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. Jacquemart (1998) examined the before and after crash data of 11 roundabouts in the U.S. TheMUTCDhas adopted similar wording, which is shown as part of Recommendation C of Design Element 16. Researchers studying wrong-way movements at intersectionsparticularly the intersection of freeway exits with secondary roadshave found that such movements resulted from left-turning vehicles making an early left turn rather than turning around the nose of the median, and have proposed and tested several countermeasures. Taking speed and sign application into account, the recommended (minimum maintained, below which the sign should be replaced) retroreflectivity for STOP signs resulting from this research ranged between 10 cd/lux/ m2up to 24 cd/lux/ m2for the sign background (red) area, with significantly higher values for the sign legend. In the following calulators L is the length of vertical curve in feet, S is the sight distance in feet. They noted that while it is desirable to provide a reasonable margin of safety to accommodate incorrect or delayed driver decisions, there are substantial costs associated with providing sight distances at intersections; therefore, it is important to understand the derivation of ISD requirements and why it is reasonable to expect a safety benefit from tailoring this design parameter to the needs of aging drivers. However, in designing a new intersection, he stated that the presence of islands is unlikely to offset the disadvantage of large intersection size for the pedestrian. Modern roundabouts are an intersection design that has been in use in Europe and Australia for decades, but have more recently come into their own in the United States. For older drivers, these times were 0.51 and 0.53 s, for 20 mph and 30 mph, respectively. The left-turn lane offsets required to achieve the minimum required sight distances calculated using this model are shown inFigure 77, in addition to the offsets required to provide unrestricted sight distance. One of the improved intersections included left-turn lanes offset at 4 to 5 feet to improve the sight distance of oncoming vehicles by the left-turning driver. A The specification of standard values for peak intensity is important because the distribution of light intensity falls off with increasing horizontal and vertical eccentricity in the viewing angle. They should also benefit from carrying out this search without dividing their attention to potential conflicts with pedestrians crossing to the corner island. Observations were made during 3,242 crossings during a baseline period (4.0 ft/s design crossing speed) and 2 and 6 weeks after the flashing DONT WALK interval was extended to allow for the slower crossing speed under study. Still images were photographed of a roundabout unfamiliar to all participants (in Washington State), every 10 ft during an approach to and going around the roundabout, for a total of 64 images. The use of an advance street name plaque (W16-8) with an advance warning crossroad, side road, or T-intersection sign (W2-1, W2-2, W2-3, and W2-4) provides the benefit of additional decision and maneuver time prior to reaching the intersection. Even greater consensus was shown in this study regarding sign location for lane assignment. Where an acceleration lane was available, 65 percent of young/middle-aged drivers continued through without a complete stop, compared with 55 percent of drivers age 6574 and 11 percent of drivers 75 and older. Street name signs should therefore be readable at 300 ft at speeds of 35 mph, and at 450 ft at 55 mph. Only one of the 38 roundabouts has painted (marked) splitter islands. These aging drivers stated that they would prefer to have rumble strips in the pavement to warn them of upcoming concrete medians and to warn them about getting too close to the shoulder. Figure 79. While the Montpelier, VT, Keck Circle Roundabout was under construction, the Roundabout Demonstration Committee prepared educational materials that included a brochure providing safety rules for drivers and pedestrians, as well as news releases and public service announcements in response to negative public reaction during construction, and negative commentary from local morning radio personalities (Redington, 1997). understand the severity of a sight distance restriction, how the restriction However, a relative insensitivity to approach (conflict) vehicle speed was shown for older versus younger drivers, in that younger drivers adjusted their gap judgment of the "last safe moment" to proceed with a turn appropriately to take higher approach speeds into account, while older drivers as a group failed to allow a larger gap for a vehicle approaching at 60 mph than for one approaching at 30 mph. In Case II, SSD is the design value; thus, the PRT is 2.5 s. For all Case III scenarios and Cases IV and V, the PRT is assumed to be 2.0 s. Refer toTable 14to cross-reference the 1994 vs. 2011 intersection scenarios. Knoblauch, et al. Observed changes in pedestrian-vehicle conflicts at the smaller intersection were contaminated by an increase in the proportion of pedestrians (in the young and young/middle age groups only) who crossed illegally (i.e., began to cross during the flashing DONT WALK phase); consequently, sustained differences between the baseline and experimental phases were not demonstrated. This compared with 22 percent or less for the younger age groups. Paragraph 3 of Section 4E.13 states that if additional crossing time is provided by means of an extended pushbutton press, a PUSH BUTTON FOR 2 SECONDS FOR EXTRA CROSSING TIME (R10-32P) plaque (seeFigure 91) shall be mounted adjacent to or integral with the pedestrian pushbutton. In a study of 83 roundabouts in France (Centre D'Etudes Techniques de L'Equipment de l'Ouest, 1986) in Jacquemart (1998), it is also concluded that roundabouts with smaller diameters have fewer crashes than larger roundabouts or those with oval circles (seeTable 36). However, there is some inconsistency among reference sources concerning the degree of skew that can be safely designed into an intersection. There are treatments currently within the Handbook that discuss features at roundabout intersections that can benefit aging drivers; however, roundabouts themselves can be a beneficial treatment over a traditional stop- or signal-controlled intersection if properly designed to meet the needs of that location. When cited, the old-old group was more likely to have disregarded the STOP sign than the other two driver groups. To accurately describe this research, it is necessary to use a trademarked name; however, this does not imply an endorsement of this product by the U.S. Government. 160 Exhibit 6-31. ST-052 (TEH, 2005); andVehicle Traffic Control Signal Heads: Light Emitting Diode Vehicle Arrow Traffic Signal Supplement, TEH Standard No. (1996) provided a list of conditions that may lead a driver to misinterpret an intersection to be all-way stop controlled, which would justify a supplemental sign treatment. AASHTO values (for both uncontrolled and stop-controlled intersections) for available sight distance are measured from the driver's eye height (currently 3.5 ft above the roadway surface) to the object to be seen (currently 3.5 ft above the surface of the intersecting road). Malfetti and Winter (1987), reporting on the unsafe driving performance of drivers age 55 and older, noted that aging drivers frequently failed to respond properly or respond at all to road signs and signals; descriptions of their behavior included running red lights or STOP signs and rolling through STOP signs. Thus, they concluded that the older drivers were not necessarily reacting inappropriately to the signal. For the remaining crossings, they determined that the walking speed values for older pedestrians were lower than those for younger people. Drivers in two subject groups, ages 3050 and 6080, depressed a brake pedal to watch a video presentation (on three screens), then released the pedal when it was judged safe to make a left turn; half of each age group had a restricted range of neck movement as determined by goniometric measures of maximum (static) head-turn angle. However, passive detection also can be used to detect pedestrians within the crosswalk that may need more time to complete their crossing maneuver. A Policy on Geometric Design of Highways and Streets Garber and Srinivasan (1991) conducted a study of 2,550 crashes involving pedestrians that occurred in the rural and urban areas of Virginia to identify intersection geometric characteristics and intersection traffic control devices that were predominant in crashes involving aging pedestrians. The rationale for mixed-case letters is reported above; the case for enhancements of street name letter fonts follows. to implement mitigation strategies. The final measure of interest was the mean distance traveled by the lead pedestrian during the LPI condition, which averaged 8.5 ft. Section 3B.18 of the 2009 MUTCD contains basic information about crosswalk markings; however, some States adopt their own supplement or manual on traffic control devices and some develop policies and practices for subjects not discussed in the MUTCD, so differences in markings occur among States, cities, and other jurisdictions. In addition, the specific geometric characteristics, traffic control devices (including signs, signals, and markings), and pedestrian signals that seem to contribute to aging pedestrians' difficulties at intersections are discussed. Further, crash percentages increased significantly for aging drivers when an intersection contained flashing controls, as opposed to conventional (red, yellow, green) operations. ISD for two-way flashing operations should be determined by Case B guidance. that provides at least the minimum stopping sight distance through the (1995) conducted a series of field studies to quantify the walking speed, start-up time, and stride length of pedestrians younger than age 65 and pedestrians 65 and older under varying environmental conditions. Both Florida and Maryland used SIDRA software (Australian methodology) in those guidelines to conduct an analysis of the capacity of a planned roundabout, which is available through McTrans at the University of Florida at Gainesville. 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. Hulbert, Beers, and Fowler (1979) found a significant difference in the percentage of drivers younger than age 49 versus those older than age 49 who chose the correct meaning of the red arrow display. The drivers were asked to respond to the following question by selecting either GO, YIELD-wait for gap, STOP-then wait for gap, or STOP: "If you want to turn left, and you see the traffic signals shown, you would.". For protected/permissive operation, the circular green alone was correctly answered by only 50 percent of the respondents, while the green arrow in combination with the circular green had approximately 70 percent correct responses. Garvey, Pietrucha, and Meeker (1997) state that guide signs are read using both legibility and recognition criteria, depending on the familiarity of a traveler with the location words used on the signs. An initial pilot evaluation was performed at nine sites, which found that pedestrian injury crashes dropped from 27 to 13 after countdown signal installation, a 52% reduction, with a slight decline in pedestrian crashes for the primary untreated comparison group. Next, all roundabouts were reported to have the standard YIELD sign, although often it was supplemented by an additional plate with specific instructions, such as "TO TRAFFIC ON LEFT;" "TO TRAFFIC IN ROUNDABOUT;" or "TO TRAFFIC IN CIRCLE;" or with the international roundabout symbol, which is three arrows in a circular pattern. It is the minimum distance require within which a vehicle moving at design speed can be stopped without colliding with a stationary object. The Clearview fonts will be referred to as Clear Condensed 100, Clear Condensed 112, Clear 100, and Clear 112 throughout the remainder of this section. The backplate, rather than the sky, becomes the background of the signals, enhancing the contrast. The fact that aging drivers (and females) were less likely to position themselves (i.e., pull into the intersection) in the field studies highlights the importance of providing adequate sight distance for unpositioned drivers, for all left-turn designs. The table below gives a few values for the decision sight distance (AASHTO, 1994). Case B: Intersections with Stop Control on the Minor Road. The sample contained 88 drivers age 65 and older. However, quick inspection of the crash frequencies provided by site indicate that only the roundabout retrofitted from a signalized intersection showed an increase in crashes in the after period; the other five sites (1-way and 2-way stop controlled) showed decreases in crash frequency in the after period (in the range of 60 to 70 percent). One of the advantages of using curbed medians and intersection channelization is that it provides a better indication to motorists of the proper use of travel lanes at intersections. This understanding of the downstream intersection geometry is accomplished by the driver's visual search and successful detection, recognition, and comprehension of pavement markings (including stripes, symbols, and word markings); regulatory and/or advisory signs mounted overhead, in the median, and/or on the shoulder in advance of the intersection; and other geometric feature cues such as curb and pavement edge lines, pavement width transitions, and surface texture differences connoting shoulder or median areas. For example, a corner radius of less than 5 ft is not appropriate even for P design vehicles (passenger cars), whereas a corner radius of 2030 ft will accommodate a low-speed turn for P vehicles, and a crawl-speed turn for SU vehicles (single unit truck, 30 ft in length) with minor lane encroachment. However, Lerner et al. Five design elements were evaluated: (1) advance warning signs; (2) lane control signs; (3) directional signs; (4) yield treatments; and (5) exit sign treatments. Aside from (conflict vehicle) motion detection, an additional concern is whether there are age differences in how well drivers understand the rules under which the turns will be madethat is, whether aging drivers have disproportionately greater difficulty in understanding the message that is being conveyed by the signal and any ancillary (regulatory) signs. In this study, 100 subjects divided across three age groups were observed as they drove their own vehicles around test routes using the local street network in Arlington, Virginia. This puts them at a higher crash risk, because at the same time they are causing a shorter separation from the following vehicle, they are steering slower and accelerating slower than the younger drivers, and causing more effects on major road traffic. In the Zegeer et al. 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. The mean walking speed for females age 66 and older was 3.28 ft/s. Stopping sight distance is measured from the driver's eyes, which is 3.5 feet above the pavement surface, to an object 2 feet high on the road. In other focus group discussions conducted to identify intersection geometric design features that pose difficulty for aging drivers and pedestrians (Staplin, et al., 1997), drivers mentioned that they have problems seeing concrete barriers in the rain and at night, and characterized barriers as "an obstruction waiting to be hit.". When the two left-turn lanes are exactly aligned, the offset distance has a value of zero. compared with a similar location with no such features. The means for aging drivers are generally between 40 ft/in and 50 ft/in; however, the 85th percentile values reported are between 30 ft/in and 40 ft/in (Sivak, Olson, and Pastalan, 1981; Kuemmel, 1992; Mace, Garvey, and Heckard, 1994). A total of 134 participants were tested in three age groups: 18 to 29, 30 to 59, and 60 and above. At unsignalized intersections, aging drivers showed the highest crash frequency on major streets with two lanes in both directions (a condition most frequently associated with high-speed, low-volume rural roads), followed by roads with four lanes, and those with five lanes in both directions. Regarding channelization for mid-block left-turn treatments, Bonneson and McCoy (1997) evaluated the safety and operational effects of three mid-block left-turn treatments: raised curb medians; two-way, left turn-lanes; and undivided cross sections. Analysis of the walking speeds of 3,458 pedestrians younger than age 65 and 3,665 pedestrians age 65 and older crossing at intersections showed that the mean walking speed for younger pedestrians was 4.95 ft/s and 4.11 ft/s for older pedestrians. Such a condition may not necessarily meet traffic signal warrants. Researchers have postulated further safety gains by adding a 1-inch to 3-inch yellow retroreflective strip around the perimeter to "frame" the backplate. Also noted were difficulties reading traffic signs with too much information in too small an area, and/or with too small a typeface, which results in the need to slow down or stop to read and respond to the sign's message. Since aging drivers less frequently positioned themselves in the field study, the design value for this factor (maneuver time) should be based on that obtained for unpositioned drivers. Additionally, selection of a design vehicle is generally based on the largest standard or typical vehicle type that would regularly use the intersection. (1991) showed that older adults tend to overestimate approaching vehicle velocities at lower speeds and underestimate at higher speeds, relative to younger adults. Thus, for a sidewalk whose centerline is 6 ft from the roadway edge, a 15-ft corner radius increases the crossing distance by only 3 ft. He recommends moving the crosswalk back one car length from the yield line for each lane of entry (i.e., one car length for a one-lane entry, two car lengths for a two-lane entry, or three car lengths for a three-lane entry). A great deal of existing research on roundabouts has not been conducted specifically from the perspective of the aging road user, but the benefits apply to drivers and pedestrians of any age. The profile shows the amount of stopping sight distance at each location The time duration for each response was also recorded. Drivers approaching an unsignalized intersection must be able to detect the presence of the intersection and then detect, recognize, and respond to the intersection traffic control devices present at the intersection. Drivers ages 6677 and older participating in focus group discussions conducted by Benekohal, et al. In addition, there is no discussion of driver age in the study results. of the hill. This countermeasure resulted in an overall reduction in RTOR violations and pedestrian conflicts. A survey was administered in 15 senior centers in counties with high-speed roads within their boundaries. In the second photo, the back of the car is seen descending the far side Thus, the conspicuity of such elements as curbs, medians, and obstacles, as well as all raised channelization, is of paramount importance in the task of safely approaching and choosing the correct lane for negotiating an intersection, as well as avoiding collisions with the raised surfaces. Results indicated that color-vision-deficient drivers had significantly longer reaction times than drivers with normal color vision, and aging drivers had longer reaction times compared to younger drivers. Interviews and assessments were conducted with 1,249 persons age 72 and older from the New Haven, CT community of Established Populations for Epidemiologic Studies of the Elderly, to determine walking speeds and self-reported difficulty with crossing the street as pedestrians (Langlois, et al., 1997).