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Chapter 2. State of Knowledge and Practice with Channelized Right-Turn Lanes This chapter presents the results of a review of completed and ongoing research related to the design and safety of channelized right-turn lanes, and summarizes the results of a survey of highway agency experience with channelized right-turn lanes. Literature Review 2.1 A literature review was conducted to update the information presented in a recent synthesis on channelized right turns (3) that was prepared in NCHRP Project 3-72, Lane Widths, Channelized Right Turns, and Right-Turn Deceleration Lanes in Urban and Suburban Areas. This section summarizes current knowledge concerning the traffic safety performance of channelized right turns and presents information obtained from the literature review of both NCHRP Project 3-72 and the current research. Safety for motor vehicles, pedestrians, and bicycles are addressed separately. 2.1.1 Motor Vehicle Safety at Channelized Right-Turn Lanes It is generally accepted that channelized right turns improve safety for motor vehicles at intersections where they are used, but there has been only limited quantitative data to demonstrate this. The research findings that are available are summarized below. Dixon et al. (4) analyzed the crash history at 17 signalized intersections with various right- turn treatments in Cobb County, Georgia, to identify the effects of those right-turn treatments on right-turn crashes. The intersections were located on both major and minor arterials. A total of 70 right-turn movements were identified for evaluation, and 57 of these movements had one of the following five common right-turn treatments: ⢠Shared right-turn lane, no island, merge, and no additional control ⢠Exclusive right-turn lane, no island, merge, and no additional control ⢠Exclusive right-turn lane, raised island, acceleration lane, and no additional control ⢠Exclusive right-turn lane, raised island, merge, and yield control ⢠Shared right-turn lane, raised island, large turning radius, merge, and yield control Table 1 summarizes the number of right-turn crashes for each treatment. The analysis was based strictly upon crash frequencies over a 2-year period and did not include exposure data related to traffic volumes. 5
Dixon et al. (4) noted the following general findings, indicating that they merit future research: ⢠The use of a traffic island appears to reduce the number of right-angle crashes ⢠The addition of an exclusive right-turn lane appears to correspond to elevated sideswipe crashes ⢠The addition of an exclusive lane on the cross street for right-turning vehicles (i.e., an acceleration lane) does not appear to reduce the number of rear-end crashes when no additional control is implemented Table 1. Comparison of Crash History for Common Right-Turn Treatments (4) Treatment Shared right-turn lane, merge, no island, no additional control Exclusive right- turn lane, merge, no island, no additional control Exclusive right- turn lane, acceleration lane, raised island, no additional control Exclusive right- turn lane, merge, raised island, yield control Shared right-turn lane, large turning radius, merge, raised island, yield control Number of sites evaluated 29 8 5 7 8 Number of right turn crashes for 2-year period 18 13 14 22 10 Average number of right turn crashes per site per year 0.31 0.81 1.40 1.57 0.63 Crash type Percent of Right-Turn Crashes Observed Right angle 50 31 22 23 0 Rear-end 28 23 64 59 90 Sideswipe 17 31 7 18 0 Other 5 15 7 0 10 The Texas Department of Transportation sponsored a study (5) similar to that performed by Dixon (4). In the Texas study, crash data for six intersections were reviewed. A total of 30 approaches with one of the following treatments were evaluated: ⢠Right-turn lane with lane lines ⢠Right-turn lane with raised island ⢠Shared through-right lane ⢠Shared through right lane with raised island Table 2 summarizes the number of right-turn crashes for each treatment over a 3-year period. The values do not include consideration of right-turn volume; however, they can provide an appreciation of the variability in the number of right-turn crashes among the different treatments. 6
Table 2. Annual Right-Turn Crashes by Type of Right-Turn Treatment (5) Intersection Total Treatment RTL w/island RTL w/striping Shared lane Shared lane w/island Number of approaches 30 14 6 8 2 Number of crashes 16 9 2 1 4 TxDOT projectâAverage number of right -turn crashes per site per year 0.18 0.21 0.11 0.04 0.67 Dixon projectâaverage number of right-turn crashes per site per year N/A 1.57 0.81 0.31 0.63 RTL = right-turn lane; SL = shared through-right lane. The majority of the crashes (10 out of 16) were rear-end crashes. Of the 10 rear-end crashes, 5 crashes occurred in a right-turn lane with a raised island. As shown in Table 2, the shared-lane configuration experienced the lowest average number of right-turn crashes per site per year. The right-turn lane separated by a raised island showed the highest number of crashes in Dixonâs study and the second highest number of crashes in the TxDOT study. Staplin et al. (6) conducted an accident analysis to examine the problems that older drivers have in intersection areas. Approximately 700 accident records were reviewed during the analysis. In general, older drivers had difficulty yielding the right-of-way and making left turns at intersections, but the accident analysis did not reveal channelized right turns as a safety issue for older drivers. Tarawneh and McCoy (7) conducted field investigations to study the effects of the geometrics of right-turn lanes on the turning performance of drivers. Right-turn performance of 100 subjects was evaluated at four signalized intersections of different right-turn lane channelization and skew. Three of the four intersections had a channelized right-turn lane. The investigation found that drivers turn right at speeds 5 to 8 km/h (4 to 5 mph) higher on intersection approaches with channelized right-turn lanes than they do on approaches with unchannelized right-turn lanes. In addition, it was observed that drivers are less likely to come to a complete stop before turning onto the cross street on approaches with channelized right turns. However, no explicit safety findings were inferred from this result. McCoy et al. (8) conducted field studies on rural two-lane highways and found a higher incidence of merging conflicts from vehicles entering the cross street from a channelized right turn without an acceleration lane than those with an acceleration lane. McCoy et al. (8) developed guidelines for channelized right-turn lanes at unsignalized intersections on rural two-lane highways. In developing the guidelines, McCoy et al. evaluated the safety effects of channelized right-turn lanes based on accident data, field studies, and computer simulation of truck dynamics. An analysis of the accident history at 89 rural intersections with and without channelized right-turn lanes over a 5-year period found no effect of channelized right-turn lanes on the frequency, severity, or types of accidents that occur on approaches to unsignalized intersections. Thus, it was concluded from the accident analysis that channelized right-turn lanes do not provide the road user with any safety benefits or disbenefits. Field studies which investigated the tendency of drivers to travel faster than the design speed of 7
the channelized roadway and to over steer at some point through the turn found that some drivers exceeded the design speeds of the channelized right-turn roadways, but they seldom exceeded the margin of safety for their vehicles. Vehicle-path data showed that nearly all of the vehicles observed were well-positioned in the lane at the center of the curve, indicating that they were able to follow the curvature of the channelized roadway with ease. Results from the truck simulation study support the use of the AASHTO criteria for curves on open highways, instead of the AASHTO criteria for minimum-radii intersection curves for the design of intersection curves on rural highways with substantial truck volumes. Results of the truck simulation also showed that the margin of safety between the maximum safe speed for trucks and the design speed is narrow. In a 2006 study by Abdel-Aty and Nawathe (9), artificial neural networks were used to analyze the safety of signalized intersections. Geometry, traffic, and crash data were obtained for 1,562 signalized intersections from six counties in Florida. Neural network trees were used to determine the relationship between intersection geometry/configuration and the frequency of specific types of crashes. The study found that: ⢠The presence of channelized right-turn lanes on the major road was shown to have no significant effect on total crashes, but was linked to an increase in turning and sideswipe crashes. ⢠On the minor road, the presence of channelized right-turn lanes was associated with a decrease in total crashes and an increase in rear-end crashes. 2.1.2 Pedestrian Safety at Channelized Right-Turn Lanes No studies have been found that have used crash data to document the pedestrian safety implications of channelized right-turn lanes. Prior crash studies have focused on the vehicle- pedestrian collisions involving turning vehicles, but the geometrics of the intersection were not available to document the type of turning lane present. A five-state analysis of more than 5,000 vehicle-pedestrian collisions found that 38 percent of all such crashes occurred at intersections (10). Further examination of the intersection accidents found that 30 percent of these crashes involved a turning vehicle. There was no further breakdown to determine if the vehicle was turning right or left. From a query of a North Carolina database that includes detailed crash types developed with the Pedestrian and Bicycle Crash Analysis Tool, one can determine the breakdown of turning vehicles (11, 12). The North Carolina system includes 5 years of data (over 11,000 pedestrian-motor vehicle collisions). Intersection crashes account for 26 percent of those collisions. Left-turning vehicles accounted for 10 percent of the collisions at intersections, while right-turning vehicles accounted for 6 percent. Statistics gathered by the Oregon DOT (13) show that 19 percent of vehicle-pedestrian crashes occurring at intersections arose from drivers making right turns. The geometry of channelized right-turn lanes permits turns at higher speeds than in an unchannelized situation. Higher motor-vehicle speeds represent higher risk to pedestrians crossing the roadway. Research by Zegeer et al. (14) has established that, in the event that there 8
is a collision, vehicle speed directly affects the likelihood that a pedestrian will be fatally injured. Should a pedestrian be hit by a vehicle traveling at 32 km/h (20 mph), the chance of being killed is 5 percent. For a 48-km/h (30-mph) vehicle, that likelihood of a fatality rises to 45 percent, while for vehicles traveling at 64 km/h (40 mph), the likelihood of a fatal injury is 85 percent. Motorists traveling at higher speeds have less time to see pedestrians and require more time to slow, stop, or change direction to avoid striking them. Geruschat and Hassan (15) evaluated driversâ behavior in yielding the right-of-way to sighted and blind pedestrians who stood at three different positions relative to the curb at the crosswalk at entry and exit lanes at two different roundabouts. The researchers found that a driverâs willingness to yield to a pedestrian was related to the speed of the vehicle. Specifically, at low speeds [less than 24 km/h (15 mi/h)], drivers yielded approximately 75 percent of the time, whereas at higher speeds [greater than 32 km/h (20 mi/h)], they typically yielded less than 50 percent of the time. Safety for Pedestrians with Special Needs Other crash-based analyses have focused on pedestrians with special needs, particularly the elderly. One such study that looked specifically at the types of crashes occurring at intersections showed older pedestrians to be overrepresented in collisions with both left- and right-turn collisions (16). Collisions involving left-turning and right-turning vehicles accounted for 17 percent and 13 percent, respectively, of all intersection accidents involving pedestrians. Pedestrians who were age 75 or older and were involved in a vehicle-pedestrian collision were struck by a left-turning vehicle in 24 percent of cases and by a right-turning vehicle 14 percent of cases. Those aged 65 to 74 were struck by a left-turning vehicle in 18 percent of cases and by a right-turning vehicle in 19 percent of cases. Schroeder et al. (17) conducted a paired comparison study of blind and sighted pedestrians at three channelized right-turn locations. At each location, pedestrians were observed as they assessed gaps in traffic and identified opportunities to cross the channelized right-turn roadway. A key issue in the study was whether the geometry of channelized right-turn lanes and/or the lack of signal control at channelized right-turn roadways negatively affect the delay and safety for blind pedestrians. Blind pedestrians rely on auditory cues when crossing the roadway because they cannot use visual information to identify approaching vehicles and assess appropriate gaps in traffic. However, at channelized right-turn roadways, blind pedestrians have to judge traffic moving in a circular path while dealing with a significant amount of background noise from traffic at the intersection. The objectives of the study were to: ⢠Identify difficulties experienced by blind pedestrians in crossing a channelized right-turn lane safely. ⢠Test the effect of crosswalk location, geometry of the channelized right-turn lane, and traffic volumes on pedestrian delay and risk performance measures. Study participants consisted of nine blind and nine sighted pedestrians, who were tested in pairs (one blind and one sighted). The pedestrians were asked to stand by the roadside as though 9
they were going to cross and indicate when they felt it was safe to cross. No actual crossings were performed in the study. The blind pedestrians signaled when they would cross by pushing a button and holding it down as long as they felt it was safe to cross. The participants released the button when they no longer felt it was safe to cross. The sighted pedestrians gave similar indications by raising and lowering a white pocket folder they held in their hand. Key findings in the research were: ⢠On average, blind pedestrians require more time to make a crossing decision. The greater time consists of longer lead and lag times. ⢠Blind pedestrians make a greater percentage of risky âgoâ decisions and a greater percentage of unnecessary âno goâ decisions than sighted pedestrians. ⢠The percentage of risky âgoâ decisions tends to increase with higher conflicting vehicle volumes in the turn lane, while the percentage of unnecessary âno goâ decisions tends to decrease at high volumes. ⢠Background traffic volumes had similar effects for sighted pedestrians. This may suggest that the ânoiseâ of background traffic, which complicated the decision process for blind pedestrians, may be partially offset by the uncertainty of sighted pedestrians in knowing whether vehicles upstream of the turn lane were entering the channelized right-turn lane or continuing straight through the intersection. The effect of background volume on blind pedestrian performance was not significant. ⢠The comparison of crossing performance at two crosswalk locations (in the center vs. downstream of the channelized right-turn lane) showed no significant effect for either group of pedestrians. The center crossing location appeared to result in slightly better performance in terms of reducing risky and unnecessary decisions, but additional data are necessary to show significance. Pedestrian Safety at Roundabouts The geometry of roundabouts is similar to channelized right-turn lanes in some respects, and roundabouts and channelized right-turn lanes pose similar challenges to pedestrians with vision impairment attempting to cross the road. In both situations, the pedestrian with vision impairment has to judge traffic moving on a circular path and the vehicle movement is not controlled by signals. In both cases, traffic may be free-flowing or may yield to other vehicles (e.g., at the downstream end of the channelized right-turn roadway or roundabout approach). The pedestrian with vision impairment is faced with the task of identifying gaps in traffic, distinguishing between sounds from traffic in the turn lane and background traffic noise at the intersection, and judging yield behavior of drivers. Researchers from Western Michigan University and Vanderbilt University recently conducted a series of studies of blind pedestrians crossing at roundabouts (18, 19). One study evaluated the crossing behavior of blind and sighted pedestrians at three roundabouts in the Baltimore, Maryland, metropolitan area (18). The research evaluated how well each pedestrian group judged whether gaps in traffic were long enough to safely cross to the 10
splitter island. Using six blind and six sighted participants that each had experience maneuvering urban environments and roundabouts, the study found that the blind pedestrians were nearly 2.5 times less likely to make correct judgments than sighted pedestrians, took longer to detect crossable gaps, and were more likely to miss crossable gaps altogether. Results were found to be most significant at high-volume intersections. A follow-up study was conducted at three different roundabouts to determine if the presence of visible indicators of a blind pedestrian (e.g., guide dog or long cane) would produce better yielding patterns from drivers. At each location, pedestrians holding long canes elicited more yielding maneuvers. Also, drivers were more likely to yield at the entry of a roundabout than at the exit. Another study evaluated pedestrian crossings at a double-lane urban roundabout in Nashville, Tennessee (19). Participants included six blind and six sighted pedestrians. Each pedestrian participated in two sessions; each session consisted of six trials. On three trials, pedestrians crossed the roadway independently, followed by a certified orientation and mobility (O&M) specialist. On the other three trials, they used a hand signal to indicate when they would have started crossing, but did not actually cross the roadway. The research found that: ⢠Blind pedestrians waited three times longer to cross than sighted pedestrians. ⢠Nearly 6 percent of the crossing attempts by blind pedestrians were judged dangerous enough to require intervention. ⢠In high-volume conditions, blind pedestrians waited almost twice as long to make a crossing than in low-volume conditions; traffic volumes had much less of an effect on the wait time of sighted pedestrians. ⢠Sighted pedestrians made the crossing 41 percent of the time without waiting for any approaching vehicles to pass the location. In contrast, only 15 percent of crossings by blind pedestrians were made before a vehicle passed; with most participants waiting for a period of time that allowed five or six vehicles to pass before crossing. ⢠Drivers yielded frequently on the entry lanes but not the exit lanes. ⢠Sighted pedestrians were much more inclined to accept a driverâs yield than a blind pedestrian. In post-session interviews, blind participants indicated that they would likely take measures to avoid crossing the roundabout test site on a daily basis due to the significant number of self- initiated and experimenter-initiated interventions from potential vehicle-pedestrian conflicts. While these studies focused on roundabouts, the free-flow conditions of vehicles entering a roundabout are very similar to those of a channelized right-turn lane and, therefore, the findings may potentially be applicable to channelized right-turn lanes. In a recent study, Inman et al. (20) tested the ability of an audible surface treatment (similar to a rumble strip) to improve pedestrian safety at crosswalks upstream of roundabouts. Using a controlled environment, the research team documented the reactions of seven pedestrians with vision impairment to vehicles approaching an intersection with and without the proposed treatment. In two lanes of traffic, test vehicles approached an intersection where pedestrians were waiting for audible cues to signal their approach and yield. In order to simulate a real-world 11
situation of pedestrians encountering an innovative treatment, study participants were not provided any specific information on the treatment prior to the study. The treatment layout consisted of four sound strips upstream of the crosswalk that would be activated by all vehicles and then two more strips at the crosswalk that would only be traversed by non-yielding vehicles. Based on hand gestures from the pedestrians, the research team documented the number of times each pedestrian correctly detected a yielded vehicle, the number of false detections, and the number of missed vehicles. Results of the study found that, after the surface treatment was added, detection accuracy improved by an average of approximately 58 percent. There were also a substantial number of false detections, which would have resulted in pedestrians crossing in an environment that they believed was protected by stopped vehicles but that would have, in fact, been vulnerable to approaching vehicles. The authors suggest, however, that the treatment may be more effective in single-lane approach situations where one lane of traffic would not create the false security for both lanes. Pedestrian Research in NCHRP Project 3-78A The effects of channelized right-turn lanes on pedestrians with vision impairment were studied as part of NCHRP Project 3-78A, Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities (21). The objectives of the research were to assess pedestrians with vision impairment crossing a channelized right-turn lane and evaluate treatment installations to assist those pedestrians in crossing. The study site for NCHRP Project 3-78A was located in Charlotte, North Carolina, and consisted of channelized right-turn lanes on all four intersection approaches. Data were collected at two of the four turn lanes, as indicated in Figure 2. Each turn lane has a deceleration lane on the approach, but does not have an acceleration lane for vehicles to merge onto the cross street. A pedestrian crosswalk is located at the center of each island, perpendicular to the sidewalk. Safety improvement treatments were installed at the channelized right-turn lanes during Summer 2008: ⢠Sound stripsâdevices intended to provide audible cues to pedestrians with vision impairment about approaching vehicles ⢠Sound strips in combination with pedestrian-actuated beacons The sound strips, spaced approximately 9-m (30-ft) apart, were installed on each of the deceleration lanes. The sound strips were a modification of a treatment used in recent FHWA research at roundabouts (20), with minor modifications in treatment placement. The pedestrian- actuated beacon was installed, in conjunction with an audible indication that the beacon was flashing, at one of the crosswalks. Lane delineators were also installed as part of the treatment to prevent last-minute entry by vehicles into the deceleration lane. 12
Pedestrians with vision impairment participated in both the pre-treatment and post-treatment phases of the study. During the study, participants were asked to navigate across the channelized right-turn lane to the best of their ability using the existing cues provided at the crosswalk. In the event that a participant moved into an unsafe situation, research team members were available to intervene. During the pre-treatment data collection, observations of the research team included: ⢠The channelized right-turn lane study site experienced high traffic volumes. ⢠Pedestrian delays were relatively high. ⢠Gap acceptance and yield utilization were relatively low. ⢠Experimenter interventions were in the range of 8 to 10 percent, with several other âself- interventionsâ by the participants. Figure 2. Channelized Right-Turn Lane Study Location for NCHRP Project 3-78A (21) Post-treatment data collection was conducted to determine if sound strips, either alone or in combination with pedestrian-actuated beacons, have any effect on yield behavior of drivers or on risky crossings (i.e., interventions) by pedestrians with vision impairment. Analysis of post- treatment data suggested the following: 13
⢠Yield rates of drivers increased slightly (from 15.2 to 22.0 percent) where sound strips were installed in combination with flashing beacons. There was no change where sound strips were installed as the only treatment. ⢠Installation of treatments reduced, but did not eliminate, interventions. ⢠Several participants noted that they could hear better to make crossing decisions from the curb than from the island. They stated that the sound of traffic behind them, when waiting on the island, made the crossing decision more difficult. 2.1.3 Bicycle Safety at Channelized Right-Turn Lanes There is an inherent risk to bicyclists at channelized right turns because motor vehicles entering the channelized right-turn roadway must weave across the path of bicycles traveling straight through the intersection. However, no studies based on crash history are available to support this presumption. Furthermore, a similar conflict between through bicyclists and right- turning vehicles is present at all intersections, except at intersections where right turns are prohibited or three-leg intersections where there is no leg to the right on a given approach. There are also no studies that provided data on the risk of collisions between motor vehicles and bicycles on the channelized right-turn roadway itself or at the point at which the channelized right-turn roadway joins the cross street. The following discussion presents basic statistics on bicycle safety, followed by available information on bicycle-related safety issues at right-turn lanes. In 2002, 662 bicyclists were killed and an additional 48,000 were injured in traffic accidents in the U.S. (22). Thus, bicyclists accounted for about 2 percent of all traffic fatalities. Bicyclists accounted for approximately 12 percent of all nonmotorized traffic fatalities, while pedestrians accounted for 86 percent; the remaining 2 percent were skateboard riders, roller skaters, etc. Oregon reports that most bicycle crashes (65 to 85 percent) do not involve collisions with motor vehicles but rather involve falls or collisions with stationary objects, other bicyclists, and pedestrians. Of the bicycle/motor vehicle crashes, 45 percent occurred at intersections (13). In another evaluation of bicycle/motor vehicle crashes, Tan reported that approximately 5 percent of bicycle/motor vehicle crashes occurred when a motorist made a right turn (23), but no information was provided on whether the respective crashes occurred at intersections with channelized right turns. Tan also reported that approximately 4 percent of bicycle/motor vehicle crashes occurred at an intersection controlled by a signal at which the motorist struck the bicyclist while making a right-turn-on-red. Clark and Tracy (24) reported that 13 percent of all bicycle/motor vehicle crashes resulted when motorists were making a right-turn movement, and a majority of these crashes involved a straight-through bicyclist being struck by a right-turning motor vehicle. Clark and Tracy indicated that many bicyclists find changing lanes difficult or choose to ignore signage and pavement markings. Much of the advice for highway designers in dealing with intersections and right-turn lanes is applicable only to locations where bicycle lanes already exist (or are planned in the future). As 14
indicated in Chapter 3, the MUTCD (25) and AASHTO bicycle guide (25) recommend breaking bicycle lane markings ahead of the intersection and then marking the bicycle lane again at the intersection itself, to the left of the right-turn lane. This positions bicyclists traveling straight through the intersection away from any conflict with right-turning vehicles and allows a merge area for right-turning vehicles to get into right-turn lane. Two recently completed studies for the FHWA have included observational studies of bicyclists and motorists as they maneuvered through a variety of right-turn lane configurations (27, 28). One of the studies was a before-after effort in which the conflict zone, defined as the place where the paths of bicyclists and motorists crossed most often, was treated with blue pavement markings at 10 intersections in Portland, Oregon (27). Figure 3 illustrates the use of blue pavement markings at the entrance to and exit from a channelized right-turn lane. Figure 3. Blue Pavement Marking Treatment at Channelized Right-turn Lane (27) a. At entrance to channelized right-turn roadway b. At exit of channelized right-turn roadway 15
Configurations addressed in the Oregon blue bike lane program included exit ramps, right- turn lanes, and entrance ramps. The markings were also supplemented with unique signs showing the blue markings and yield signs for motorists (see Figure 4). Both video observations and survey feedback were collected as part of the study, with approximately 850 bicyclists and 190 motorists in the before period and 1,020 bicyclists and 300 motorists in the after period. The most important results were as follows: ⢠There was a significant increase in motorists yielding to bicyclists after the treatment was installed, from 71 percent in the before period to 87 percent in the after period. ⢠Significantly more bicyclists followed the path marked for bicyclists after the blue markings were in place, 85 percent in the before period compared to 93 percent in the after period. ⢠There was a decrease in head-turning and scanning on the part of bicyclists after the treatment was installed, from 43 percent in the before period to 26 percent in the after period, which was a concern. The authors were not sure of the reason for this result. ⢠While conflicts between the two modes were rare, the conflict rate decreased from 0.95 conflicts per 100 entering bicyclists in the before period to 0.59 conflicts per 100 entering bicyclists in the after period. ⢠The survey data showed that 70 percent of the motorists noticed the blue markings, and 59 percent noticed the accompanying sign. When asked about safety, 49 percent of the motorists thought it would increase safety, 20 percent thought it would be the same, 12 percent thought it would be less safe, and the remaining motorists were not sure. ⢠The bicyclists surveyed thought the treatment would increase safety (76 percent). Only 1 percent thought it would decrease safety. Overall, it was found that the treatment resulted in a safer riding environment and a heightened awareness on the part of both bicyclists and motorists. The City of Portland continues to use this treatment at 6 of the 10 locations today. The second study examined the behaviors of bicyclists and motorists at a âcombinedâ bicycle lane/right-turn lane used in Eugene, Oregon (28). The results were compared to observations made at a more traditional right-turn lane. The combined lane created a 1.5-m (5-ft) bike pocket within a 3.6-m (12-ft) right-turn lane, leaving 2.1 m (7 ft) for right-turning vehicles (see Figure 5). The traditional lane location used for comparison was a 3.6-m (12-ft) right-turn lane and a 1.5-m (5-ft) bike pocket (see Figure 6). Approximately 600 bicyclists were videotaped at each location as they approached and continued straight through the intersection. The differences in the two types of right-turn lanes can be summarized as follows: ⢠Bicyclists and motorists tended to queue up behind one another more often in the combined lane facility (43 percent of the time) than in the standard lane facility (1 percent of the time). ⢠At both locations, bicyclists were most often able to position themselves in the bike pocket (94 percent of the time in the combined lane and 86 percent of the time in the standard lane). At the combined lane intersection, bicyclists tended to use the adjacent 16
through lane more often (2 percent of the time) compared to virtually no such positioning at the standard lane. This was primarily due to the occasional bus that needed to turn right at the combined lane intersection, which then forced the approaching bicyclists to use the through lane. ⢠At both locations, the yielding behavior of each mode was captured. At the combined lane location, the motorist yielded to the bicyclist in 93 percent of the cases where the two parties would have collided had someone not slowed or stopped. At the standard lane location, motorist yield 48 percent of the time. This low percentage of yielding by motorists at the standard lane is believed to be an artifact of bicyclists having to shift to the left on the approach to the intersection in order to move from the bicycle lane adjacent to the curb to the bike pocket at the intersection. ⢠No conflicts requiring either mode to suddenly stop or change direction were observed at either location. Figure 4. Signs Used in Oregon Blue Bike Lane Program (27) 17
Figure 5. Combined Bicycle Lane/Right-Turn Lane (27) Figure 6. Traditional Bike Lane/Right-Turn Lane (28) In addition to the observational data, a brief survey of a sample of bicyclists was administered at both locations. When asked to compare the two locations, 18 percent said the combined lane was safer, 27 percent said it was less safe, and 55 percent said there was no difference. Overall, the observational and survey data showed the combined bicycle lane/right- 1 ft = 0.305 m 1 ft = 0.305 m 18
turn lane to be an effective treatment that could be beneficial at locations where right-of-way constraints exist. There has also been a perception study conducted for FHWA in which participants were asked to view a number of right-turn lane configurations and provide a rating of how comfortable they would be interacting with right-turning traffic in an effort to continue straight through the intersection (29). The configurations rated included: ⢠A standard right/through lane in which the bicyclist could travel straight on the approach and continue through the intersection. ⢠An auxiliary right-turn only lane that was added at the intersection, which allowed the bicyclist to travel straight on the approach and forced the motorist to cross the path of the bicyclist. ⢠A travel lane that became a right-turn lane at the intersection, forcing bicyclists to shift left across the path of motorists in order to continue straight through the intersection. ⢠A gradual increase in pavement width on the intersection approach that became a right- turn lane at the intersection, also forcing bicyclists to shift left across the path of motorists in order to continue straight through the intersection. A regression model was developed using the perception ratings as the dependent variable and several geometric and operational variables as independent measures. The most significant predictors of the a bicyclistâs comfort level were whether there was a bike lane present on the approach and whether the bicyclist had to shift to the left across the motorist path in order to continue through the intersection. The presence of a bike lane increased the comfort level, while the requirement to shift across the motoristâs path decreased the comfort level. This result confirmed some of the observational data collected in the combined bicycle/right-turn lane study previously described. An example of a treatment for bicycle lanes at intersections that is considered inappropriate suggests channeling bicyclists onto a sidewalk or bike path and having them behave as pedestrians (24). Crash records suggest this approach is seriously flawed, especially since it can encourage wrong-way riding. On streets with bicycle lanes, the current recommended designs ensure straight-though bicyclists are positioned to the left of exclusive right-turn lanes. On streets without bicycle lanes, bicyclists and motorists must perform the same maneuvers as if separate lanes were marked. They must do so, however, without the guidance offered by the bicycle lane markings and without the same amount of space available to share the road at the intersection. In both instances, there are several important design features to remember (24): ⢠As the length of the right-turn lane increases, so does the exposure of the bicyclist to traffic driving on either side of them. In addition, the speed of vehicles in the right-turn lane may be greater. Thus, exclusive right-turn lanes should be kept as short as possible. 19
⢠As both bicyclists and motorists pass through intersections, they are concentrating on their own position on the road and on traffic within the intersection. No driveways should be positioned near the intersection to cause additional conflicts. Highway Agency Experience 2.2 A formal highway agency survey on channelized right-turn lanes was conducted as part of NCHRP Project 3-72, the results of which were reflected in the Synthesis on Channelized Right Turns (3) that was also developed as part of that research. Therefore, no formal survey was needed as part of the current research. However, because the survey was conducted in 2003, there was a clear need to update the results. To assure that any new research, design practice, or agency experiences were identified, the research team asked the AASHTO Standing Committee on Highway Traffic Safety (SCOHTS) to send an email through their list-serve to all 50 state highway agencies asking for new or updated information on channelized right-turn lanes. The following seven states responded to the request for information: Idaho, New York, Rhode Island, Tennessee, Texas, Virginia, and West Virginia. This section presents key findings from both research projectsâNCHRP Project 3-72 and the current researchârelated to highway agency practice with channelized right-turn lanes and focuses on geometric design issues, traffic control, and pedestrian considerations at channelized right-turn lanes. 2.2.1 Geometric Design Issues at Channelized Right-Turn Lanes The highway agency survey (3) conducted in NCHRP Project 3-72 indicated that 87 percent of state and local highway agencies use channelized right turns; all seven highway agencies that provided additional information in the current research indicated that they utilize channelized right-turn lanes. Even casual observation suggests that channelized right-turn lanes are a relatively common geometric feature at intersections on urban and suburban arterials. Deceleration Lanes Right-turn deceleration lanes serve one or more of the following functions (30): ⢠A means for safe deceleration outside the high-speed through lanes for right-turning traffic. ⢠A storage area for right-turning vehicles to assist in optimization of traffic signal phasing. ⢠A means for separating right-turning vehicles from other traffic at stop-controlled intersection approaches. The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. In response to the survey (3) conducted in NCHRP Project 3-72, 89 percent of the state 20
highway agencies and 70 percent of the local agencies that use channelized right-turn lanes indicated that they have used deceleration lanes in advance of those channelized right-turn lanes for at least some locations. Acceleration Lanes Acceleration lanes provide an opportunity for vehicles to complete the right-turn maneuver unimpeded and then accelerate parallel to the cross-street traffic prior to merging. In response to the survey (3) conducted in NCHRP Project 3-72, 77 percent of the state highway agencies and 43 percent of the local agencies that use channelized right turns indicated that they have used acceleration lanes downstream of those channelized right turns for at least some locations. In the recent informal survey, one agency responded that acceleration lanes are generally used when the angle between turning roadway and intersecting roadway is less than 60 degrees. Crosswalks Crosswalks that are parallel to and constitute an extension of the sidewalk may provide the best alignment information for pedestrians with vision impairment because they allow the pedestrian to continue along a straight travel path. Also, the sounds of traffic moving parallel to the pedestrianâs line of travel can often be used for establishing and maintaining alignment for crossing. Although not specifically illustrated in Figure 7, an additional factor to be considered in locating the crosswalk is the ability to construct appropriate curb ramps to provide access for wheelchair users. While the alignment of parallel crosswalks may be preferred by pedestrians with vision impairment, it is difficult to build wheelchair ramps in these locations without shifting grades at the gutter that cause problems in traversing the ramps for wheelchair users. For that reason, the perpendicular crosswalk alignments would be preferred for wheelchair users, along with maintaining the crosswalk at a level grade, with a cross slope of less than 2 percent. Table 3 summarizes highway agency practices concerning the placement of crosswalks for channelized right-turn roadways (3). The most common highway agency practice is to place the crosswalk near the center of the right-turn roadway (i.e., not immediately adjacent to either of the intersecting streets). The table indicates that 77 percent of state highway agencies and 67 percent of local highway agencies that use channelized right turns have placed pedestrian crosswalks in this center position. The recent informal survey produced similar results, where six out of seven highway agencies indicated that they place the crosswalk near the middle of the right-turn roadway. 21
Figure 7. Alternative Crosswalk Locations Table 3. Locations Where Highway Agencies Place Pedestrian Crosswalks at Channelized Right-Turn Roadways (3) Location Number (percentage) of agencies State agencies Local agencies Total At the upstream end 8 (22.9) 7 (23.3) 15 (23.1) In the middle 27 (77.1) 20 (66.7) 47 (72.3) At the downstream end 9 (25.7) 12 (40.0) 21 (32.3) NOTES: 1. Columns total to more than 100 percent because of multiple responses. 2. Percentages are of those highway agencies that have used channelized right-turn roadways. The Wisconsin DOT (WisDOT) has been implementing a newer design for channelized right-turn lanes that incorporates a different shape for the islandâan isosceles triangle rather than an equilateral triangle configurationâas illustrated in Figure 8 (31). Option 1: Marked crosswalk Location: Upstream end Direction: Parallel to sidewalk Option 2: Marked crosswalk Location: Upstream end Direction: Perpendicular to sidewalk Option 3: Marked crosswalk Location: Center Direction: Perpendicular to sidewalk Option 6: No marked crosswalk Location: N / A Direction: N / A Option 5: Marked crosswalk Location: Downstream end Direction: Perpendicular to sidewalk Option 4: Marked crosswalk Location: Downstream end Direction: Parallel to sidewalk 22
Figure 8. Isosceles-Triangle Island Shape Used by WisDOT Angle of Intersection With Cross Street The survey results indicate that the alignment of a channelized right-turn lane and the angle between the channelized right-turn roadway and the cross street can be designed in two different ways: ⢠A flat-angle entry to the cross street like the channelized right-turn lanes illustrated in Figures 1 through 3 and Figure 7 ⢠A nearly-right-angle entry to the cross street like that partially visible on the right side of the photograph in Figure 8 These two designs are compared in Figure 9. The two designs shown in Figure 9 differ in the shape of the island that creates the channelized right-turn lane. The flat-angle entry design has an island that is typically shaped like an equilateral triangle (often with one curved side), while the nearly-right-angle design is typically shaped like an isosceles triangle. The flat-angle entry design is appropriate for use in channelized right-turn lanes with either yield control or no control for vehicles at the entry to the cross street. The nearly-right-angle entry design can be used with STOP sign control or traffic signal control for vehicles at the entry to the cross street; yield control can also be used with this design where the angle of entry and sight distance along the cross street are appropriate. 2.2.2 Traffic Control at Channelized Right-Turn Lanes The survey results (3) from NCHRP Project 3-72 indicate that only 14 percent of state highway agencies and 17 percent of local highway agencies have formal policies concerning traffic control devices for channelized right-turn roadways. Other agencies rely on the Manual on 23
Figure 9. Typical Channelized Right-Turn Lanes with Differing Entry Angles to the Cross Street [Adapted From (14)] Uniform Traffic Control Devices (MUTCD) (24) for guidance concerning the proper application of yield signs, stop signs, and signals; such guidance deals with the general application of these devices, but is not specific to channelized right turns. The informal survey conducted in the current research had similar results; five out of seven agencies did not have a formal policy concerning traffic control at channelized right-turn lanes. One agency stated that yield signs are the most commonly used traffic control. Another agency has a policy in which if the end of the Channelized Right-Turn Lane with Flat-Angle Entry to Cross Street Channelized Right-Turn Lane with Nearly Right-Angle Entry to Cross Street Sk et ch es b y M ic ha el K im el be rg 24
channelized right-turn lane is more than 9 m (30 ft) from the primary intersection control, it operates under its own signal, stop, or yield sign. Highway agencies were asked to identify innovative traffic control devices they have implemented at channelized right-turn roadways. Table 4 summarizes use of innovative traffic control devices by highway agencies. Between 35 and 50 percent of highway agencies have used high-visibility crosswalk markings and florescent yellow-green signs, but fewer than 10 percent of agencies have tried other innovative devices. In the recent informal survey, one agency reported using the fluorescent yellow-green signs; another has implemented flashing warning signs for motorists to warn of a pedestrian crossing. One agency uses a sign that states âTURNING TRAFFIC MUST YIELD TO PEDESTRIANS;â another agency uses imprint to help create high-visibility crosswalks. Table 4. Innovative Traffic Control Devices at Channelized Right-Turn Roadways (3) Traffic control device Number (percentage) of agencies State agencies Local agencies Total High-visibility crosswalk markings 13 (37.1) 13 (43.3) 26 (41.3) Fluorescent yellow-green signs 16 (45.7) 15 (50.0) 31 (49.2) Real-time warning devices 2 (5.7) 3 (10.0) 5 (7.9) Other dynamic message signs 2 (5.7) 2 (6.7) 4 (6.3) Other 1 (2.9) 0 (0.0) 1 (1.6) NOTES: 1. Columns total to more than 100 percent because of multiple responses. 2. Percentages are of those highway agencies that have used channelized right-turn roadways. In the survey (3) conducted in NCHRP Project 3-72, highway agencies were asked whether they install pedestrian-actuated signals at channelized right-turn roadways on urban and suburban arterials. The responses are summarized below: ⢠Of the highway agencies that use channelized right-turn roadways, only 6 percent of state highway agencies and 17 percent of local highway agencies install pedestrian- actuated signals at all channelized right-turn roadways. ⢠The majority of highway agencies using channelized right-turn roadways (83 percent of state highway agencies and 60 percent of local highway agencies) install pedestrian- actuated signals at selected locations only. ⢠Of the highway agencies that use channelized right-turn roadways, approximately 11 percent of state highway agencies and 23 percent of local highway agencies do not use pedestrian-actuated signals. In the recent informal survey, four out of the seven agencies indicated that they have installed pedestrian-actuated signals at select locations. Highway agencies were also asked whether they have developed or used any strategies specifically intended to assist pedestrians with vision impairment in crossing channelized right- turn roadways without pedestrian signals. Of the highway agencies that use channelized right- turn roadways, 23 percent of state highway agencies and 10 percent of local highway agencies 25
have either developed or used such strategies. The general types of strategies used by the responding agencies to assist pedestrians with vision impairment in crossing channelized right- turn roadways are summarized in Table 5. One highway agency that does not currently use accessible pedestrian signals at channelized right-turn lanes is considering their use. One highway agency reportedly installed audible signals at one intersection, but was requested by an organization representing pedestrians with vision impairment to deactivate the sound. In the recent informal survey, one agency reported using different curb configurations to facilitate crossing the right-turn lane. One agency uses a short crossing distance, perpendicular to the roadway, with detectable warning devices and way-finding cues within the turning roadway island. In the recent informal survey, four out of seven agencies indicated that they do not implement any strategies specifically aimed at pedestrians with vision impairment. One agency uses signs stating âTURNING TRAFFIC MUST YIELD TO PEDESTRIANS.â One agency uses different curb configurations to facilitate crossing the right-turn lane. One agency uses a short crossing distance, perpendicular to turning roadway, with detectable warning devices and way- finding cues within the turning roadway island. Table 5. General Strategies Used by Highway Agencies to Assist Pedestrians with Vision Impairment (3) General strategy State agencies Local agencies Total Curb ramps with truncated domes 5 1 6 Textured curb ramps 4 1 5 Audible signals 1 0 1 While textured curb ramps are listed by highway agencies as a strategy used to assist pedestrians with vision impairment, research has indicated that various textures are not detectable or usable by pedestrians with vision impairment. The only texture that is recognized to provide adequate detectability, both underfoot and under cane, is the truncated dome detectable warning surface required by the Americans with Disabilities Act (ADA). However, neither strategy assists pedestrians with determining the appropriate time to cross channelized right-turn roadways. 2.2.3 Pedestrian Considerations at Channelized Right-Turn Lanes In the survey conducted in NCHRP Project 3-72, highway agencies were asked about pedestrian considerations in determining the radius or width of channelized right-turn roadways. Of the highway agencies that use channelized right-turn roadways, 23 percent of state highway agencies and 40 percent of local highway agencies indicated that they consider pedestrian issues in determining the radius and/or width of a channelized right-turn roadway. On the other hand, in the informal survey of highway agencies, six of the seven agencies stated that they use design vehicles rather than pedestrian considerations to determine the radius of a channelized right-turn lane. One agency stated that pedestrians have been used in some cases as a factor in determining the radius. Table 6 presents a list of specific pedestrian-related issues considered by highway agencies in determining the radius or width of a channelized right-turn roadway. One highway 26
agency indicated that they do not use channelized right turns, and another is trying to minimize their use, because of pedestrian concerns. Table 6. Pedestrian Issues Considered in Determining the Radius or Width of Channelized Right-Turn Roadway (3) Pedestrian issue Number of agencies State agencies Local agencies Total Pedestrian crossing distance/time minimized 3 1 4 Vehicle speeds minimized 1 3 4 Provision of pedestrian refuge location 2 2 Improved sight distance of opposing traffic 1 1 Pedestrian volumes 1 1 General consideration of pedestrians 4 1 5 Highway agencies were also asked if they have encountered any safety problems related to pedestrians crossing at channelized right-turn roadways on urban and suburban arterials. Of the highway agencies that use channelized right-turn roadways, approximately 23 percent of state highway agencies and 17 percent of local highway agencies have encountered pedestrian-related safety problems at channelized right-turn roadways. Highway agencies reported the following safety concerns related to pedestrians crossing at channelized right turns: ⢠General concern about pedestrian safety at channelized right-turn roadways (5 agencies) ⢠Higher vehicle speeds put pedestrians at risk (3 agencies) ⢠Pedestrians with vision impairment may expect approaching traffic to stop (1 agency) ⢠Truck-trailer off tracking onto sidewalk jeopardizes pedestrian safety (1 agency) ⢠Drivers may not yield to pedestrians (1 agency) ⢠Larger radii may make pedestrians less visible to drivers (1 agency) ⢠There is some confusion regarding the most appropriate crossing location (1 agency) ⢠There is greater exposure to pedestrians (1 agency) ⢠Small islands and snow on islands are not conducive to pedestrian use (1 agency) Only one highway agency reported a safety problem at a specific location. One location with an unsignalized right-turn roadway and no pedestrian signal has a sight distance problem that will probably be addressed by providing a signal. In the informal survey, five out of the seven agencies reported no safety issues. Two agencies reported occasional pedestrian safety concerns. 27
