CHAPTER 26
Older Road Users

Older Driver Crash Risk, Crash Causation Factors, and Fitness to Drive

Older Driver Considerations for Markings, Signs, and Lighting

Older Driver Considerations for Curves and Merging Behavior

Older Driver Considerations for Work Zones—Signs

Older Driver Considerations for Work Zones—Markings and Channelization

Older Driver Considerations for Intersections—Left Turns

Older Driver Considerations for Intersections—Roundabouts

Older Driver Considerations for Intersections—Signs

Older Driver Considerations for Intersections—Pavement Markings and Signals

Note: The guidelines presented in this chapter have been drawn primarily from reference sources focused on designing roadways for the older road user, which generally refers to road users aged 65 or older. These sources include research studies that have examined older road user behaviors and performance with a range of design, operational, and traffic engineering elements. In many instances, the guidelines do not present any new information relative to what can be found in standard reference sources such as the MUTCD. However, the guidelines always highlight some design feature that is linked in some way to known limitations of older road users (e.g., vision, cognition) and (following Brewer et al., 2014), reflect the most conservative design value among present options in the existing reference sources.

Although the focus and terminology in this chapter are on the older road user, much of the content may apply to drivers with other impairments, such as those related to illness or injury.

OLDER DRIVER CRASH RISK, CRASH CAUSATION FACTORS, AND FITNESS TO DRIVE

Introduction

This guideline provides an overview of older driver crash statistics and crash characteristics and describes how changes in driversʼ functional capabilities as they age contribute to reduced capacity to meet the demands of the driving task. This guideline also discusses how well older drivers self-assess their fitness to drive and regulate their driving to reduce crash potential and risk.

In 2021, there were 55.8 million people 65 years old and older in the United States, comprising 17% of the total population (1), and this number is expected to increase to 72.1 million by 2030 (2). Importantly, older drivers made up approximately one-fifth of all licensed drivers in 2021 (1), and as people age, their ability to drive safely can decrease due to perceptual, motor, sensory, and physiological changes.

Design Guidelines

Long Description. Sensation: Older individuals may have difficulty sensing (i.e., seeing, hearing, feeling) the environment around them. This could include sensing elements such as roadway signs, pavement markings, non-reflectorized curbs and boundaries, traffic signals, pedestrians, bicyclists, and other vehicles. In addition, vision declines make it increasingly difficult to see during conditions of low lighting, glare, and when transitioning from areas of light to dark. Older individuals can also have difficulty hearing auditory cues in their environment, such as auditory signals at crosswalks. To improve the conspicuity of medians and island curbs at intersections, enhanced delineation may be used. In addition to edge lines on the road surface alongside the medians and island curbs, the vertical face of these curbs can have painted curb markings and the top surface of the curbs can be marked with retroreflectorized raised pavement markers, object markers, signs, or delineators (2, 3, 4).Attention: Attention refers to our ability to focus awareness on a particular cue or feature of the environment. Aging has a noticeable effect on attention during complex tasks. For example, older individuals can find it challenging to focus on specific information in the roadway environment, such as detecting relevant road signs, or performing multiple tasks simultaneously, such as monitoring a vehicle in front of them and checking their mirrors. To aid older drivers, it is important to consider the selection and placement of signs to reduce complexity and demand (2, 3, 4, 5, 6).Decision Making: As the speed of mental processing of information slows with aging, older individuals can be slower to make decisions about what response is appropriate for specific highway design elements and traffic conditions, and can have more difficulties multi-tasking. It is beneficial to older drivers to provide information in advance to prevent the need to make last-minute decisions. For example, in complex interchanges, providing notice early regarding lane selection for freeway exits will help prevent older drivers from having to merge across multiple lanes in a short amount of time to take the desired freeway exit (2, 3, 4).Response Execution: Older drivers may require more time to make vehicle control movements such as releasing the accelerator, pressing the brake in a controlled manner, and matching steering inputs to the roadway environment. For example, it can be more difficult for older drivers to safely adjust their steering and/or speed when approaching unexpected changes in roadway curvature and therefore cause them to drive too fast for the curve. A countermeasure to assist in the navigation of curvature may include conspicuous and redundant signage warning of upcoming changes in roadway curvature (2, 3).Physical Strength / Range of Motion: Older drivers can have difficulty turning their heads to look left and right or looking over their shoulders and may also have trouble with activities that require quick physical movements, such as abrupt turns, quickly shifting from accelerator to brake pedal, applying correct pressure for speed control, and safely maneuvering the vehicle around obstacles. For example, line of sight at right-skewed intersections can pose a challenge to older drivers if they have limited ability to physically turn their body to the left or look over their shoulder to view oncoming vehicles. Having larger vision angles at right-skewed intersections can better accommodate older drivers (2, 3, 4).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Crash Statistics for Older Drivers. From 2012 to 2021, the number of people 65 and older in the United States increased by 29% (1). There were 7,489 people aged 65 and older killed in traffic crashes in the United States in 2021, accounting for 17% of all traffic fatalities and 11% of all people injured (1). This was a 14% increase in the number of fatalities of people aged 65 and older from 2020 (1). Older drivers specifically accounted for 13% of drivers involved in fatal traffic crashes in 2021 (1).

Common Older Driver Crash Configurations and Characteristics. Studies have found that older drivers are more likely to be involved in accidents due to: weather and road surface factors; when driving on highways, at intersections and interchanges, and through curves; and when performing lane change maneuvers, merging, left turns and U-turns (1, 2, 3, 4, 7). In addition, failure to yield right-of-way and disregarding signs or signals are common crash factors in crashes with an older driver fatality (8), and older driver functional limitations lead to higher probabilities of head-on collisions (7).

Older Driver Assessment of Fitness to Drive. Some drivers may have imprecise knowledge of their age-related functional decline, but generally, they are able to self-regulate or modify their driving patterns to cope with their functional declines in specific driving skills, and performance strongly influences their adoption of compensatory driving behaviors (4, 9, 10, 11). However, some older drivers do not adjust their driving, and it has also been found that older drivers rate their fitness to drive with respect to functional ability more highly than ratings provided by their family members and are often unable to accurately judge their own driving ability (5, 10, 12). 34% of older drivers are concerned about their own driving; the most frequently mentioned driving concerns were other drivers, driving at night, visual ability and awareness, and other drivers being aggressive or reckless (13).

Design Considerations

The roadway environment coupled with individual differences (e.g., for the older road user) will often present different demands and unique performance implications based on transportation modality and as such, require different types of countermeasures to reduce crash potential for all road users (i.e., drivers, pedestrians, bicyclists, and transit users). For example, at intersections with high pedestrian volume and high turning vehicle volume, a leading pedestrian interval of three seconds or more can be helpful because it allows slower walkers to cross at least one roadway lane before conflicting turning vehicles are released (3). In a multimodal transportation network, countermeasure selection and implementation can include tradeoffs between countermeasure efficacy, safety benefits, unanticipated outcomes, and feasibility for all road users.

Cross References

Sign Design to Improve Legibility

Visibility of Lane Markings

Key References

OLDER DRIVER CONSIDERATIONS FOR MARKINGS, SIGNS, AND LIGHTING

Introduction

As people age, their ability to drive safely can decrease due to sensory changes such as vision decline. Markings, signs, and lighting are important to consider with respect to aging driver needs because older and visually impaired individuals may have difficulty seeing the environment around them, posing risks to their safety (1). Age-related vision impairment and contrast sensitivity declines can affect a driverʼs ability to read and detect signs or lane markings, especially under low-light conditions and in the presence of fog or glare (1). This guideline discusses road-based countermeasures specific to markings, signs, and lighting to support older drivers and the unique challenges they may face.

Design Guidelines

Long Description. Markings: Retroreflective values of 100 mcd / meter squared / lux or greater can help older and vision-challenged drivers adequately or more than adequately perceive pavement markings under nighttime conditions (2). Well-maintained roadway markings (e.g., painted edge lines, raised pavement markers, post-mounted markings) can reduce lane departures by providing visual cues to drivers to help them stay in their lane (3). Improve roadway delineation so older drivers and others can have better visual cues to recognize pavement markings along the roadway to enable them to maintain their lane and to safely negotiate through an intersection (3). To provide additional guidance where a through lane becomes a mandatory turn lane at an intersection or becomes a mandatory exit lane at an interchange, a “dotted” lane line can be used to separate the continuing through lane from the mandatory turn or mandatory exit lane (4). Contrast markings can be used wherever the pavement color is light to increase visibility of pavement markings (4). Highly retroreflective marking material can be used to maintain visibility under adverse driving conditions (4). Signs: Providing advance warning signs can inform older drivers of existing or potentially hazardous conditions on or adjacent to the road (3). Providing advance guide signs and street-name signs can give older drivers additional time to make necessary lane changes and route selection decisions and reduce or avoid excessive or sudden braking behavior (3). Sign legibility, use of uppercase and lowercase letters, placement, brightness, contrast, and size can help enhance older drivers' abilities to detect signs and comprehend sign messages (1, 5). Brighter sheeting materials can make signs more conspicuous, especially at locations with high levels of visual “noise,” such as guide and regulatory signs in the background (5). Fluorescent signs can help increase detection distance (5). Lighting: Lighting can be improved at intersections, horizontal curves, and railroad grade crossings to help drivers compensate for reduced visual acuity and provide additional preview distance and more time to prepare for planned actions (3).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Older adults may face a number of challenges with respect to perception and cognition. For example, information processing is generally slowed for older adults, who may have difficulties reading signs clustered together at an intersection (3). Improvements in sign placement and design can help older drivers respond more quickly and make important driving decisions (3). Furthermore, contrast sensitivity has been found to be a better predictor of the ability to read road signs than overall visual acuity, but this generally declines with age, making it potentially more difficult for older adults to detect objects in low light (e.g., nighttime) and in the presence of fog or glare (1).

According to data from the FHWA, many state departments of transportation (DOTs) report using extra-wide longitudinal pavement markings, high-contrast, black-on-white and black-on-yellow markings, and oversized glass beads to improve visibility and conspicuity of their lane lines and centerlines (5). These oversized glass beads in traditional paint markings and preformed pavement marking tape designed for rumble strip applications can help increase the retroreflectivity and thus the visibility of pavement markings at night and in wet weather conditions (4, 5). According to the Handbook for Designing Roadways for the Aging Population, preformed pavement marking tape is used statewide in Iowa, on Detroit-area freeways in Michigan, and on all interstate routes in Virginia (4). Routine use of such contrast markings such as duplicate black markings applied immediately upstream or downstream from broken line longitudinal markings (staggered markings), or black contrast markings surrounding either side of broken or continuous longitudinal markings are used in Arkansas, Colorado, Georgia, Idaho, Missouri, North Carolina, Oklahoma, Pennsylvania, Texas, Utah, Virginia, Wisconsin, and the District of Columbia (4). Any treatment that improves the contrast and consequently the detectability of lane, gore, other longitudinal pavement markings (broken or continuous), and road edge boundaries will have a larger benefit to older drivers (4). The continuous guidance information offered by treatments that enhance the contrast of pavement markings is especially helpful to aging drivers under adverse visibility conditions and when there is only a brief preview of changing roadway geometry downstream (4).

Furthermore, older drivers may be at higher risk of failing to detect advance warning signs posted at the side of the road due to loss of visual sensitivity in the periphery, a narrowing of their field of view, or a reduced ability to engage in a search of the visual periphery when, for example, environmental conditions increase demands for path guidance information (4). If an aging driver does experience any of these limitations, they should glean an extra benefit from advance warning messages presented as pavement markings if these markings are applied and maintained at contrast levels sufficient to ensure legibility (4).

Design Considerations

In-roadway crosswalk warning lights alerting drivers to the presence of pedestrians can provide safety benefits such as increasing the detection of pedestrians (6), decreasing vehicle speeds (7, 8), and increasing the proportion of drivers yielding to pedestrians (6).

Cross References

Characteristics of Lighting that Enhance Pedestrian Visibility

Sign Design to Improve Legibility

Visibility of Lane Markings

Key References

OLDER DRIVER CONSIDERATIONS FOR CURVES AND MERGING BEHAVIOR

Introduction

Curves and requirements to merge into a traffic stream present some of the most challenging environments to navigate for older and vision-challenged drivers. This guideline discusses road-based countermeasures specific to curves and merging (e.g., changing lanes, freeway interchanges) to support older drivers.

Design Guidelines

Long Description. Curves: White edge lines on horizontal curves maintained at high-contrast levels can help older drivers perceive curve geometry, especially under low-light conditions (1). Retroreflective raised pavement markers can improve the visibility of surface delineation on horizontal curves where motorists face increased demands for path maintenance. (1). Post-mounted delineators and/or chevrons can be installed on horizontal curves with appropriate uniform spacing (1). For vertical curves, where a need has been determined for installation or replacement of a device to warn drivers that sight distance is restricted by a crest vertical curve, the 30-in. x 30-in. HILL BLOCKS VIEW sign with an Advisory Speed plaque can be used (1). If a signalized intersection is obscured by vertical curvature in a manner that the signal becomes visible at a preview distance of 8 seconds or less (at operating speed), then in addition to the standard advance signal warning sign, a BE PREPARED TO STOP warning sign and WHEN FLASHING plaque can be used along with a warning beacon interconnected with the traffic signal controller (1). Curve warning pavement markings can be considered as a supplement to curve warning signs at horizontal curves identified as a safety problem (1). High-friction surface treatments can be used on horizontal and vertical curves, at intersections, at on and off-ramps, on bridge decks, locations prone to frequent rain, snow, or ice, or where additional side friction is beneficial (1). Merging: The calculation of letter size requirements for signs at interchanges and on their approaches based on an assumption of a minimum specific ratio of 1 in. of letter height per 30 feet of legibility distance is recommended for new or reconstructed installations and for sign replacement (1). To increase the reading distance of all highway destination signs, it is required by the 2023 MUTCD that mixed-case lettering be used for destination and street names (1). Overhead Arrow-per-Lane guide signs can be used on all new or reconstructed freeways and expressways, whereby the number of arrow shafts appearing on the sign matches the number of lanes on the roadway at the location of the sign (1). Microprismatic retroreflective sheeting can be used on overhead and ground-mounted guide signs to further enhance positive contrast (1). A parallel (rather than a taper) design with long acceleration lanes for the entrance ramp can provide more time for merging drivers to find an opening (1). Improvements to ease the exit process for freeway exits can include high-quality graphics and greater use of sign panels listing several upcoming exits (1). A 48-in. x 30-in. guide sign panel with the legend Freeway Entrance, using a minimum letter height of 8 in., can be consistently used in situations where freeway entrance and exit ramps are adjacent to one another (such as at a partial cloverleaf interchange) and placed as described in the MUTCD (1). Delineation in the vicinity of the exit gore at non-illuminated and partially illuminated interchanges should include, as a minimum, raised pavement markers and retroreflective post-mounted delineators (1). At major freeway interchanges and route splits, route shield markings can be used in the lanes approaching the split to guide drivers to the correct approach lane (1).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Older drivers can have trouble negotiating curves because declining vision changes their ability to see the roadway and judge speed-distance relationships; declining strength makes it more difficult for them to abruptly change directions and shift gears; increased reaction time makes it more difficult for them to safely adjust their driving when approaching unexpected changes in roadway curvature; decreased ability to process large amounts of information makes it more likely that they will miss important warnings about curves ahead; and older drivers with slow reaction times and diminished cognitive abilities might approach curves at excessive speeds (2). Studies have demonstrated that aging drivers are involved in crashes on horizontal curves as a result of driving too fast for the curve or because they were surprised by the curve alignment. However, they are also involved in loss-of-control crashes resulting from an inability to maintain a lateral position throughout the curve because of excessive speed, inadequate deceleration in the approach zone, poor anticipation of vehicle control requirements, and inadequate perception of the demands of the curve (1).

Another major challenge that older drivers face is merging into traffic on fast-moving roads (such as interchanges) and changing lanes while also focusing attention on other vehicles and objects (3). Changing lanes is among the most dangerous driving behaviors overall, with over 250,000 crashes attributed to lane changes each year in the United States (3). Age-related diminished capabilities that primarily contribute to aging driversʼ difficulties at freeway interchanges include losses in vision and information processing ability, which, along with decreased physical flexibility in the neck and upper body can impair visual search, and slowed reaction time to execute vehicle movements, particularly when a sequence of movements such as braking, steering, and accelerating to weave and then exit a freeway is required (1). National database analyses demonstrate that older drivers are disproportionately involved in crashes attributable to highway lane changes, and age-related changes in the ability to control attention have been found to be a stronger factor in lane change errors than age-related changes in vision or stress management (3). One study conducted a statewide analysis of crash involvement ratios and types of violations for drivers in four age groups (26 and younger; 27–55; 56–75; 76 and older) and found that drivers 76 and older were overrepresented as the driver at fault in merging and weaving crashes near interchange ramps and were cited most frequently for failing to yield and for improper use of lanes (1). Similarly, another study evaluating pre-crash maneuvers and contributing factors in aging driver freeway crashes indicated that aging drivers were much more likely than younger drivers to be merging or changing lanes, or passing/overtaking prior to a crash, and that aging driversʼ failure to yield was the most common contributing factor (1). Lastly, in a survey of 692 aging drivers, 25% reported that they stop on a freeway entrance ramp before merging onto the highway, and 17% indicated they have trouble finding a large enough gap between vehicles in which to merge (1).

Design Considerations

According to the Handbook for Designing Roadways for the Aging Population, the intersection of interchange entrance and exit ramps with surface streets can create an environment that is unfriendly and sometimes unsafe for pedestrians (1). Motorists tend to have a low yield rate at these locations and can be traveling at moderately high speeds, which puts vulnerable pedestrians in a compromised state when crossing at these locations (1). Furthermore, there is a need for more research to be performed on specific roadway treatments for pedestrians at interchanges (1).

Cross References

Older Driver Considerations for Markings, Signs, and Lighting

Older Driver Considerations for Intersections—Signs

Older Driver Considerations for Intersections—Pavement Markings and Signals

Key References

OLDER DRIVER CONSIDERATIONS FOR WORK ZONES—SIGNS

Introduction

Construction and work zones are important to consider with respect to aging driver needs because of their potential to violate driver expectancy, which is a key factor that affects the safety and efficiency of all aspects of the driving task (1). Research has shown that older adults respond much more slowly to stimuli that are unexpected, suggesting that they can be particularly disadvantaged by changes in roadway geometry and operations such as those found in construction zones; they are more likely to respond to new traffic patterns in an automatic fashion based on prior experiences, which can lead to more frequent driver errors (1). This guideline discusses road-based countermeasures specific to signage to support older drivers navigating through construction/work zones.

Design Guidelines

Long Description. Signing and advance warning: At construction/maintenance work zones on high-speed roadways (with posted speed limits of 45+ miles per hour) and divided highways, a flashing arrow panel located at the taper for each lane closure can be used (1, 2). A supplemental (portable) changeable message sign (CMS) displaying the one-page (phase) message LEFT (RIGHT, CENTER) LANE CLOSED can be placed 0.5 to 1.0 miles upstream of the lane closure taper or redundant static signs should be used, with a minimum letter height of 8 in. and fluorescent orange retroreflective sheeting, where both the first upstream sign and the second sign encountered by the driver are equipped with flashing warning lights throughout the entire time period of the lane closure (1, 2). To increase the legibility distance of ground-mounted work-zone signs, fluorescent orange may be more effective than beaded high-intensity orange sheeting (1). A minimum specific ratio of 1 in. of letter height per 30 feet of legibility distance can be used (1). Portable changeable message signs: Per the MUTCD, “each message shall consist of no more than two phases” (3). If a message cannot be conveyed in two phases, multiple CMSs and/or a supplemental highway advisory radio message can be used; alternatively, a single phase presenting only the action statement used (1, 2). Each phase of a CMS message can be displayed for a minimum of 2 s (1, 2, 3). The MUTCD states “a unit of information, which is a single answer to a single question that a driver can use to make a decision, should not be more than four words”, “only one unit of information should appear on each line of the CMS”, and “no more than three units of information should be displayed in a message phase” (3). The top line can present the problem, the center line can present the location or distance ahead, and the bottom line can present the recommended driver action. A phase can consist of no more than three lines of a maximum of eight characters per line (3). When a CMS is used to display a message in two phases, the problem and location statements can be displayed during phase 1 and the effect or action statement during phase 2 (1, 2). It is recommended that each message phase communicate a complete thought independent of the other message phase and that each phase makes sense regardless of which phase is read first (3). When a message is composed of two phases and has a higher informational load, “the letter height should be 18 inches, regardless of the speed limit, to optimize legibility distance and available viewing time” (3). Portable CMSs can be elevated to a height sufficient to be seen across multiple lanes of (same-direction) traffic by approaching passenger car drivers (1).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Challenges of navigating construction/work zones. Construction/work zones can pose a specific challenge for older drivers because they are often unexpected and may involve complicated driving maneuvers (2). To safely navigate through a construction zone, drivers must be aware of the conditions ahead and understand the necessary changes in driving behavior (2). Older drivers can find it difficult to read and interpret traffic control devices and react quickly and safely to changing roadway conditions due to functional deficits such as decreased ability to focus attention on important messages when a variety of stimuli are present, increased time necessary to process information from traffic control devices, impaired vision making it difficult to see and read traffic control devices, and increased reaction time making it difficult to react safely when coming upon unexpected traffic conditions (2). In addition, a mail survey of 1,329 American Association of Retired Persons (AARP) members aged 50 to 97 found that 21% of the respondents indicated that they have problems with accurately judging distances in construction zones and they reported additional problems with negotiating congestion/traffic, a lack of adequate warning, narrow lanes, lane closures and lane shifts, and difficulty staying in their lane (2). Further, a crash analysis at 20 case study work-zone locations found that among the most frequently listed contributing factors were driver attention errors and failure to yield the right-of-way, and aging drivers are most likely to demonstrate these deficits (1).

Signing and advance warning in construction zones can be particularly beneficial to older drivers. Increased viewing time leads to reductions in response uncertainty and decreased reaction time for aging drivers (1). Increasing sign conspicuity with treatments such as flashing warning lights, fluorescent orange reflective sheeting, and increased letter height can help older drivers with visual deficiencies as well as help them focus on important information for the environment ahead (2). In addition, providing advance warning signs can help improve driver expectancy by providing adequate notice to drivers describing the condition ahead, the location, and the required response (4).

Portable changeable message signs. The purpose of CMSs is to communicate real-time traffic regulatory, warning, or guidance messages to drivers (4). The conspicuity, content, timing, phasing, and placement of changeable message signs in construction zones are key factors in the attainment of CMS information for older drivers (1, 2). Single-phase messages can reduce the time needed to read and glance away from the roadway (3). In addition, signs that contain too much information, are complicated, or have unfamiliar messages may be difficult for them to read and understand (2). Furthermore, older drivers may not be able to process large amounts of information as efficiently as younger drivers and may need additional time to read and understand the information presented, thereby demonstrating the need for longer viewing time of each message phase presented on a CMS (1, 2).

Design Considerations

Temporary traffic control zones may affect not only older drivers but also older pedestrians. If a construction zone affects the movement of pedestrians, “adequate pedestrian access and walkways shall be provided” with clear delineation (3).

In doing so, construction zones can minimize conflicts between vehicle, equipment, and pedestrian movements and incorporate advance signing when possible (3). Additionally, where pedestrians are routed on temporary pedestrian pathways, providing information in nonvisual formats (such as accessible pedestrian signals with audible tones and/or speech messages, and vibrotactile surfaces) can aid pedestrians with visual disabilities in more safely navigating the temporary pathway (3).

Cross References

Older Driver Considerations for Work Zones—Markings and Channelization

Changeable Message Signs

Presentation to Maximize Visibility and Legibility

Key References

OLDER DRIVER CONSIDERATIONS FOR WORK ZONES—MARKINGS AND CHANNELIZATION

Introduction

Construction and work zones are important to consider with respect to aging driver needs because of their potential to violate driver expectancy, which is a key factor that affects the safety and efficiency of all aspects of the driving task (1). Research has shown that aging adults not only respond much more slowly to stimuli that are unexpected, suggesting that they can be particularly disadvantaged by changes in roadway geometry and operations such as those found in construction zones, but also are more likely to respond to new traffic patterns in an automated fashion, often resulting in more frequent driver errors (1). This guideline discusses road-based countermeasures specific to markings and channelization to support older drivers navigating through construction/work zones.

Design Guidelines

Long Description. Temporary pavement markings: Raised retroreflective pavement markers can be considered for use along detours, temporary roadways, and other changed or new travel-lane alignments. The raised pavement markers can supplement other temporary line markings, or they can substitute for other temporary line markings to enhance visibility of the lines at night, especially in the rain. Delineation of crossovers/ alternate travel paths: Positive barriers in transition zones and positive separation (channelization) between opposing two-lane traffic can be used throughout a crossover, for intermediate- and long-term-duration work zones, and for all roadway classes except residential (1). Side reflectors with cube-corner lenses spaced at a distance (in feet) at no more than the construction zone speed limit (in miles per hour) can be used on concrete channelizing barriers in crossovers [or alternately, the use of retroreflective sheeting on plastic glare-control louvers (paddles) placed in crossovers] (1). For construction/work zones on high-volume roadways, glare-control screens can be mounted on top of temporary traffic barriers that separate two-way motor vehicle traffic, when used in transition and crossover areas, at a spacing of not more than 24 inches. (1). Channelization/ path guidance: The following minimum dimensions or properties for channelizing devices used in highway work zones can be used to accommodate the needs of aging drivers: traffic cones 36 inches. high, with two bands of retroreflective material totaling at least 12 inches. wide for nighttime operations; tubular markers 42 inches. high, with a single band of retroreflective material at least 12 inches. wide for nighttime operations; vertical (striped) panels 12 inches. wide; barricades 12-inch by 36-inch minimum dimension; drums 18 inches. by 36 inches, with high-brightness sheeting for the orange and white retroreflective stripes (1). Where engineering judgment indicates a special need for speed reduction where there is horizontal curvature or through the taper for a lane closure, spacing of channelizing devices at a distance in feet equal to no more than half of the speed limit in miles per hour is recommended (e.g., in a 40 miles per hour zone, space the devices no farther apart than 20 feet) (1). Vertical panels can be 200 to 300 millimeters (8 to 12 inches) in width and be mounted with the top a minimum of 900 mm (36 inches) above the roadway. The height of the panel itself can be at least 600 millimeters (24 inches.). Side reflectors with cube-corner lenses or reflectors (facing the driver) mounted on top of concrete safety shape barriers and related temporary channelizing barriers can be used, spaced (in feet) at a distance no more than the construction zone speed limit (in miles per hour) through a work zone (1). When temporary traffic barriers are placed immediately adjacent to the traveled way, they can be equipped with appropriate channelizing traffic control devices, delineation, and/or other temporary traffic control devices to provide guidance and warning both day and night. (2). Channelizing devices or temporary barriers can be used to separate opposing traffic. (2).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Challenges of navigating construction/work zones. Construction/work zones pose a specific challenge for older drivers because they are often unexpected and may involve complicated driving maneuvers (2). To safely navigate through a construction zone, drivers must be aware of the conditions ahead and understand the necessary changes in driving behavior (2). Older drivers can find it difficult to read and interpret traffic control devices and react quickly and safely to changing roadway conditions due to functional deficits such as decreased ability to focus attention on important messages when a variety of stimuli are present, increased time necessary to process information from traffic control devices, impaired vision making it difficult to see and read traffic control devices, and increased reaction time making it difficult to react safely when coming upon unexpected traffic conditions (2). In addition, a mail survey of 1,329 AARP members ages 50 to 97 found that 21% of the respondents indicated that they have problems with accurately judging distances in construction zones and they reported additional problems in negotiating congestion/traffic, lack of adequate warning, narrow lanes, lane closures and lane shifts, and difficulty staying in their lane (2). Further, a crash analysis at 20 case study work-zone locations found that among the most frequently listed contributing factors were driver attention errors and failure to yield the right-of-way, and aging drivers are most likely to demonstrate these deficits (1).

Temporary pavement markings. The roadway pavement itself is a primary source of information for drivers, which suggests that there is a need for unambiguous pavement delineation patterns in work zones to provide clear guidance, especially at night and under adverse weather conditions, and to accommodate drivers with visual limitations associated with normal aging (1, 2). Research has found that raised pavement markers used for delineation of the centerline and edge lines in construction zones can provide improved wet-weather and nighttime reflectivity and are especially useful when lanes divert from their original paths (1).

Delineation of crossovers/alternate travel paths. Declining functional capabilities of aging drivers can affect their performance as they approach and negotiate a crossover in a work zone (1). A crossover requires a change in direction and perhaps a reduction in speed, which may benefit from advance warning of the lane and speed reduction, conspicuous and unambiguous delineation/channelization in the transition zone, and conspicuous separation of opposing traffic via the use of positive barriers, device spacing, reflectors, and/or glare-control screens (1).

Channelization/path guidance. Countermeasures for channelization systems, such as cones, tubular markers, vertical panels, barricades, and drums, can assist older drivers navigating construction zones. Because of decreased visual capabilities, challenges processing large amounts of information, and decreased physical capacity to perform abrupt driving maneuvers, older drivers need conspicuous and unambiguous traffic control devices to help guide them through temporary traffic control zones (2).

Design Considerations

Blocked routes, alternate crossings, and sign and signal information should be communicated to visually impaired pedestrians by providing devices such as audible information devices or barriers and channelizing devices that are detectable to the pedestrians traveling with the aid of a long cane or who are visually impaired (4). When channelization is used to delineate a pedestrian pathway, a continuous detectable edging should be provided throughout the length of the facility such that pedestrians using a long cane can follow it (4).

Cross References

Older Driver Considerations for Markings, Signs, and Lighting

Visibility of Lane Markings

Key References

OLDER DRIVER CONSIDERATIONS FOR INTERSECTIONS—LEFT TURNS

Introduction

According to the FHWAʼs Handbook for Designing Roadways for the Aging Population, the single greatest concern in accommodating aging road users, including drivers and pedestrians, is the ability of these individuals to negotiate intersections safely (1). Intersections pose a particular safety problem for older drivers because of the need for rapid decision-making, quick reactions, and accurate judgments of speed-distance relationships, all of which become generally more difficult as people age (1, 2). Accident data is congruent with this, as it demonstrates that drivers 65 years and older are involved in a higher percentage of injury and fatal accidents at intersections than other age groups (1, 2). In addition, left turns at intersections pose specific challenges to aging individuals (1, 3). This guideline discusses road-based mitigation strategies to support older drivers navigating left turn maneuvers at intersections.

Design Guidelines

Long Description. Dedicated left-turn lanes and channelization: Turn path markings can be installed (2). Left-turn lanes can be positively offset at least 4 feet to the left of the opposing left-turn lane to achieve the desired sight distance for the left-turning driver. This can provide a margin of safety for aging drivers who do not position themselves to the far left within the lane and within the intersection before initiating a left turn (1, 2). On undivided highways where pavement width allows, this positive offset can be provided using solid channelizing lines to form a parallel or tapered island between the left-turn lane and the adjacent through lane (2). Raised channelization with sloping curbs may be used instead of channelization by pavement markings alone (flush) for left- and right-turn lane treatments at intersections on all roadways with operating speeds of less than 45 miles per hour (1). Protected left-turn signal phasing: Protected-only left-turn phasing can be used for all left-turning movements when appropriate. Protected- only left-turn phasing can be considered where minimum intersection sight distance requirements are not achieved with offset left-turn lanes or other geometric design features, or where a pattern of permissive left-turn crashes occurs (1). Intersection angle (skew): In the design of new facilities or redesign of existing facilities where right-of-way is not restricted, all intersecting roadways can meet at a 90-degree angle (1). In the design of new facilities or redesign of existing facilities where right-of-way is restricted, intersecting roadways can meet at an angle of not less than 75 degrees (1).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

The figures below show examples of positive offset for left-turn lanes and intersection angle (1, 2).

Long Description.

The first illustration shows a positive offset for left turn lanes. The second illustration shows an intersection with a 90-degree angle. The third illustration shows an intersection with a 75-degree angle.

Discussion

Challenges of navigating intersections and left turns. Because of the perceptual, motor, sensory, and physiological changes associated with aging, there are difficulties that older roadway users experience when maneuvering through intersections, particularly when making left turns (2). Older drivers experience numerous operational problems when navigating intersections, including incorrect positioning in the turn lane or positioning in the wrong lane during intersection approach, inability to accurately judge the distance of oncoming vehicles, confusion and vision problems increasing potential wrong-way maneuvers on left turns, indecision about which lane to use at unfamiliar or complicated intersections, lack of understanding when it is safe to cross the roadway at signalized intersections, and limited head mobility to view intersecting traffic (1, 2).

Dedicated left-turn lanes and channelization can be effective countermeasures for the challenges intersections pose for older drivers (1, 4). One study found that adding a dedicated left-turn lane resulted in a 13% greater reduction in injury crashes among licensed drivers 65 and older compared to drivers aged 25–64 (5). Having multiple left-turn lanes at an intersection and, relatedly, providing offset left-turn lanes at intersections, can reduce the potential for crashes between vehicles turning left from a major road and through vehicles on the opposing road because of a driverʼs restricted view of oncoming traffic (1, 6). Left-turn lanes with raised channelization with sloping curbs can also be beneficial (1), however, to realize the safety benefits channelization can provide, it is important to ensure the visibility of raised surfaces for aging drivers with diminished vision so that these road users can detect the channelizing devices and select their paths accordingly (1). Another benefit of channelization in general, for drivers and pedestrians, is that it serves to simplify a complex situation, and the channelization of an existing intersection might enhance the safety and mobility of aging pedestrians and drivers (1).

Protected left-turn signal phasing at large and/or complex intersections can support all driversʼ driving performance by halting oncoming traffic and providing more time to complete the turn (1, 6). Extant literature has found that older drivers prefer to turn left on a protected arrow phase, rather than making permissive-phase turns (1, 6). Further, one study found that the most challenging aspect of intersection negotiation for older drivers is performing left turns during the permissive signal phase (1).

Intersections with acute intersection angle (skew) pose particular problems for aging drivers, as these intersections require drivers to turn their heads further than would be required at right-angle intersections, which can be difficult for older drivers with diminished physical capabilities, making it more difficult for them to recognize conflicts and determine appropriate gaps (1, 6). Decreasing the intersection angle (skew) can make detection of and judgments about potential conflicting vehicles on crossing roadways much more difficult for drivers (1). In addition, the amount of time required to maneuver through the intersection increases for both vehicles and pedestrians due to the increased pavement area (1). While there is some inconsistency concerning the degree of skew that can be safely designed into an intersection, the research findings reinforce the desirability of providing a 90-degree intersection geometry or at least a minimum of 75 degrees (1, 6).

Design Considerations

Turning vehicles at intersections can also pose challenges for aging pedestrians due to the loss of peripheral vision and the increased likelihood of not detecting approaching and turning vehicles from the side (1). Further, one study found that aging pedestrians were overrepresented in both right- and left-turn vehicle–pedestrian crashes (1).

Cross References

Left-Turn Lanes at Non-Signalized Intersections

Sight Distance at Left-Skewed Intersections

Sight Distance at Right-Skewed Intersections

Key References

OLDER DRIVER CONSIDERATIONS FOR INTERSECTIONS—ROUNDABOUTS

Introduction

Reconfiguring existing or new intersections as roundabouts can help reduce the frequency and severity of crashes at intersections due to lower vehicle speeds, safer merges, more opportunities to correctly judge and enter gaps, reduced conflict points, and eliminating some of the most complicated aspects of traditional intersections (e.g., left turns) (1, 2, 3, 4). Roundabouts can be an effective treatment for at-grade intersections (3) and can meet an extensive range of traffic conditions because they are adaptable in size, shape, and design (5). Further, the FHWA considers roundabouts to be a “Proven Safety Countermeasure” (1, 3). This guideline discusses road-based mitigation strategies to support older drivers and pedestrians navigating through roundabouts.

Design Guidelines

Long Description. Number of lanes: Unless required by operational needs, roundabout installations could be limited to one-lane entrances and exits and one lane of circulating traffic in order to make them easier to negotiate (1). Pedestrian crossings: Pedestrian crossings at single-lane roundabouts can be set back a minimum of 25 feet from the yield lines and include a crossing island of at least 6 feet in width (1). Splitter and central islands: To control for wrong-way movements, calm traffic, and provide a pedestrian refuge for all roundabout categories, raised splitter islands can be used, as opposed to pavement markings, to delineate the channelization. The pedestrian crosswalk area can be designed at street level (crosswalk cut through a splitter island) (1). The sides and tops of curbs on the splitter islands and the central island can be treated with retroreflective markings and be maintained at a minimum luminance contrast level as follows: At roundabouts with overhead lighting, maintain a contrast of 2.0 or higher and at roundabouts without overhead lighting, maintain a contrast of 3.0 or higher (1). Signs: An Advance Roundabout Warning sign (W2-6) can be used on all approaches to a roundabout (1). A Roundabout Directional Arrow sign (R6-4 series) can be used to direct traffic counter-clockwise around the central island. This sign display can be placed on the central island in direct view of a driver’s entry point (if different than at the centerline of the approaching roadway) (1). The Roundabout Circulation Plaque (R6-5P) can be placed immediately below the R1-2 YIELD sign on both sides of the road at each entrance to a roundabout (1).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 3 on the scale.

The figures below demonstrate examples and placement of a roundabout directional arrow sign and roundabout circulation plaques (1).

Long Description.

In the first illustration, the roundabout arrow signals are placed around the central island. The second illustration shows two signs placed on both sides of an exit road; a sign in between the approaching lanes with three curved arrows representing the roundabout that is labeled as optional, and a yield sign on the side of the road approaching the roundabout.

Discussion

While research to date is limited, extant literature suggests that roundabouts can provide solutions to aging drivers who may have difficulty judging speeds and gaps, understanding operational rules at complex intersections, and maneuvering through turns (1). For older drivers, the advantages of roundabouts include providing more time to judge, adjust speed, make decisions, and react, which simplifies decision-making due to one-way operation and yield-at-entry, reducing the need to look over oneʼs shoulder and to judge closing speeds and gaps in fast traffic, eliminating the left turn, improving maneuverability due to a larger curb radius, reducing vehicle speed entering the roundabout, and reducing conflict points (1, 4). Roundabouts can provide drivers with shorter braking distances and longer timeframes to make decisions, and even if a driver makes a mistake and chooses a gap that is too short, potential collisions are easier to avoid (1). Single-lane roundabouts exhibit some of the fewest total and severe crashes compared with other intersection forms (4). Pedestrian safety may also be improved, especially with single-lane roundabouts, due to shorter crossing distances, increased driver ability to react and yield to pedestrians, fewer potential conflicts with vehicles, and lower vehicle speeds (1, 4).

Splitter islands—raised or painted areas that physically separate entering traffic from exiting traffic and define the entry angle—are geometric features that deflect and slow entering traffic and can also serve as a safety zone for pedestrians (1). Splitter islands provide drivers with advance detailed information about what to expect in the roundabout and contribute to the safety of roundabout navigation (1). One study presented in the FHWA older driver handbook found that the use of the roundabout advance warning sign, augmented with a symbol representing the center island, would help aging drivers feel more comfortable, confident, and/or safe in roundabout navigation (1, 2). Results indicated that aging drivers also preferred the use of lane control signs designating the intended destinations for each lane (for multilane roundabouts) that were accompanied by a black solid circle representing the central island and text indicating lane position (see figures below) (1). The researchers suggested that for multilane approaches to roundabouts, signs should be designed to ensure that drivers choose the proper lane for their destination before reaching the roundabout, and once in that lane, they should be able to navigate the roundabout and exit to their destination without having to change lanes while in the circular roadway of the roundabout (1).

Long Description.

The left lane shows a curved arrow around a circle with exiting arrows. The right lane shows a curving road with exiting arrows.

Design Considerations

Roundabout implementation has accelerated in the last 30 years in the United States, with an estimated 8,800 roundabouts installed through 2021 (4). However, limited naturalistic research examining roundabouts in general, and their use by older drivers in particular, has been conducted to date. This topic would benefit from further research to assess the efficacy of various elements of roundabouts, such as lane-use control signs, directional signs, yield signs, and exit signs.

Cross References

Roundabouts, Chapter 12

Markings for Roundabouts

Key References

OLDER DRIVER CONSIDERATIONS FOR INTERSECTIONS—SIGNS

Introduction

Revisions to traffic engineering elements can be made to assist older individuals in navigating intersections more comfortably. This guideline discusses road-based mitigation strategies specific to signs at intersections.

Design Guidelines

Long Description. Minimum letter heights of 6 inches for uppercase letters and 4.5 inches for lowercase letters may be used on ground-mounted street-name signs (MUTCD D3-1) on all roads where the posted speed limit is at or below 25 miles per hour(1). On all roads where the posted speed limit is greater than 25 miles per hour, letter heights of 8 inches for uppercase letters and 6 inches for lowercase letters can be used (1). Overhead-mounted street-name signs can be used at major intersections as a supplement to ground-mounted street-name signs. Minimum letter heights of 12 inches for uppercase letters and 9 inches for lowercase letters are recommended by the MUTCD (1). Wherever an advance intersection warning sign is installed (MUTCD W2 series), it can be accompanied by an advance street-name plaque (W16-8P or W16-8aP) using minimum letter heights of 6 inches for uppercase letters and 4.5 inches for lowercase letters. (1). Where an advance traffic control sign (MUTCD W3 series) is installed on a multilane approach, an advance street-name plaque (W16-8P or W16-8aP), using the same minimum letter heights described above, can be considered (1). In the absence of an advance intersection warning sign or advance traffic control sign (with accompanying advance street-name plaque), advance street-name signs (MUTCD D3-2) for major intersections can be used, with turn bays to provide adequate preparation time for any lane change and/or turning maneuvers (1). When different street names are used for different directions of travel on a crossroad, the names can be separated and accompanied by directional arrows on both advance and intersection street-name signs (1). For ground-mounted street-name signs installed at intersections in areas of intensive land use, complex design features, and heavy traffic, prismatic retroreflective sheeting that provides for high retroreflectance can be used to provide increased sign conspicuity and legibility for aging drivers (1). The use of standard size (30-inches for single lane applications, 36-inches for multilane applications) STOP (R1-1) and standard size (36-inches for single lane applications, 48-inches for multilane applications, 60-in for freeway applications) YIELD (R1-2) signs, as a minimum, is required by the 2023 MUTCD wherever these devices are implemented, with the option of using larger R1-1 (36-inches for single lane applications, or 48-inches in any location) signs where engineering judgment indicates that greater emphasis or visibility is required (1). A minimum sign background (red area) retroreflectivity level [i.e., coefficient of retroreflection (RA)] for STOP (R1-1) and YIELD (R1-2) signs is as follows: 12 cd/ lux / meter squared for roads with operating speeds lower than 40 miles per hourand 24 12 cd/ lux / meter for roads with operating speeds of 40 miles per houror higher. Signs with an RA below these levels can be replaced (1). The use of a 30-inches x 18-inches supplemental warning sign panel (MUTCD W4-4P) mounted below the STOP (R1-1) sign, can be used for two-way stop-controlled intersection sites selected on the basis of crash experience, where the sight triangle is restricted, and wherever a conversion from four-way stop to two- way stop operations is implemented (1). A STOP AHEAD sign (MUTCD W3-1) can be used where the distance at which the STOP sign is visible is less than the AASHTO stopping sight distance at the operating speed, plus an added preview distance of at least 2.5 seconds (1).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Multiple sign treatments, such as size, placement, brightness, and redundancy, can be made to assist older drivers in navigating intersections (1, 3). Increasing the conspicuity of ONE WAY, WRONG WAY, and DO NOT ENTER signs by using larger-than-standard (MUTCD) size signs, and using retroreflective sheeting on these signs that provides for high brightness at the wide observation angles typical of the sign placements and distances at which these signs are viewed will be of benefit to drivers, especially those with reduced visual and attentional capabilities (1). At intersections with wide medians or offset left-turn lanes, large signs can be used for greater legibility and emphasis for messages warning against wrong-way traffic movements (2). The LEFT TURN YIELD ON GREEN sign may be used to remind drivers of the right-of-way rule for left turns at signalized intersections (2), and educational plaques can be installed at signalized intersections to help explain the traffic signal operation and present a warning to watch for turning vehicles (2). At intersections where drivers might have trouble positioning themselves in the correct lane, intersection lane control signs can be mounted overhead on a signal mast arm or span wire and be placed over the lane (or a projection of the lane) to which it applies (1, 2). Lastly, advance street-name signs and lane-use signs assist left- or right-turning drivers by confirming locations well before the turn and providing early guidance to drivers so that they do not find their vehicle in the wrong lane at an intersection (3). Advance street-name signs placed upstream of the intersection at midblock locations are also recommended (2).

Design Considerations

Educational signs and plaques can be used at signalized intersections to help improve pedestrian understanding of signals (2, 4). These signs can be installed at crosswalks to help explain the traffic signal operation, present a warning to watch for turning vehicles, inform pedestrians of clearance time, and tell them which button to push to cross the street; see the figure below for examples of signs included in the MUTCD (1, 2, 4).

Long Description.

The first sign, R 10–3 d has four sections. The first has a graphical pedestrian walk signal and reads Start Crossing to median, Watch for Vehicles. The next section has a flashing pedestrian don’t walk signal. It reads Don’t Start; Finish Crossing if Started. The next section has a steady pedestrian don’t walk signal. It reads Don’t Cross. The next section reads Push Button to Cross and shows an arrow. The second sign, R 10–3 e has five sections. The first has a graphical pedestrian walk signal and reads Start Crossing, Watch for Vehicles. The next section has a flashing pedestrian don’t walk signal followed by a sign displaying the number 08. It reads Don’t Start; Finish Crossing if Started; Time remaining to finish crossing. The next section has a steady pedestrian don’t walk signal. It reads Don’t Cross. The next section reads Push Button to Cross and shows an arrow. The third sign, R 10–3 f, has four sections. The first has a graphical pedestrian walk signal and reads Start Crossing to median, Watch for Vehicles. The next section has a flashing pedestrian don’t walk signal. It reads Don’t Start; Finish Crossing if Started. The next section has a steady pedestrian don’t walk signal. It reads Don’t Cross. The next section reads Push Button to Cross Maple Drive and shows an arrow. The fourth sign, R 10–3 g, has four sections. The first has a walk signal displaying the word Walk and reads Start Crossing, Watch for Vehicles. The next section has a flashing pedestrian don’t walk signal that displays the words Don’t Walk. It reads Don’t Start; Finish Crossing if Started. The next section has a steady pedestrian don’t walk signal. It reads Don’t Cross. The next section reads Push Button to Cross Maple Drive and shows an arrow.

Cross References

Signalized Intersections, Chapter 11

General Principles for Sign Legends

Key References

OLDER DRIVER CONSIDERATIONS FOR INTERSECTIONS—PAVEMENT MARKINGS AND SIGNALS

Introduction

Revisions to traffic engineering elements can be made to assist older individuals in navigating intersections more safely. This guideline discusses road-based mitigation strategies specific to pavement markings and signals at intersections.

Design Guidelines

Long Description. Pavement markings: In addition to edge lines on the road surface alongside medians and island curbs, helpful markings could include painted curb markings on the vertical face of curbs and the top surface of the curbs can be marked with retroreflectorized raised pavement markers, object markers, signs, or delineators (1, 2). Where raised channelization is implemented at intersections, the median and island curbsides and curb horizontal surfaces can be treated with retroreflectorized markings, such as edge lines, painted curbs, or raised pavement markers, and be maintained at a minimum luminance contrast level as follows: With overhead lighting, a contrast of at least 2.0. Without overhead lighting, a contrast of at least 3.0 (1). Supplemental pavement markings on approaches to stop-controlled or yield-controlled intersections can be used where engineering judgment indicates a special need due to sight restrictions, high approach speeds, or a history of ran-stop-sign crashes (1). Transverse pavement striping or rumble strips may also be considered where high approach speeds are a concern (1). The consistent posting of lane-use control signs (MUTCD R3 series), along with application of lane-use arrow pavement markings at a preview distance of at least 5 s (at operating speed) in advance of a signalized intersection is recommended, regardless of the specific lighting, channelization, or delineation treatments implemented at the intersection (1). Signals: Visibility and conspicuity of the traffic signal may be increased by a maintained performance level of 200 cd for peak intensity for both 8-inches and 12-inches signals and the use of 12-inches signals in all cases except the few limited situations in which the MUTCD allows the use of 8-inches signals (1). An all-red clearance interval can be consistently implemented, with length determined according to the Traffic Control Devices Handbook (5). A backplate can be used on signal faces viewed against a bright sky or a bright or confusing background (2). Use backplates with traffic signals on all roads with operating speeds of 40 mi/h or higher. The use of backplates with signals is also recommended on roads with operating speeds lower than 40 mi/h where engineering judgment indicates a need due to site history, the potential for sun glare problems, or other variables (1, 2). Yellow retroreflective borders may be used as an option to improve visibility of the illuminated face of the signal. The yellow retroreflective strip should have a minimum width of 1 inches, a maximum width of 3 inches, and be placed along the perimeter of the face of a signal backplate to project a rectangular appearance at night (1). At intersections with high pedestrian volume and high turning vehicle volume, a leading pedestrian interval of three seconds or more can be helpful because it allows slower walkers to cross at least one roadway lane before conflicting turning vehicles are released (2). Blank-out or changeable message “no right turn” (symbolic) or NO TURN ON RED (text) signs can be used in conjunction with the leading pedestrian interval to restrict turns across the crosswalk during certain portions of the signal cycle (2).

Long Description. A scale from 0 to 6 where 0 represents ‘Based Primarily on Expert Judgment,’ 6 represents ‘Based Primarily on Empirical Data,’ and 3 represents ‘Based Equally on Expert Judgment and Empirical Data.’ This guideline ranks a 5 on the scale.

Discussion

Pavement markings at intersections become more important to drivers as they age (1) and can be used to improve the conspicuity of various roadway elements. Materials and devices typically used to identify roadway edges, curbs, medians, and obstacles include retroreflective paint or tape, raised pavement markers (RPMs), post-mounted delineators, object markers, and chevron signs (1). To enhance safety at intersections for older drivers, turn path markings should be installed, especially for complex situations such as single and dual left-turn lanes at intersections; intersections with acute angle turns, especially left turns; side-by-side entrance and exit ramps at partial cloverleaf interchanges; acute angle entrance ramps at diamond interchanges; and other locations where crash experience or operational observations suggest that older drivers may experience difficulties negotiating turning movements (2). In addition to edge lines on the road surface alongside the medians and island curbs, helpful markings could include painted curb markings on the vertical face of curbs, and retroreflectorized RPMs, object markers, signs, or delineators on the top surface of the curbs (1, 2). Lastly, advance pavement-marking messages can be particularly beneficial to aging drivers whose peripheral vision and sign-reading skills may be limited, but who may still respond to messages painted on the pavement (3).

Traffic signal visibility and conspicuity are often associated with their intensity (daytime and nighttime), size, color, backplate, depreciation, and placement (1, 3). Using a larger signal lens provides motorists with more time to determine the signal color and make the correct response (1). In addition, placing or relocating signals to be overhead near the center of the travel lane can increase a signalʼs conspicuity by placing it within the useful field of view, which can decrease as people age (3). To enhance the visibility and conspicuity of traffic signals, a backplate could be used on signal faces viewed against a bright sky or a bright or confusing background (1, 2, 3). Lastly, providing longer clearance intervals at signalized intersections and/or an all-red clearance interval could be implemented to accommodate slower perception-reaction times of older drivers (1, 4).

Design Considerations

Aging pedestrians also face a variety of challenges when navigating through intersections, including decreased visual acuity; increased risk of falls; slower gait, shorter steps, and slower reaction time requiring longer time for pedestrian crossing; greater likelihood to spend more time at the curb, delay before crossing, a need for longer gaps between vehicles, and more time to cross the road; and a diminished ability to detect approaching vehicles in enough time to take evasive action (1, 2). Countermeasures to assist older pedestrians at intersections can include providing more crossing time, a leading pedestrian interval of at least three seconds and an adjacent pedestrian refuge island conforming to MUTCD (6) and AASHTO (7) specifications, and allocating a crosswalk where the right turn is channelized approximately one car length from the yield line for the intersection (1, 2). Countdown pedestrian signals can be installed at all signalized intersections where pedestrian signals are warranted (1) and the TURNING TRAFFIC MUST YIELD TO PEDESTRIANS sign may also be used if pedestrian crosswalks are marked (2).

Cross References

Visibility of Lane Markings

Design Challenges for Older Pedestrians

Key References