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PART 5
Detailed Two-Lane Roundabout:
Golden, CO PHB
Introduction The "Flashing Yellow" is followed by a "Solid Yellow" pro-
viding additional emphasis on the need to reduce speed and
This section describes analysis results of data collected be prepared to stop. "Solid Yellow" then changes to "Solid
at the northern crosswalk of the two-lane roundabout in Red." The law requires that drivers come to a complete stop
Golden at the intersection of Golden Road and Johnson Road when seeing a "Solid Red" signal indication. When approach-
(Exhibit 45). The analysis focus will be on pedestrian-related ing drivers see the "Solid Red," sighted pedestrians see the
measures, including the availability and utilization of yield and customary "Walk" signal and may begin to cross. Visually
gaps as well as pedestrian delay and O&M interventions. The impaired pedestrians hear a speech message saying, "Walk
measures are defined in the methodology chapter of this report. Signal On." After a few seconds, the vehicle display will switch
Because of the two-lane approaches at this site, the docu- to a "Flashing Red" indication for the driver, as two red lights
ment distinguishes between near-lane and far-lane effects at wig-wag back and forth. At this time drivers can proceed if
the crosswalk. These describe the vehicle state in the near and the crosswalk to their immediate front is not occupied by any
far lane relative to the position of the waiting pedestrian. pedestrians. There may still be pedestrians completing their
This section focuses on the north crosswalk with the treat- crossing when drivers see the signal turn from "Solid Red" to
ment effect of the PHB (also known as a HAWK signal). The "Flashing Red." If a pedestrian is still in the lane, a driver must
analysis presents findings in the pre and post conditions for remain stopped until the path is clear. Per proposed language
the studied crosswalk sequentially.
in the MUTCD, a driver approaching the signal during
The pre study was completed in July 2008, and a total of
"Flashing Red" must first come to a stop before proceeding
18 blind travelers participated in the pre study. The treatment
through the crosswalk. The PHB is timed to allow pedestri-
was installed following the pre study, and 13 of the original 18
ans to cross one side of the street (two lanes) at a time (entry
participants returned for the post experiment in September
or exit). Once they reach the splitter island, pedestrians will
2008, allowing approximately 60 days for driver acclimation.
place a second signal call to complete the crossing to the far-
side curb. The phasing sequence is outlined in Exhibit 47.
Pedestrian Hybrid Beacon Evaluation The PHB arrangement is intended to aid pedestrians who
desire assistance in crossing from or to the median that sep-
Pedestrian Hybrid Beacon
arates the two directions of traffic, especially when traffic is
Treatment Overview
heavy. It provides visually impaired pedestrians audible infor-
A PHB was installed at the northern crosswalk at the two- mation through an APS device about when the "Walk" sig-
lane roundabout, as shown in Exhibit 46. The treatment was nal is on.
installed at the existing crosswalk location and was outfitted
with an APS device to provide additional assistance to blind
Pretest Pedestrian Behavior
study participants.
at the PHB Crosswalk
The PHB is different from a conventional signal in that it
remains dark for traffic unless a pedestrian presses the call but- The NCHRP Project 3-78A analysis of single-lane cross-
ton. When the pedestrian presses the button, the approaching ings used a performance evaluation framework that described
drivers are given a "Flashing Yellow" indication requiring them the availability of crossing opportunities, the rate of utiliza-
to reduce speed and be prepared to stop for a pedestrian in the tion of these opportunities, and the delay and risk associated
crosswalk. with the crossings. For a single lane, the yield and gap events
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Exhibit 45. Aerial view of roundabout. Exhibit 46. Pedestrian hybrid beacon.
Photo by Lee Rodegerts
Photo by Google
4. Crossable Gap (CG): Pedestrian encounters a gap large
enough to safely cross the street without the need for a
driver yield. A crossable gap is defined as the crossing
width divided by 3.5 ft/s walking speed plus 2 s for start
time and safety buffer.
5. Non-Crossable Gap (non-CG): Pedestrian encounters
are uniquely defined by the vehicle state in the conflict lane. a gap between vehicles shorter than the crossable gap
However, at a two-lane crossing the analysis needs to con- threshold.
sider the vehicle state in both lanes. The following approach
distinguishes between driver behavior in the near lane (the The vehicle state in the far lane is defined relative to the
lane closest relative to the position of the pedestrian) and the near-lane condition in five principal categories: rolling yield,
far lane. Depending on the crossing location (entry/exit and stopped yield, crossable gap, non-crossable gap, and multiple
curb/island), the near lane can be the inside or outside lane of events. The last category indicates that more than one event
the two-lane approach. The analysis defines the vehicle state took place in the far lane during one near-lane event. For
in the near lane in five event categories: example, several cars could have gone through the far lane
during one large gap in the near lane. For multiple events, the
1. Rolling Yield (RY): Pedestrian encounters a driver who last event in the sequence is considered for analysis. Exhibit 48
has slowed down for the pedestrian, but has not come to a shows the near-lane and far-lane effects for the pre condition
full stop. at the PHB crosswalk. The near lane event outcomes are clas-
2. Stopped Yield (STY): Pedestrian encounters a driver who sified as to whether they are utilized by the pedestrians.
has come to a stop, defined as moving at a speed less than Exhibit 48 shows that from a total of 603 events, partici-
3 mph. pants encountered 194 yield events in the near lane (32.2%)
3. Forced Yield (FY): Pedestrian initiates crossing before the and did not utilize 33 rolling yields and 39 stopped yields. The
vehicle initiated the yield, but then forces the driver to corresponding overall rate of yield utilization in the near lane
slow down by entering the crosswalk. is 62.9%. A subset of these near-lane yields (15.5%) were
Exhibit 47. Phasing sequence for PHB (source: MUTCD).
