what do you do in an intersection?

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). Drivers referred to TWLTL's as 'suicide lanes." The spatial visual functions of acuity and contrast sensitivity are important in the ability to detect/recognize downstream geometric features such as pavement width transitions, channelized turning lanes, island and median features across the intersection, and any non-reflectorized raised elements at intersections. (2000) evaluated the change in crashes following conversion of 24 intersections in urban, suburban, and rural environments in 8 States (California, Colorado, Florida, Kansas, Maine, Maryland, South Carolina, and Vermont) from stop-sign or signal control to modern roundabouts. A study of pedestrian crashes conducted at 31 high-pedestrian crash sections in Maryland between 1974 and 1976 showed that pedestrians age 60 and older were involved in 53 (9.6 percent) of the crashes, and children younger than age 12 showed the same proportions. Diagram of Restricted Crossing U-Turn Intersection (Image Credit: Debbie Murillo, Texas A&M Transportation Institute). In establishing minimum daytime intensity levels for (circular) traffic signals, the two driver characteristics that are considered with regard to the need to adjust peak intensity requirements are color anomalies and driver age. All Rights Reserved. This suggests that at stop-controlled intersections, older drivers in particular, older female driversare more likely to collide with speeding vehicles approaching on the major road. Roundabout Advance Warning Sign Recommended by Lord et al. As a group, however, these visual functions do not appear to have strong implications for highway lighting practice, with the possible exception of the "useful field of view." The number of foreign and domestic highway organizations that specify a minimum standard for peak daytime traffic signal intensity is larger than the number of research studies upon which those standards are based. For the word legibility study, subjects were presented with only one word on a sign, and were required to read the word. A detailed discussion of the outputs from the model exercise is provided in the publication Intersection Geometric Design and Operational Guidelines for Older Drivers and Pedestrians (Staplin, et al. (2007) compared older and younger driver performance at improved and unimproved intersections in a high-fidelity, virtual reality driving simulator to test the effectiveness of FHWA's recommendations for intersection designs to accommodate older road users. TheMUTCD(section 3B.10, Approach Markings for Obstructions) specifies that pavement markings shall be used to guide traffic away from fixed objects (such as median islands and raised channelization islands) within a paved roadway. Alignment of Left-Turn Lanes for Negative and Positive Offset. ST-011B (TEH, 1985a);Traffic Signal Lamps, TEH Standard No. 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. A study by McFarland, et al. The simulation results did not point to what steps would be effective. Example of bar pairs crosswalk markings. They offered that the circular red symbol on the sign helps draw drivers' attention to it, particularly as intersections are associated with a preponderance of signs and information, and recommended that it should be added to theMUTCDas an alternate or approved as a replacement to the current R10-11a design. At an intersection where there is no stop sign or traffic signal (with the exception of roundabouts), drivers must yield to vehicles coming from the right. Uncontrolled intersections are typically found in residential areas or rural areas. Type I engineering grade sheeting was used for all signs. The yellow arrow display was more often treated as a last chance to complete a turn when compared with a circular yellow indication. (1993) stated that the rationale for gap acceptance as an ISD criterion is that drivers safely accept gaps much shorter than 15.2 s routinely, even on higher speed roadways. Swinging too wide to lengthen the turning radius and minimize rotation of the steering wheel ("buttonhook turn") while turning left or right is a common practice of drivers who lack strength (including aging drivers) or are physically limited (McKnight and Stewart, 1990). At suburban intersections, it is therefore suggested that the median should not generally be wider than necessary to accommodate pedestrians and the appropriate median left-turn treatment needed to serve current and anticipated future traffic volumes. A survey was administered in 15 senior centers in counties with high-speed roads within their boundaries. Description of Practice:Another APS treatment is passive detection. The leading violation types for all aging drivers in descending order were failure to yield right-of-way, following too closely, improper lane usage, and improper turning. There are apparent tradeoffs here, however; the leading sequence was associated with a higher conflict rate with pedestrians and a higher rate of run-the-red conflicts (drivers turning left during the clearance interval for opposing traffic), while the intersections with a lagging sequence were associated with a significantly higher rate of indecision conflicts than the leading intersections due to violations in driver expectancy. The 15th percentile speed for the young compliers was and was 3.08 ft/s for the older compliers. (1990) found that older drivers (ages 6580) demonstrated a need for larger letter sizes to discern a message on a guide sign, compared with a group of younger drivers (ages 1949). Description of Practice:A broad range of technologies can be classified as Accessible Pedestrian Signal (APS) treatments (Harkey, et al. Research findings indicated that an increase in sight distance through positively offsetting left-turn lanes can be beneficial to left-turning drivers, particularly aging drivers. Staplin, et al. The problems are somewhat moderated when right turns are initiated from a stop, because the turn can be made more slowly, which reduces difficulties with short radii. Aging drivers' decreased contrast sensitivity, reduced useful field of view, increased visual search and decision timesparticularly in response to unexpected eventsand slower vehicle control during movement execution combine to put these highway users at greater crash risk when approaching and negotiating intersections. Analysis of the free-flow speeds showed that all factors (age, gender, and geometry), and their interactions, were significant. There was no significant interaction between font and material, however. Most dangerous intersections in Phoenix are all on the west side A comparison between 1994 AASHTO values and the 95th percentile clearance times demonstrated by positioned drivers and unpositioned drivers in this study is presented inTable 15. The lower percentage of nighttime crashes of aging drivers may be due to a number of factors, including reduced exposureaging drivers as a group drive less at nightand a self-regulation process whereby those who do drive at night are the most fit and capable to perform all functional requirements of the driving task (National Highway Traffic Safety Administration, 1987). Burnham (1992) noted that signs located over the highway are more likely to be seen before those located on either side of the highway. This conclusion was based on experiments in which the background luminance was 5,142 cd/m2. Thus, 36 percent are at least 2 lanes wide. A two-way stop requires a driver to cross traffic streams from either direction; this poses a potential risk, because cross traffic may be proceeding rapidly and drivers may be less prepared to accommodate to errors made by crossing or turning drivers. This finding underscores the need for larger lettering on street name signs, the use of overhead street name signs, and advance placement of street name signs. Recognize the kind of intersection. The young-old drivers as well as the old-old drivers more frequently failed to yield than the middle-aged drivers. One hundred subjects divided across three age groups drove their own vehicles around test routes using the local street network in Arlington, VA. A treatment for an all-red clearance interval logically follows, with length determined according to the TEH (1992). Five design elements were evaluated: (1) advance warning signs; (2) lane control signs; (3) directional signs; (4) yield treatments; and (5) exit sign treatments. (2007). At the same time, concerns have been raised about confusion by aging motorists regarding the meaning of arrow signal indications elsewhere in thisHandbook. Lord, et al. Of course, a conflict must be seen before any cognitive processing of this sort proceeds. The next-best performing signal design was the Modified Backplate. The two through lanes were the only ones that had a direct effect on the right-turn maneuver. A recent NCHRP report shows that intersection lighting can reduce total nighttime crashes by 21 percent and nighttime injury crashes by 27 percent. Intersection Safety | FHWA - Federal Highway Administration In these tables, it is recommended that the existing treatment remain in place when the benefit-cost ratio (in terms of delay and safety) is less than 1.0, and when the benefit-cost ratio exceeds 2.0, it is recommended that the engineer consider adding the alternative treatment. 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. An empirical Bayes analysis, which included a comparison group to control for trend effects and a reference group to adjust for regression to the mean, indicated a nearly 15% drop in the number of crash claims following introduction of the enhanced-conspicuity backplates. One of the common characteristics of these alternative designs is that they typically accommodate left-turns in unique ways, with the end result that left-turns at the intersection are greatly reduced, if not eliminated. A new set of 24 subjects was recruited for the legibility study, with half completing the study during daytime (mean age = 71.3 years) and half at nighttime (mean age = 73.9 years). Detection and avoidance of such hazards requires visual and response capabilities known to decline significantly with advancing age. 5-6, Pgs. The authors noted that the walking speed of aging pedestrians varies according to functional classification, gender, and intersection type, and stated that approximately 95 percent of pedestrians in this study would be accommodated using a design walking speed of 2.62 ft/s. Measures of effectiveness included percent of correct responses to the study scenarios and response time. That is, separate maneuver-time measures were obtained, depending on whether the drivers positioned themselves within the intersection prior to turning. Knoblauch, et al. On approaches with channelized right-turn lanes, drivers age 2574 were much less likely to stop before making a RTOR. 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. The most common solution to this problem is to offset the left-turn lanes, using either parallel offset or tapered offset left-turn lanes. Case B: Intersections with Stop Control on the Minor Road. 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. These general rules were created to decrease the chance of a collision and to alert other drivers when right of way should be given. They proposed an enlargement from 30 x 30 in to 36 x 36 in at well-traveled intersections or at intersections of small country lanes with State highways. FHWA released two Roundabout Guides (Robinson, et al. Stop-controlled intersections have one or more "STOP" signs. However, this result was for recognition of words that drivers already knew would appear on the signs. Aging persons' sensitivity to visual contrast (the ability to see objects of various shapes and sizes under varying levels of contrast) also declines beginning around age 40, then declines steadily as age increases (Owsley, Sekuler, and Siemsen, 1983). Average walking speeds for pedestrians using a cane or crutch were 2.62 ft/s; for pedestrians using a walker, 2.07 ft/s; for pedestrians with hip arthritis, 2.24 to 3.66 ft/s; and for pedestrians with rheumatoid arthritis of the knee, 2.46 ft/s. A non-channelized 90-degree intersection where drivers had the chance to make a right turn on red (RTOR) around a 40-ft radius. Lane widths are addressed in the Intersection Channelization Design Guide (Neuman, 1985). The section on Advance Intersection Lane Control signs (sign series R3-8, section 2B.22), states that when used, these signs should be placed at an adequate distance in advance of the intersection so that road users can select the appropriate lane (e.g., in advance of the tapers or at the beginning of the turn lane). The Clearview font was developed to have open, wider spaces within a letter, to eliminate the effects of irradiation/halation that is caused by bright, bold stroke widths that "bleed" into a character's open spaces, rendering it illegible. Only 7.3 percent of the population had measured walking speeds 3 ft/s, and less than 1 percent had walking speeds of 4.0 ft/s. Older drivers had significantly higher forward acceleration than the younger drivers, indicating a "panicked" attempt to successfully drive through the gap in oncoming traffic at the unimproved intersection. This design has the additional advantage of the crosswalk being located in an area where the driver is still looking ahead; older designs place the crosswalk in a location where the driver is already looking left for a break in the traffic. The images were manipulated with photo-editing software to reflect each of the three alternatives, described inTable 37. Highway signs with fluorescent sheeting have been found to be more conspicuous and can be detected at a further distance than signs with standard sheeting of the same color. For more highly complex visual environments, the intensity recommendation for the red signal is approximately doubled. Also, research has shown that aging persons have greater difficulty in situations where planned actions must be rapidly altered (Stelmach, Goggin, and Amrhein, 1988). The smaller the attentional demand required of a driver to maintain the correct lane position for an intended maneuver, the greater the attentional resources available for activities such as the recognition and processing of traffic control device messages and detection of conflict vehicles and pedestrians. Previously, however, Lunenfeld (1977) cited the considerable range of night background luminances that may occur in concluding that in some brightly lit urban conditions, or where there is considerable visual noise, daytime signal brightness is needed to maintain an acceptable contrast ratio. Crosswalk detectors at PUFFIN facilities are used to vary the pedestrian clearance times between defined minimum and maximum times; when there are large numbers of pedestrians or if slow-moving pedestrians are crossing, the clearance time is extended to provide ample time for them to complete their crossing. A high-speed road is defined as one with speeds up to 62 mph, distances up to 787 ft, and sky luminances up to 10,000 cd/m2. Next, theMUTCDstates that street-name signs should be placed at least on diagonally opposite corners so that they will be on the far right-hand side of the intersection for traffic on the major street. Without advance cueing, the decision rule was presented only on a sign mounted on the signal arm across the intersection as per standard practice, and thus was not legible until the driver actually reached the decision point for the turning maneuver. They had the opportunity to accelerate in their own lane on the cross street and then change lanes downstream when they perceived that it was safe to do so.
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