) completed the experiment” (CM)
Q: Have the researchers considered a near side overhead left turn signal so a driver gets left turn information sooner? (AND ALSO) Would you consider adding a near side overhead left turn signal to give motorists information before they enter the intersection?
A: We did not; hard to speculate. (CM)
Q: So realistically, are there many scenarios with enough peds to be sure drivers will take note, but not so many that permitting (rather than protecting) left turns is unsafe?
A: Our instinct is that their very well could be a threshold with enough peds that driver attention is less problematic, but permitted is still advisable. You could imagine guidance based upon ped volume and gap data. (DH)
Q: How many FYA's are deployed in WA and how many pedestrian injuries have been reported?
A: There are hundreds of FYAs in Washington County, that have been active for several years. Only 5 crashes have been reported. There is not enough historical crash data to verify a positive or negative impact, but this data does not represent and atypical frequency. (DH)
Q: With regard to the logic implemented - Was the permitted indication omitted when the ped interval(walk/dont walk) were active?
A: That is correct, in that situation the driver is presented a red arrow. (DH)
A: The permitted indication was suppressed (not displayed) when the ped interval (walk/don’t walk) were active. After the end of the don’t walk and if there was enough time, then the FYA was displayed and the peds weren’t allowed to be reserved.(SS)
Q: Did the apparently "new and improved" way of implementing a protected/permitted left turn operation, make it easier for you to consider this as an operational improvement? In other words, did you previously have reservations about the 5-section left turn protected/permitted head that were overcome by the new flashing yellow arrow option
A: All of the research conducted to date has consistently suggested that the FYA results in improved comprehension and behavior of drivers. The addition of the FYA in the 2009 MUTCD has certainly given traffic engineers improved confidence in its use, but engineering judgement is still required to determine if PPLT phasing is appropriate for a particular location. (DH)
A: The 5 section “dog house” display had the potential for the “yellow trap”. By using the FYA, we can now lead or lag the FYA to improve coordination. (SS)
Q: So what is the necessary number of driver-ped crashes at 375 treatments before the costs outweight the benefits of the reduced delay to drivers?
A: That is an important question, and we have spent a great deal of time considering it. At some point every traffic engineer has to arrive at what is, in their mind, an appropriate balance between safety and efficiency. We also think that crashes are not the only factor at play. If you are trying to promote active transportation in your community, and your pedestrians are measurable uncomfortable in your crosswalks that can impact another potentially important performance measure. (DH)
Q: Was the study intended to determine the safety and effectiveness of the FYA display versus the green ball permissive display, or did it focus on p/p versus prot-only?
A: No, see above answer
Q: Do we have hard stats on the reduction of congestion and delay? Where is said research available?
A: This was not evaluated in this study. (CM)
Q: Did the study include intersections that started with protected left arrows and followed with FYA?
A: This was a simulator-based experiment. All intersections had FYA displays, either 4 section or 3 section.
Q: it appears hat your research is more related to permtted turns (Left & Right) instead of specifically FYA. Is there a reason you only concluded results associated with FYA
A: Yes, because we only studied the FYA permissive displays. (CM)
Q: A specific but relatively rare type of intersection with permissive lefts is sometimes found with one-way streets or T-intersections. At these, drivers may see a green arrow with a WALK phase that conflicts with the turn. A green ball indication isn’t ideal, because it is associated with a straight through movement, intentionally installing a FYA that conflicts while at these intersections, vehicles cannot proceed straight ahead. Would with the WALK phase be an improvement over a green arrow that conflicts with the WALK phase?
A: If I am understanding the question correctly, and you are currently running a solid green arrow that conflicts with a pedestrian phase, a FYA would absolutely be preferable. In this case the message would be a permitted instead of a protected left, so the driver should be searching for peds in the croswalk.(DH)
A: There should never be a conflicting green arrow and walk displayed at the same time (per MUTCD). (SS)
Q: Did you consider intersection cycle length and LOS
A: Those were not factors that we considered in this experiment. (DH)
Q: would protected lagging left following the permissing flashing yellow arrow help?
A: An interesting question. In this case we only considered the behavior of the driver during the FYA, we didn’t look at the transition from or to the solid green. (DH)
