traditional arrow signs and markings with clarifying words (e.g., "all" and "only"); fishhook arrow signs and markings with clarifying words; and. Anticipated Benefits to Aging Road Users:Aging drivers, who as a group experience reduced head/neck mobility, should have a longer time in which to search for conflicts with through traffic before entering the destination street as the result of these design changes. There was also less yielding to crossing pedestrians on multilane approaches (43% non-yield rate) compared to single-lane approaches (17% non-yield rates). The authors concluded that the guidelines for extended receiving lane width at intersections are effective for driver safety, and improve the performance of older as well as younger drivers. Presumably, the benefit of upstream "priming" is derived from a reduction in the requirements for serial processing of concurrent information sources (sign message and signal condition) at the instant a maneuver decision must be completed and an action performed. This will help the public to understand the differences between circles and roundabouts, and will gradually reduce opposition. Prepare to stop and yield the right-of-way to . The sign components affecting detection are sign size, color, shape, brightness, and message or content design. Studies in other countries help to shed some light on the optimum design characteristics of modern roundabouts. Also, questionnaire results indicated drivers perceived that making a right turn on an approach with a channelized right-turn lanewithout an acceleration laneon the cross street was more difficult than at other locations, and even more difficult than at skewed intersections. The Traffic Engineering Handbook(TEH, 1999) states that: "Crossing roadways should intersect at 90 degrees if possible, and not less than 75 degrees." Existing 8-inch circular signal indications may be retained for the remainder of their useful service life. Flannery and Datta (1996) indicate that roundabouts are commonly used in Australia, Great Britain, France, Germany, Denmark, Ireland, Norway, Portugal, Spain, South Africa, Sweden, Switzerland, and the Netherlands. The mean maximum head movement (in one direction) was 86 degrees for the youngest drivers, 72 degrees for drivers ages 40 to 59, 67 degrees for drivers ages 60 to 69, and 59 degrees for drivers age 70+. With regard to the crash reduction effectiveness of rumble strips placed on intersection approaches, Harwood (1993) reported that rumble strips can provide a reduction of at least 50 percent in the types of crashes most susceptible to correction, including crashes involving running through a STOP sign. Avoid entries and exits with two or more lanes, except for capacity requirements. Drivers ages 6677 and older participating in focus group discussions conducted by Benekohal, et al. Subjects were instructed to use the computer keyboard to select which of four options was appropriate if the person wanted to turn left and saw the traffic signals presented. Harwood (1993) reported that several highway agencies commented that it was important to avoid the temptation to use rumble strips where they are not needed; if every intersection had rumble strips on its approach, rumble strips would soon lose their ability to focus the attention of the motorist on an unexpected hazard. Uncontrolled - none of the approaches to the intersection are controlled by a regulatory sign or traffic signal; typically found on very low-volume roads in rural or residential areas. Traditionally, field of view has not been considered as a parameter that needs to be optimized in lighting system design for intersection applications. At the point of entry, depending upon the deflection angle of the splitter island, there are critical seconds where confirmation that no conflict exists with a vehicle already in the roundabout requires a glance orientation that well exceeds 90. The most frequent factor was "fast moving traffic on my rear bumper," by 24 percent of the respondents, followed by "road sign name that is too small to read" by just over 20 percent of the participants. A driver comprehension analysis conducted in a laboratory setting with drivers 3060 years of age and older showed that green displays (those with the circular green indication alone, green arrow alone, or combinations of circular green and green arrow on the left-turn signal) were correctly interpreted with widely varying frequency, depending on the signals shown for the turning and through movements (Curtis, Opiela, and Guell, 1988). Exclusive timing is a countermeasure where traffic signals are used to stop motor vehicle traffic in all directions simultaneously for a phase each cycle, while pedestrians are allowed to cross the street. Results showed that the aging drivers did not have longer PRT than younger drivers, and in fact the 85th percentile PRT closely matched the AASHTO design equation value of 2.0 s. The 90th percentile PRT was 2.3 s, with outlying values of 3 to 4 s. The median daytime PRT was approximately 1.3 s. Interestingly, it was found that typical driver actions did not follow the stop/search/decide maneuver sequence implied by the model; in fact, drivers continued to search and appeared ready to terminate or modify their maneuver even after they had begun to move into the intersection. YIELD SIGNS. Older pedestrians had a slower walking speed with the 15th percentile being 3.03 ft/s (0.9 m/s). While the option for dimming on a location-by-location basis should not be excluded, from the standpoint of aging driver needs, there is no compelling reason to recommend widespread reduction of traffic signal intensity during nighttime operations. There was also a significant reduction in the percentage of pedestrians who were running or had an aborted crossing after the countdown signal installation. It is generally agreed that the visibility issues associated with circular signals relate to the following factors: minimum daytime intensity, intensity distribution, size, nighttime intensity, color of signals, backplates, depreciation (light loss due to lamp wear and dirt on lenses), and phantom (apparent illumination of a signal in a facing sun). Later research (Agent, 1988) recommended the following operational improvements at intersections controlled by STOP signs: (1) installing additional advance warning signs; (2) modifying warning signs to provide additional notice; (3) adding stop lines to inform motorists of the proper location to stop, to obtain the maximum available sight distance; (4) installing rumble strips, transverse stripes, or post delineators on the stop approach to warn drivers that they would be required to stop; and (5) installing beacons. In the six years prior to the roundabout, there were 45 reported intersection crashes with an average of eight crashes per year. (1997) investigated the effects of a 3-s LPI on pedestrian behavior and conflicts with turning vehicles at three urban intersections in St. Petersburg, FL. For the YIELD sign, the recommended minimum maintained levels ranged between 24 and 39 cd/lux/ m2. The peak hour total approach volume is 1,000 vehicles (Jacquemart, 1998). Early roundabout operations gave priority to drivers entering the circle ("nearside priority"), which caused circulating traffic to come to a complete stop resulting in grid-lock. In this same study, it was found that the likelihood of a driver making an RTOR maneuver is reduced by intersection skew angles that make it more difficult for the driver to view conflicting traffic. (1982). Protected/permissive phasing resulted in the most severe crashes for all age groups (as determined by a severity index) of the three phasing options. At the wider intersection, mean crossing speeds were 4.9 ft/s for pedestrians ages 20-59; 4.27 ft/s for pedestrians ages 60-65, and 3.6 ft/s for pedestrians age 66 and older. Maybe you're thinking about a CD vs. high-yield savings account, or maybe, you're toying with the idea of CDs vs. money market accounts. Tapered offset left-turn lanes generally require raised medians of 24 ft or more in width. Agent concluded that at rural sites, transverse pavement striping should be applied approximately 1,200 ft in advance of the STOP sign to significantly reduce approach speeds. Example of continental crosswalk markings, Figure 88. Motorcycle riders. Description of Practice:Pavement messages in advance of an intersection may be used to supplement critical warning sign messages, such as the stop ahead and yield ahead signs. pedestrians who start on the WALK signal walk slower than those who cross on either the flashing DONT WALK or steady DONT WALK; the slowest walking speeds were found on local streets while the faster walking speeds were found on collector-distributors; sites with symbolic pedestrian signals had slower speeds than sites with word messages; pedestrians walk faster where RTOR is not permitted, where there is a median, and where there are curb cuts; faster crossing speeds were found at sites with moderate traffic volumes than at sites with low or high vehicle volumes. Stamatiadis, Taylor, and McKelvey (1991) found that at stop-controlled urban intersections, the percentage of drivers age 75 and older involved in right-angle crashes was more than double that of urban signalized intersections. For design purposes, the authors concluded that a mean value of 2.5 s and an 85th percentile value of 3.75 s would be appropriate. However, for the higher-speed approach (55 mph), the minimum gaps accepted by the older drivers (females = 7.11 s; males = 6.23 s) were not significantly larger than the younger drivers (females = 6.0 s; males = 5.26 s). Additionally, all intersections were controlled by traffic-responsive semi-actuated signals, and all left-turn maneuvers were completed during the permissive left-turn phase at all study sites. Roberts and Roberts (1993) reported that common arthritic illnesses such as osteoarthritis, which affects more than 50 percent of the elderly population, and rheumatoid arthritis, affecting 1 to 2 percent, are relevant to the tasks of turning and gripping the steering wheel. When there were two lanes of opposing traffic, lagging protected/permissive tended to have the worst crash rate. At unsignalized intersections, the highest percentage of fatalities resulted from right-angle collisions (25 percent). With regard to intersection design issues on two-lane rural highways, TEH (1999) states that: "Skew angles in excess of 75 degrees often create special problems at stop-controlled rural intersections. Figure 73. Meanwhile, drivers over the age of 65 had a higher correct response rate with flashing circular red indication and flashing yellow permissive indications than all other age groups. As noted earlier, studies performed to date to evaluate the safety performance of roundabouts have not included driver age as a variable. Signal light colors were identified more incorrectly for night conditions than for day conditions. With the exception of speed during the turn, kinematic measures showed significantly better performance associated with the improved intersection, and there were significantly fewer behavioral errors with the improved design. They conducted three separate on-road studies to measure driver perception-brake response time to several stopping sight distance situations. A 7-point Likert scale was used for the ratings, with the endpoints being significantly lower or higher (e.g., 1 = the alternative drive was significantly lower than the baseline, 7= the alternative drive was significantly higher than the baseline) and the midpoint of the scale (4) meaning no change. For the existing midblock locations, a general observation is that the continental marking was detected at about twice the distance upstream as the transverse marking during daytime conditions. ST-052 (TEH, 2005); andVehicle Traffic Control Signal Heads: Light Emitting Diode Vehicle Arrow Traffic Signal Supplement, TEH Standard No. Description of Practice:Within the last five years, interest in a set of intersection designs collectively called "innovative" or "alternative" has grown rapidly. Other timing strategies include early release timing, late release timing, and exclusive timing. The authors cited regression-to-the-mean as a factor in this crash reduction, but noted that the decline in pedestrian injury crashes was consistently greater with the countdown sites than the non-countdown sites. The induced exposure method was used to determine crash rate for drivers in three different age groups: 14-24 years old, 25-64 years old, and 65 years and older. Consistent findings were reported in Hagenauer, et al. With respect to the PRT values, recommendations include increasing the 2.0-s and 2.5-s values used in Case I and Case II calculations, respectively, to 3.4 s. It was also recommended that the PRT value for Case III scenarios be redefined. The decision to install a traffic signal is based on an investigation of physical and traffic flow conditions and data, including traffic volume, approach travel speeds, physical condition diagrams, crash history, and gap and delay information (Wilshire, 1992). (2007) recommended that the supplemental panel bearing the legend "TO TRAFFIC IN CIRCLE" be placed immediately below the R1-2 Yield signs on both sides of the road at the entrance to a roundabout, as shown inFigure 85. Figure 76. Countermeasure 1 (inverted isosceles triangle pavement markings) did not improve participants' understanding of the yield treatment at the entrance of the roundabout; and some participants thought they were traveling in the wrong direction, given that the triangles were pointed toward the drivers entering. Figure 80. Hallmark and Mueller (2004) indicated that left-turn volumes were not included in this study (hence the decision to use induced exposure); that may be one of the reasons why protected/permissive phasing performed worse compared to permissive phasing. Neuman (1989) also argued that a PRT of 2.5 s for SSD may not be sufficient in all situations, and can vary from 1.5 s to 5.0 s depending on the physical state of the driver (alert versus fatigued), the complexity of the driving task, and the location and functional class of the highway. V = operating speed on the major road (mph). One set of intersections included roadways that met at a 90-degree angle (improved) and roadways that met at an angle less than 75 degrees (unimproved). For the 132 signalized intersections in 6 local jurisdictions in Arizona, samples ranged from 4 months to 4 years, all between 1981 and 1989. In the practice of coming to a stop, followed by a look to the left, then to the right, and then back to the left again, the aging driver's slowed scanning behavior allows approaching vehicles to have closed the gap by the time a crossing maneuver finally is initiated. This highlights problems aging drivers may have determining acceptable gaps and maneuvering through traffic streams when there is no protective phase. Traffic control signals are used at intersections where traffic volume is high. Always slow down and proceed without stopping. Knoblauch, et al. (1982) study cited earlier, Hauer (1988) stated that because channelization in general serves to simplify an otherwise ambiguous and complex situation, the channelization of an existing intersection might enhance both the safety and mobility of aging persons, as well as enhance the safety of other pedestrians and drivers. (1997) conducted a field study evaluating four right-turn lane geometries to examine the effect of channelized right-turn lanes and the presence of skew on right-turn maneuvers made by drivers of different ages. In this same vein, it was reported inTransportation Research Circular 382(Transportation Research Board, 1991) that the aging driver, having poorer vision, slower physical reaction time, lower degree of awareness, and reduced ability to maneuver the vehicle, is more likely to be negatively affected by a raised median than is the average driver; and, because medians are fixed objects, when they are struck they pose a serious threat of loss of control, especially for aging drivers. For example, Phoenix, Arizona, a city with a large aging driver population, has been using "jumbo" street name signs at signalized intersections since 1973. FARS data showed that approximately 84 fatal crashes per year occurred involving a right-turning vehicle at an intersection where RTOR is permitted; however, because the status of the traffic signal indication is not available in this database, the actual number of fatal crashes that occurred when the signal was red is not known. Approximately 10 percent of men and women between ages 65 and 75 have (best corrected) acuity worse than 20/30, compared with roughly 30 percent over the age of 75 (Kahn, et al., 1977). Janoff (1990) noted that the evidence to support these ratios is somewhat variable, and support of these recommendations is mixed. Each sign contained three place names, each containing six letters (from the same font). Anticipated Benefits to Aging Road Users:Increasing the conspicuity of traffic control devices at intersections and reducing any ambiguity about the information they convey may be expected to have the greatest benefits for those with (age-related) visual and cognitive deficits. Crashes were reduced by approximately 24 percent, and injury and fatal crashes were reduced by approximately 16 percent. Although Agent emphasized that beacons do not eliminate the problem of drivers who disregard the STOP sign, flashing beacons used in conjunction with STOP signs at isolated intersections or intersections with restricted sight distance have been consistently shown to be effective in decreasing crashes by increasing driver awareness and decreasing approach speeds (California Department of Public Works, 1967; Cribbins and Walton, 1970; Goldblatt, 1977; King, et al., 1978; Lyles, 1980). This model uses MRVD (Minimum Required Visibility Distance), which is the shortest distance at which a sign must be visible to enable a driver to respond safely and appropriately, and includes the distance required for a driver to detect the sign, recognize the message, decide on a proper action, and make the appropriate maneuver before the sign moves out of the driver's view.

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