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· Level of federal, state, and local support and cost sharing in were chosen for roundabout treatments in Towson, the deci-
implementing the proposed treatments; sion was made to focus on turn-lane treatments in the Char-
· Sufficient vehicle and pedestrian demand to enable a mean- lotte region. Ultimately, the intersection of Providence Road at
ingful evaluation of the treatment's impact on the system Pineville-Matthews Road was selected for treatment evaluation.
performance; The main intersection is signal controlled with an eight-
· Availability of adequate numbers of potential research par- phase actuated-coordinated signalization scheme and pro-
ticipants who are blind and are in reasonable proximity to tected dual-left turns on all four approaches. The through
the sites identified for data collection tasks; movements on Providence Road and Pineville-Matthews
· Proximity of the sites to the data collection team and to one Road have two and three lanes per direction, respectively. The
another to maximize use of limited budget resources; and site has CTLs on all four approaches, each yield controlled at
· Adequate representation of the various geometric condi- the downstream merge and with deceleration lanes present.
tions to be considered. No acceleration lanes were present on any of the approaches.
The posted speed limit on all approaches is 45 mph. Traffic
volumes were high during the peak hour periods. Land uses
Identification of Treatment Site Alternatives near the intersection include office buildings, retail strip malls,
and residential. Two of the four CTLs were selected for this
The research team used three methods to identify candi-
study. Both served the right-turn movements from Providence
date sites. First, a solicitation for sites was posted on e-mail list
Road onto Pineville-Matthews Road. Figure 5 shows the loca-
serves. Appendix D contains aerial and site photographs of the
tions of the studied crosswalks at the southeast and northwest
sites identified in the responses to the request. In the second
corner of the intersection.
method of site identification, agencies and practicing engineers
Traffic volumes (in 2005) at the tested crosswalk in the
active in the planning, design, and construction of round-
southeast corner show 24-hour turning flows of 3,200 vehicles
abouts were contacted. While roundabouts were not the only
per day (vpd) and adjacent through traffic of 12,000 vpd. The
focus of the study, it was hypothesized that CTL sites would be
downstream conflicting movement is composed of the oppos-
readily identified in proximity to (more rare) roundabout sites.
ing through traffic (10,600 vpd) and the opposing left turn
Agencies and companies contacted included Maryland State traffic (3,000 vpd). Volumes at the northwest corner crosswalk
Highway Administration; Kansas DOT; Washington State are generally higher at 6,000 vpd in the CTL, and adjacent
DOT; New York State DOT; North Carolina DOT; California through traffic of 18,400 vpd. The downstream conflicting
DOT; Florida DOT; City of Clearwater, FL; City of Kennewick, through flow was 22,400 vpd, and the opposing left turn was
WA; City of Modesto, CA; City of Bend, OR; City of Portland, 2,700 vpd. Low pedestrian activity was observed at the site,
OR; City of Tucson, AZ; City of Golden, CO; Town of Vail,
CO; MTJ Engineering; Roundabouts, USA; Ourston Round-
about Engineering; and Alternate Street Design. The team
had follow-up meetings and/or telephone conversations with
the Maryland State Highway Administration, Washington
State Department of Transportation, New York State Depart-
ment of Transportation, and Ourston Roundabout Engineer-
ing. The third method for site selection consisted of reviewing
sites studied under NCHRP Project 3-72, "Lane Widths, Chan-
nelized Right Turns, and Right-Turn Deceleration Lanes in
Urban and Suburban Areas" and NCHRP Report 572: Round-
abouts in the United States.
Photo by Google
Selection of Treatment Sites
Channelized Turn Lanes
Providence Road at Pineville-Matthews Road Charlotte,
NC. The selection of a channelized turn lane facility was tied
This figure shows an aerial photograph of the CTL treatment site at the
to the location of roundabout sites since CTL locations are intersection of Providence Road and Pineville-Matthews Road in
common to most jurisdictions. The research team considered Charlotte, NC. The studied crosswalks are highlighted and located
in the southeast and northwest corners of the intersection.
four candidate sites, two of which were located in Charlotte,
NC, and the other two in Towson, MD. Given that no sites Figure 5. Aerial view of CTL site.
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on the order of 20 pedestrians per day, primarily during the flicting) and adjacent through traffic, and (2) an audible pat-
midday off-peak period. However, all main approaches of tern that helps identify slowing or yielding vehicles.
the intersection had marked crosswalks and pedestrian sig- The flashing beacons were installed on both sides of the
nals. Drivers were therefore believed to expect (occasional) street at the SS+FB corner and had a pole-mounted dual-
pedestrian activity. In the pretest, crosswalks at the CTLs head signal display. The beacons rested in "Dark" mode
were unsignalized and outfitted with standard marking and and flashed in wig-wag patterns (a 1-s flash frequency) for
pedestrian signage. 20 s after a pedestrian pushed the button. The flashing beacon
Figure 6 shows street-level photographs of each of the was further outfitted with a push-button integrated locator
studied approaches and the installed treatment. The treat- tone and an audible speech message, "cross with caution; cars
ments were sound strips that were intended to increase may not stop," that was repeated concurrent with the flash-
the awareness of pedestrians of approaching vehicles at the ing display.
northwest corner (SS-ONLY) and sound strips in combi-
nation with a pedestrian-actuated flashing beacon that was
Single-Lane Roundabouts
intended to increase driver yielding behavior at the south-
east corner (SS+FB). Both approaches further had lane delin- The research team considered four candidate sites:
eators installed to prevent late merges into the turn lane. This the Pullen-Stinson roundabout in Raleigh, NC, the two
was necessary to ensure that the sound strips in fact picked up single-lane approaches to the Towson, MD, roundabout,
all right-turning vehicles. a single-lane roundabout located in Voorheesville, NY, and
The sound-strip treatment tested was an off-the-shelf, tem- a single-lane roundabout in Charlotte, NC. The Pullen-
porary, and self-adhesive rumble-strip material. The sound Stinson roundabout has been studied by research team mem-
strips were white in color and had a vertical elevation of 0.25 in. bers under other research grants. Based on the fact that other
The sound strips were evenly spaced over approximately 50 ft, treatments have been used and evaluated at this site, the high
and a total of 5 strips were installed at each turn lane. The first proximity of the roundabout to the campus of North Carolina
sound strip was installed at a distance of 10 ft upstream of the State University where pedestrian activity is extremely high,
crosswalk. At a constant speed of 50 ft/s (34.1mph), this cor- and the fact that other research trials as part of the NIH proj-
responds to a temporal spacing of the "clack" sounds of 1 s. ect were planned with blind participants during the project
A faster speed results in a shorter rate of clack sounds. A vehi- timeframe, the decision was made to eliminate this round-
cle that slows down while traversing the sequence of sound about for study of further treatments. However, the analysis
strips will generate an audible pattern where the rate of clack ended up including some prior data collected at the site. The
sounds decreases as the vehicle slows (longer time between Towson roundabout was intriguing; however, previous treat-
clacks). The sound strips therefore aim to accomplish two ments installed at the roundabout were removed because of
goals: (1) an audible distinction between right-turning (con- their negative effect on vehicular movements, which may be
Photo by Bastian Schroeder
Photo by Bastian Schroeder
This figure shows two photographs of the treatments installed at the CTL study site. The left photograph shows a view from the crosswalk splitter island down
the deceleration lane with the sound-strip and lane-delineator treatments. The right photograph shows the view of a driver approaching the crosswalk with the
sound strips, lane delineators, and flashing beacons installed.
Figure 6. Photo of sound strip and flashing beacon treatments.
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problematic from the standpoint of installing new treatments not to proceed with treatment installation was made after the
for evaluation. The Voorheesville roundabout was consid- pretest was completed because it was decided that project
ered problematic in terms of proximity to the research team. resources were better spent elsewhere.
Ninth Street at Davidson Street Charlotte, NC. The site Pullen Road at Stinson Drive Raleigh, NC. Although
chosen for single-lane roundabout data collection was located not officially part of the NCHRP Project 3-78A data collection
at the intersection of 9th and Davidson streets in Charlotte. effort, further analysis of an alternate single-lane roundabout
The urban roundabout site was close to the research team was conducted to test the hypothesis that pedestrian cross-
members, and the team was in contact with city personnel ing performance was affected by higher traffic volumes. The
willing and able to install the necessary treatments. The site is roundabout at the intersection of Pullen Road and Stinson
located in a primarily residential neighborhood just northeast Drive located in Raleigh was one studied previously by the
of uptown Charlotte, the city center. The inscribed diameter research team. For this research, a supplemental evaluation
of the roundabout is approximately 140 ft (42.7 m), with was performed using pre-existing video of crossing trials prior
approach speed limits of 25 mph (40 km/h). The crossing to any treatment installation and using the same experimen-
distance is approximately 16 ft (4.9 m) for each leg of the tal protocol used in NCHRP Project 3-78A.
crossing. The major approach had average annual daily traffic The roundabout is located in close proximity to the cam-
(AADT) of 9,900 vpd, which is well within the capacity limits pus of North Carolina State University and has a high volume
of a single-lane roundabout. Peak hour traffic counts showed of pedestrian traffic from students walking to and from class.
total roundabout entering volumes of 830, 530, and 780 vehi- The roundabout has an inscribed diameter of 88 ft (26.8 m)
cles per hour (vph) for a.m., lunch, and p.m. peak periods, and approach speeds of 25 mph (40 km/h). The crossing dis-
respectively. About 80% to 85% of these flows were on the tance is approximately 13 ft (4.0 m). The AADT at this site is
major approaches on Davidson Street. Volumes on 9th Street higher than at the Charlotte site at 15,000 vpd along the major
were low at or below 100 vph. The team therefore concluded approach, Pullen Road. Peak hour traffic counts showed total
to focus the study on the two approaches along Davidson roundabout entering volumes on the order of 1,300 vph for
Street. Figure 7 shows the location of the two studied cross- a.m. and lunch peaks, and 1,500 vph in the p.m. peak. About
walks, as well as a street level view of the southeast entry 90% of these flows were on the major approaches on Pullen
approach. Road. Figure 8 shows the location of the studied crosswalk, as
No posttest treatment evaluation was performed at this well as a view of the southern approach from an adjacent
single-lane roundabout. The recommendation and direction building rooftop. Since this site was originally studied under
Photo by Bastian Schroeder
Photo by Google
This figure shows two photographs of the studied single-lane roundabout at the intersection of Davidson Street and 9th Street in Charlotte, NC. The left image
shows an aerial photograph with the studied crosswalks highlighted on the southwest and northeast approaches of Davidson Street. The right image shows a
pedestrian-level photograph of the roundabout entry leg.
Figure 7. Aerial and pedestrian-level photographs of Davidson Street at 9th Street in Charlotte, NC single-
lane roundabout.
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Photo by Bastian Schroeder
Photo by Google
This figure shows two photographs of the studied single-lane roundabout at the intersection of Pullen Road and Stinson Drive in Raleigh, NC. The left image
shows an aerial photograph with the studied crosswalk highlighted on the southwest approach of Pullen Road. The right image shows a photograph of the
studied crosswalk taken from a nearby building.
Figure 8. Aerial and pedestrian-level photographs of Pullen Road at Stinson Road in Raleigh, NC single-
lane roundabout.
a different research project, no NCHRP Project 3-78A treat- The crosswalk was marked and outfitted with standard pedes-
ments were installed. trian signage. Traffic volumes on Golden Road indicated an
AADT of 15,000 vpd. Figure 9 shows the location of the studied
Golden Road at Ulysses Drive Golden, CO. One addi- crosswalk as well as a street view of the eastern approach.
tional single-lane roundabout site was studied by the research
team. This site, located in Golden, CO, was intended to pro-
vide a control condition for a nearby two-lane roundabout. Two-Lane Roundabout
The single-lane site was studied concurrently with the pretest The research team identified three candidate two-lane
and posttest treatment conditions at the two-lane site. Both roundabout sites, in Gatineau, Quebec, Canada; Towson,
roundabouts were on the same corridor (Golden Road). The MD; and Golden, CO. The Gatineau site already had a sig-
purpose of this additional analysis was to test for a learning nal installed and would have therefore prevented the team
effect in the same participants returning to the same round- from performing a pretest and posttest comparison. The
about without treatment installation. It further allowed a direct Towson site has a very good mix of pedestrian and vehicular
within-participant comparison of the single-lane and two-lane traffic, with heaviest pedestrian traffic during the middle of the
roundabout crossing ability of the same participants. day. This site also offers the advantage of providing a mix of
The roundabout has a central island diameter of 100 ft single-lane and two-lane entries/exits. However, the geometry
(30.5 m), including a truck apron of 10 ft (3.1 m). The lanes is very different from most single- or two-lane roundabouts,
at the studied crosswalk are 20 ft wide, partly to accommodate which was an important consideration in rejecting the site.
nearby roadside bus stops. The crosswalk is located approxi- Further, the local agency was only supportive of treatment
mately 60 ft (18.2 m) from the circulating lane measured at the installations short of signalization.
exit side, and approximately 50 ft (15.2 m) from the round-
about yield line at the entry. The two-stage crossing is divided Golden Road at Johnson Road Golden, CO. The two-
by a 6-ft, raised splitter island, but the crossing itself is at lane roundabout site finally selected for installation of treat-
pavement elevation. No pedestrian-detectable warning sur- ments was located in Golden. The site provided two good
faces were installed on the splitter island, so the study partic- approaches for treatment installations, and the team enjoyed
ipants were instructed by the O&M specialist when they com- significant local support for the research effort and treatment
pleted the first half of the crossing. No detectable warning installation. Figure 10 shows an aerial view of the site and the
surfaces were installed on the crosswalks at this roundabout. locations of the studied crosswalks. The PHB treatment was
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Photo by Bastian Schroeder
This figure shows two photographs of the studied single-lane roundabout at the intersection of Golden Road and Ulysses Street in Golden, CO. The left image
shows an aerial photograph with the studied crosswalks highlighted on the east approaches of Golden Road. The right image shows a pedestrian-level
photograph of the roundabout entry leg.
Figure 9. Aerial and pedestrian-level photographs of Golden Road at Ulysses Street in Golden, CO single-
lane roundabout.
installed on the northwest corner, and the raised crosswalk located approximately 30 ft (9.1 m) from the circulating lane
was installed on the southeast corner. at the northwest corner, and approximately 20 ft (6.1 m) at
The roundabout has a central island diameter of 90 ft the southeast corner. The two-stage crossings are divided by
(27.4 m), including a truck apron of 10 ft (3.1 m). The lanes 15-ft raised and landscaped splitter islands. Detectable warn-
at the studied crosswalk are 11 ft wide (3.4 m), resulting in ing surfaces were installed on the splitter islands and on the
a total crossing distance of 22 ft (6.8 m). The crosswalk is curbs at both crossings. The crosswalks were marked and out-
fitted with standard pedestrian signage. Traffic volumes on
Golden Road indicated an AADT of 15,000 vpd. Peak hour
total entering flows at the roundabout were 1,900 vph in
the a.m. peak and 2,100 vph in the p.m. peak. Traffic volumes
were highest on the two Golden Road approaches (approxi-
mately 70% to 75% of entering traffic).
Figure 11 shows a photograph of the RCW installed at
the southeast approach of the roundabout on Golden Road.
The RCW was installed at a vertical elevation of 3 in. from
pavement surface and a transitional slope of 1:15. This means
that the transition to the 3-in. elevation occurred over approx-
imately 45 in., or just short of 4 ft. This installation resulted
Photo by Google
Photo by Janet Barlow
This figure shows an aerial photograph of the two-lane roundabout
treatment site at the intersection of Golden Road and Johnson Road
in Golden, CO. The studied crosswalks are highlighted and located
This figure shows a pedestrian-view photograph of the RCW treatment
in the southeast and northwest approaches of Golden Road.
installed at the southeastern approach of the Golden Road
two-lane roundabout.
Figure 10. Aerial view of Golden Road at Johnson
Road in Golden, CO two-lane roundabout. Figure 11. Raised crosswalk treatment Golden, CO.
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Photo by Lee Rodegerts
3 seconds 3 seconds
This figure shows a pedestrian-view photograph of the PHB treatment
installed at the northwestern approach of the Golden Road two-lane
roundabout.
4 seconds
Figure 12. PHB treatment Golden, CO. 10 seconds
in a less severe impact on vehicle traffic compared to other
installations visited by the research team. Other installations
of RCWs commonly feature vertical elevations up to 5 in.
and/or transitional slopes as steep as 1:10. Clearly, the speed
reduction effect is greater with higher vertical elevation and a
steeper slope.
The RCW was intended as a temporary installation. It was 15 seconds minimum
signal rests in this phase
therefore simply installed on top of existing pavement and
This figure shows a graphic of the PHB phasing scheme. The sequence
used the existing curb and gutter system for drainage. This of vehicle/pedestrian displays is "Flashing Yellow/Don't Walk," "Steady
resulted in the RCW being sloped downward on each side. Yellow/Don't Walk," "Steady Red/Walk," "Flashing Red/Flashing Don't Walk,"
and "Dark/Don't Walk." Phase durations for these phases in sequence are
A permanent installation would likely be installed flush with 3 s, 3 s, 4 s, 10 s, and 15 s, where the last represents a minimum time for
the sidewalk and incorporate drainage into the RCW design the "Dark/Don't Walk" and the PHB rests in this phase if no further
pedestrian calls are placed.
via piping. As a result of this installation, pedestrians first
walked down the curb ramp from sidewalk level and then Figure 13. PHB phases and signal timing.
back up onto the crosswalk. Numerous participants noted
that this unexpected down/up transition was uncomfort- display changed to a "Steady Red" phase, while the pedestrian
able to walk on. The RCW installation therefore satisfied
displays showed "Walk" (4 s). The PHB then showed a "Flash-
the intended treatment effect (on traffic), but the pedestrian
ing Red" for vehicles concurrent with the pedestrian "Flash-
aspects of the design should be modified for a permanent
ing Don't Walk" (10 s). Finally, the vehicle display returned
installation. Pavement markings were as shown in Figure 11
to "Dark" and the pedestrian display to "Don't Walk." The
and emphasized the upslope of the RCW.
PHB was timed to rest in this phase for a minimum of 15 s
Figure 12 shows a photograph of the PHB installation at
before cycling back through the phases.
the northwest approach of the roundabout on Golden Road.
Expected pedestrian behavior at the PHB was as it would be
The PHB was installed on roadside poles following MUTCD
requirements for vertical height and additional signage. at a standard pedestrian signal. Pedestrians were expected to
The PHB installation featured a total of four pole-mounted push the button (since they observed a "Don't Walk" phase)
devices, with two each at the entry and exit legs. All four devices and cross during the "Walk" interval. Drivers were expected
were outfitted with push-button integrated APS devices. The to be stopped during the "Red" phase. The "Flashing Yellow"
signal timing was such that the two sides (entry and exit) oper- was intended to alert the driver of the impending signal phase
ated fully independently of each other. The vehicle display change. The "Solid Red" offered drivers dilemma-zone pro-
rested in "Dark" mode; the pedestrian display rested in "Don't tection in case they were too fast and too close to the crosswalk
Walk." The phasing sequence of the PHB after pedestrian acti- to come to a stop. Drivers were allowed to proceed with cau-
vation and the times for each phase are shown in Figure 13. tion after having stopped during the "Flashing Red" phase,
After pedestrian push-button activation, the PHB entered provided the pedestrian had cleared the crosswalk. This feature
a "Flashing Yellow" phase for vehicles (3 s), followed by a reduced the required stop time for drivers from 14 s to 4 s.
"Steady Yellow" phase (3 s). The pedestrian signal during both Appendix F gives additional details on the PHB installation,
of these phases remained as "Don't Walk." Next, the vehicle including timing parameters and signal plans.
