CHAPTER 2

Background

Need for Tactile Wayfinding

Wayfinding is possibly the greatest challenge in the urban environment for pedestrians with vision impairments. It requires knowing where they are in relationship to their surroundings (orientation), knowing how to get to a desired point of interest (navigation), and being able to travel to that point of interest safely and efficiently (mobility) (Virgili and Rubin 2010, Parker et al. 2021).

Tools commonly used by pedestrians with vision disabilities to assist with wayfinding are long canes and guide dogs (Sight Scotland 2023):

• Long canes are used to detect objects in the traveler’s path, including potential hazards, obstacles, and wayfinding cues. Depending on the cane tip used and the user’s technique, the cane can be used by rolling, tapping, or sweeping from side to side. The cane is approximately as tall as a person’s breastbone, so in use it is always one or two steps ahead of the user.
• Identification canes (ID canes), shorter and often lighter-weight than long canes (approximately as tall as the user’s waist), are sometimes used by pedestrians with low vision to indicate to other people that they have a vision disability. ID canes can also be used to confirm drop-offs such as curbs and stairs, or to help explore the environment.
• Guide dogs are fitted with a harness and handle the user holds. A guide dog is trained to walk in a straight line and only deviates if needed to avoid an obstacle or when directed by its owner. The owner needs to tell the dog where to go, when to turn, and when to cross a street. The dog is usually on the handler’s left side.

Elements of the built environment, such as building faces, landscaping, and street curbs, provide cues that both cane users and guide dog users can use to follow a path (Bentzen et al. 2021). However, there are many situations in an urban environment where additional accessible wayfinding information is needed to help pedestrians with vision disabilities navigate. Figure 3 provides examples of common situations that present wayfinding challenges.

A variety of technologies are being developed to provide wayfinding assistance to pedestrians with vision disabilities, such as those described by Parker et al. (2021). However, not all pedestrians with vision disabilities have access to these technologies, can use them, or will have a functioning device at the time they need them. Just as there continues to be a need for guide signs in an era where GPS-enabled devices can provide routing information, there remains a need to provide basic physical wayfinding information, and TWSIs remain an important way to provide wayfinding information. When well implemented, TWSIs can supplement other tactile and audible cues for wayfinding for most travelers without the need for them to obtain, maintain, and effectively use any technology.

Types of TWSI

TWSI is a generic term that refers to different tactile surfaces. This guide discusses three types of TWSI (DWSs, TDIs, and TWDs), each with a unique form that conveys a specific message to pedestrians with vision disabilities based on their application in the surrounding environment. These have all been identified through extensive human factors research in the United States and were found to be highly detectable underfoot and by long cane, and highly discriminable and identifiable underfoot.

Detectable Warning Surface (DWS)

DWSs are used in the following situations to indicate hazards along a pedestrian access route, as specified in 36 CFR Part 1190 (commonly referred to as the final Public Right-of-Way Accessibility Guidelines, PROWAG, www.access-board.gov/prowag/#table-of-contents):

• Perpendicular and parallel curb ramps and blended transitions at pedestrian street crossings
• Boundaries of pedestrian refuge islands that are 6 ft in width or wider
• Pedestrian at-grade rail crossings not located within a street
• Transit boarding platforms raised above standard curb height, where the edges of the boarding platform are not protected by screens or guards
• Sidewalk- or street-level transit stops for rail vehicles, where the side of the boarding and alighting areas facing the rail vehicles is not protected by screens or guards
• Pedestrian circulation paths at driveways controlled with stop or yield control or traffic signals

A DWS consists of a square or radial grid of truncated domes. PROWAG permits a range of minimum and maximum dimensions; the typical ranges are illustrated in Figure 4. 36 CFR Part 1190 Section R305 specifies these dimensions along with exceptions to the typical ranges. The DWS indicates to pedestrians with vision disabilities that they should stop, determine whether there is a vehicular way or platform edge in front of them, and prepare to cross or board (Kittelson & Associates, Inc. et al. 2023). Figure 5 shows example applications at a roundabout, where DWSs are used on the street side of both curb ramps and on both sides of the splitter island (pedestrian refuge).

Tactile Direction Indicator (TDI)

TDIs are used to indicate a route that can be followed. There are no established U.S. standards for TDIs at present, but many U.S. transit station applications have conformed to ISO 23599:2019

(ISO 2019), the international standard for a guidance pattern. The surface consists of a strip of parallel raised flat-topped elongated bars, as shown in Figure 6. The orientation of the bars relative to the direction of travel and the width of the strips of bars can be used to convey different messages.

Example TDI applications are shown in Figure 7. These include:

• Guide bars: a 12-in.-wide (300 mm) TDI strip with the raised bars oriented parallel to the direction of travel is used to indicate an unobstructed path of travel.
• Sidewalk alert bars: a 24-in.-wide (600 mm) TDI strip extending across the sidewalk, with the raised bars oriented perpendicular to the direction of travel on the associated crosswalk, is used to indicate the location of a noncorner crosswalk across a street or bicycle lane, or the location of a bus stop. This application significantly improves visually impaired pedestrians’ ability to locate hard-to-find crosswalks and bus stops, such as those not located at a corner, and improves the accuracy of aligning to cross (Bentzen et al. 2022). Orienting the bars perpendicular to the direction of travel on the crosswalk means the bars are parallel to the direction of travel on the sidewalk, which requires less effort and results in less instability when persons with reduced mobility cross the surface (Bentzen, Scott, Emerson, et al. 2020).
• Alignment bars: a 24 in. square (600 mm) of TDI bars, with the raised bars oriented perpendicular to the direction of travel on the associated crosswalk, has been shown to significantly improve the accuracy of visually impaired pedestrians aligning themselves to cross (Bentzen et al. 2022). When used at crossings at intersections, the TDI square is placed adjacent to the DWS farthest from the center of the intersection (Kittelson & Associates, Inc. et al. 2023).
• Transit door location bars: a 24 in. × minimum 36 in. rectangle (600 × 900 mm) of TDI bars, with the shorter edge placed along the curbline or platform edge DWS, is used to indicate boarding locations.

Tactile Warning Delineator (TWD)

The TWD is a relatively new type of TWSI in the United States that is formed by a raised trapezoidal surface 0.75 in. (20 mm) high. TWDs are used to indicate that a hazard exists at the same

grade on the opposite side of the surface and that no crossing point exists along the length of the TWD. This is an important distinction from DWSs, which indicate that a hazard exists on the opposite side of the surface but that the surface can be crossed when the pedestrian determines it is safe to do so. In contrast, a TWD indicates to pedestrians with vision disabilities that they should not cross the surface because of the risk of a crash with a bicycle or motor vehicle on the other side (Kittelson & Associates, Inc. et al. 2023).

No U.S. standards have been established yet for TWDs. Figure 8 shows the surface dimensions used in a test of TWDs in San Francisco (Bentzen, Scott, and Myers 2020), while Figure 9 shows an example application of a TWD to mark the boundary between adjacent bicycle and pedestrian facilities at the same grade. Initial research (Bentzen, Scott, and Myers 2020) indicates that TWDs are highly detectable underfoot or with a long cane, are crossable by people with mobility impairments using a variety of aids, and have no adverse consequences for bicyclists under wet or dry conditions.

Detectability and Discriminability

Two essential elements of TWSIs are detectability and discriminability. Tactile surfaces need to be readily detectable by cane, underfoot, and by visual contrast to accommodate the different ways pedestrians with vision disabilities navigate. Underfoot detectability is particularly

important, as most pedestrians with vision disabilities do not use long canes (Elliott et al. 2017). Because different types of TWSIs convey different messages, they also need to be discriminable from each other so the message being conveyed is correctly understood.

Detectability

In general, TWSI detectability depends on the spacing between the raised elements compared to the top width of the raised element, the height of the raised element, and the TWSI’s overall coverage area. Raised elements spaced closer together are less detectable than those farther apart, but even otherwise detectable surfaces may be missed when pedestrians with vision disabilities approach a TWSI perpendicular to its length if the TWSI’s width (i.e., the dimension facing the approaching direction of travel) is such that people inadvertently step over it. Differences between TWSI materials and the surrounding surfaces that result in differences in sound and/or resiliency between the two surfaces enhance detectability.

Surface Width

Research has consistently found that a TWSI is detectable when it is at least 24 in. (600 mm) wide in the direction of travel across the surface. This result is due to pedestrians’ natural gait and stride length. Surfaces less than 24 in. wide may be more likely to be stepped over and missed when approached perpendicularly or at an obtuse angle. In contrast, blind participants stopped approximately 90% of the time without stepping beyond the DWS when the surface was about 24 in. wide in the direction of travel across it (Peck and Bentzen 1987, Mitchell 1988, Tijerina et al. 1994, Hughes 1995, O’Leary et al. 1996, Bentzen and Myers 1997, Fujinami et al. 2005). However, more recent research in San Francisco suggests that where it is not critical that pedestrians with vision disabilities come to a stop without stepping beyond a TWSI, such as when crossing a TDI path, a smaller width may still enable good detection (Bentzen, Scott, and Myers 2020).

Raised Element Dimensions

Proportions between three key dimensions of the surface’s raised elements determine whether a TWSI will be detected, provided the surface is sufficiently wide:

• Height. The height of TWSIs used in practice, and required by most standards, is around 0.2 in. (5 mm). This height has been shown to be detectable and discriminable by pedestrians with vision disabilities, while not impeding persons with reduced mobility (Bentzen, Nolin, Easton, et al. 1994, NITE 1998, Sawai et al. 1998, NITE 2000). The height of the raised element is particularly important in outdoor settings, where the surrounding pavement is less likely to be uniformly smooth.
• Top width or diameter. Research indicates that raised element top widths or diameters of 18–35 mm are detectable (NITE 1998, Sawai et al. 1998).
• Spacing between raised elements. Research indicates that a center-to-center spacing of 60–70 mm (domes) and 75–86 mm (bars) is detectable (NITE 1998, Sawai et al. 1998).

Both U.S. transportation agency experience and international experience (e.g., Danish Road Directorate 2013) are that grooves cut into a surface are difficult to detect either with a cane or underfoot.

Visual Contrast

While TWSIs are intended to be detected primarily based on tactile information conveyed through the geometry of their surface patterns, most people who are legally blind are not fully blind. It is therefore the consensus in U.S. and international standards and guidance that TWSIs should have high visual contrast with surrounding surfaces.

Jenness and Singer (2006) conducted a highly controlled study to support the development of a detailed U.S. standard regarding DWS color and contrast. The luminance contrast between the DWS and the simulated sidewalk was a strong predictor of detection and conspicuity rating of the DWS; however, even with high luminance contrast, dark DWSs on dark sidewalks were detected less often than would have been predicted based on luminance contrast alone. Red and yellow colors were more detectable and conspicuous than white, black, or gray. Reflectance also predicted detection and conspicuity; lighter colors were better than darker colors, and DWSs similar in color to the adjacent surface were seldom detected.

Jenness and Singer (2006) recommended that DWS color choice be determined by luminance contrast with the adjoining surface, light on dark or dark on light, and that combinations where the reflectance of the lighter color was less than 10% should not be used. “Federal yellow” (Pantone 109u) was recommended where the desire was to have a single uniform color for DWSs; this color had a high conspicuity rating across different levels of luminance contrast. Yellow is especially effective in association with dark sidewalks. Where sidewalk surfaces are light-colored, a good choice for both detection and conspicuity is a dark brick red (red-orange). Bentzen, Nolin, and Easton (1994) previously found that a federal yellow DWS was highly detectable on new white concrete with contrast as low as 40%.

Several Japanese studies support the need for both color contrast and improved ambient lighting to increase luminance contrast. Yellow was found to have the highest detection rate at low light levels (Mitani et al. 2007, Mitani et al. 2009, Mitani et al. 2011).

Discriminability

When TWSIs are used together as a system, they must be highly discriminable and identifiable because each type calls for a different response. The seminal research testing the discriminability of TWSI patterns took place in Japan in studies conducted primarily by the National Institute of Technology and Evaluation (NITE), which tested 81 combinations of nine truncated-dome surfaces and nine raised-bar guidance surfaces of different geometries (NITE 1998). This is the only known research that systematically varied the dimensions of raised-bar and truncated-dome elements, as well as the spacing between the raised elements, to identify optimal geometries for each surface type such that each pattern type (domes or bars) was not only detectable but also identifiable from the other underfoot.

Height also plays a role in discriminating TWSIs. Japanese research concluded that TWSIs must be 4–5 mm high for good detectability and discriminability (NITE 1998, Sawai et al. 1998, NITE 2000). In the United States, DWSs are required to be 5 mm high based on research that also found that when DWSs are installed in association with a rough surface, they are less detectable than when installed on smoother surfaces (Bentzen, Nolin, Easton, et al. 1994). This principle is well accepted internationally (e.g., ISO 23599), although some research suggests that the height required for good detectability and discriminability might be somewhat less when installed in association with a smooth surface (Nakamura et al. 2011).

Detectability and Discriminability of Elements of the Built Environment

Various elements of the built environment provide contrasts that pedestrians with vision disabilities may be able to use to guide themselves without the need for TDIs or other purpose-built wayfinding systems. Examples of potentially usable contrasts include (Dansk Blindesamfund 2015):

• Texture. Differences in texture between the surface of the pedestrian access route and what lies beyond its edges form boundaries that can be followed. For example, a grass strip bordering

• a paved walkway provides a recognizable difference in texture, but the difference in texture between brushed concrete and minimally textured pavers is not highly recognizable.
• Elevation. Continuous upward vertical elements adjacent to the walkway, such as building faces or low walls, can also form boundaries that can be followed; however, care should be taken not to block the adjacent space with street furniture or other obstacles. Downward vertical elements, such as street curbs, are less desirable for providing linear guidance, both because they may place the pedestrian in proximity to a potential hazard and because potential obstructions (e.g., lampposts, signs) are more likely to be found close to them.
• Projection. Railings installed along ramps, stairways, and bridges for other purposes also provide a physical feature people can follow.
• Color and luminance. Differences in color and luminance between the surface forming the pedestrian access route and the surface outside the route can provide an important supplement to other contrasting features for people with low vision. However, they are insufficient for people to be able to detect and discriminate between two surfaces underfoot or by using a long cane.
• Sound and resiliency. APTA’s tactile surface guidance (APTA 2020) and New York City DOT note that metal guidance strips tapped with a cane produce a detectably different sound from surrounding paving material. Contrasts in resiliency (i.e., how much a material gives when stepped on) can also be detectable underfoot or by how high a cane tip bounces when it touches the surface.

Evolution of Tactile Wayfinding

One of the first attempts to provide accessible wayfinding information was the installation of a system of TWSIs in Japan in the 1960s. Continuous pathways for persons with visual impairments were composed of raised bars running in the intended direction of travel combined with domes, truncated domes, or truncated cones to indicate locations requiring special attention. Those challenging locations included street crossings, high-level transit boarding platforms, and intersections and turns in the path. Figure 10 shows an example of a TWSI system in Japan connecting a train station entrance to bus stops, a pedestrian overpass to a business district, and the adjacent street network.

In subsequent decades, there has been some research to standardize TWSI geometry and various TWSI systems have been installed, usually comprising raised truncated domes and raised bars. However, the research is not comprehensive, and not all is applicable in the United States.

U.S. Research

The focus of much U.S. research has been on establishing DWSs, particularly for curb ramp and transit platform edge applications (Bentzen et al. 2021). ANSI Standard A117.1-1980 required “tactile warnings” at potentially hazardous areas in a building or site; specifically, at the tops of stairs, at reflecting pools, and at locations where there was no clear boundary between pedestrian and vehicular spaces. The warning could consist of exposed aggregate concrete, raised strips, or grooves. A variety of research efforts around the same time and later in the 1980s focused on identifying a highly detectable DWS (Aiello and Steinfeld 1979, Templer and Wineman 1980, Templer et al. 1982, Pavlos et al. 1985, Peck and Bentzen 1987). None of the ANSI A117.1-1980 surfaces were found to be highly detectable. Instead, the only highly detectable surfaces suitable for these applications were found to be truncated domes and raised rounded bars (Peck and Bentzen 1987).

Research in the 1990s confirmed the effectiveness of truncated domes. A 24-in.-wide (60 cm) DWS installed on transit platform edges resulted in decreased platform edge falls, both among persons who were visually impaired and overall (McGean 1991). Furthermore, installation of DWSs on curb ramps improved detection of the street by blind pedestrians (Hauger et al. 1996).

Scott et al. (2011) compared six tactile cues for aligning at a crossing: a curb ramp slope alone; a tactile arrow on an accessible pedestrian signal; a returned curb; two raised flat-topped bars, either parallel or perpendicular to the direction of travel; and a DWS where the last two rows of truncated domes were replaced by a single raised bar perpendicular to the direction of travel. The surfaces were constructed on plywood ramps and tested in an outdoor environment. The two surfaces producing the most accurate alignment contained raised bars perpendicular to the direction of travel.

Bentzen et al. (2017) installed a temporary raised-bar guidance surface at six noncorner crossings with the raised bars oriented perpendicular to the direction of travel across the crosswalk. Without the guidance surface, research participants passed the crosswalks without detecting them 18% of the time and aligned in a heading that would have resulted in completing the crossing outside the crosswalk 48% of the time. With the guidance surface, the crosswalk was missed 2.4% of the time and alignment that would have resulted in crossing completion outside the crosswalk was reduced to 23%.

Bentzen, Scott, and Myers (2020) tested four potential TWDs to separate sidewalk-level bicycle lanes from the pedestrian area: a 0.75-in.-high (19.1 mm) continuous raised trapezoid with bottom width 10.08 in. (25.6 cm) and top width 6.33 in. (16.1 cm); 12- and 24-in.-wide (30.5 and 61.0 cm) surfaces with relatively wide flat-topped bars 0.2 in. (5.1 mm) high; and 12- and 24-in.-wide (30.5 and 61.0 cm) “corduroy” surfaces of 0.2-in.-high (5.1 mm) narrower bars spaced closer together. A standard DWS was also included to provide baseline detectability and discriminability data. All surfaces were detected by participants with visual impairments more than 90% of the time, with no significant difference in detection rate. When contacting the various surfaces with their feet only (i.e., no cane), participants with visual impairments correctly identified the trapezoid 99% of the time, which was significantly better than for the flat-topped bars (87%), corduroy (72–81%, depending on approach angle), and DWS (76–83%, depending on approach angle). Participants with mobility impairment using a variety of aids had little difference in crossing each TWD surface compared to the DWS in terms of effort, instability, and discomfort.

International Standards and Practice

In 2008, the first international standard on dimensions for TWSIs was produced in Europe. This standard included six types of raised bar surfaces, two dome surfaces, two grooved surfaces, and one each of pyramidal, cylindrical, lozenge-shaped, and trapezoidal surfaces. The dimensions for each of these raised elements varied widely (European Committee for Standardization 2008).

By 2012, all countries that were part of the development of the ISO 23599 standard were already using some type of dome arrangement as a warning surface indicator. Where guidance paths were being installed, most countries used raised bars. Everywhere except the United States was using domes with raised bars as a TWSI system, where the domes served as attention fields not only for warning of hazards but also to indicate turns, intersecting paths, and key points of interest such as bus stops, elevators, tactile maps, or other waypoints. Canadian research in 2010 focused specifically on testing TDI paths combined with truncated domes to determine whether marking path intersections was useful for identifying where to make a turn in a route. They compared participants’ abilities to navigate turns in TDI paths configured into T-intersections, where the intersection decision point was either indicated with an area of truncated domes larger than the path width or not indicated. No effect was found in using the domes as a decision point indicator (Landry et al. 2010).

The ISO 23599 standard was published in 2012 after about 15 years of development work and was revised in 2019 with minor editorial changes. Due to the length of time needed to achieve consensus on the standard, the countries participating in its development had implemented different TWSI systems with varying technical specifications. As a result, the standard’s technical specifications for DWSs and TDIs allow for wide variation and the standard provides only general installation principles (Bentzen et al. 2021). Interestingly, the two countries much research on TWSIs comes from—Japan and the United Kingdom—do not officially have standards specifying how or where TWSIs are to be used in the public right-of-way. In fact, the United Kingdom has no standards for TWSIs, but its Guidance on the Use of Tactile Paving Surfaces (U.K. Department of the Environment, Transport and the Regions 1998; U.K. Department for Transport 2021) is generally followed as such.

Internationally, two different philosophies exist for the use of TWSIs. In Japan and other Asian countries, the philosophy is that TWSIs should provide continuous paths throughout the built environment (typically in the center of the sidewalk), even on pedestrian facilities bounded by buildings, landscaping, or curbs. In comparison, the philosophy in North America, most of Europe, Australia, and New Zealand is to install TWSIs only when the built environment provides insufficient guidance information (Bentzen et al. 2021).

Current U.S. Practice

Specifications

As noted, PROWAG (36 CFR Part 1190) specifies the dimensions for DWSs and where they are required to be used. DWSs are not to be set back from platform edges and curblines, as is more common internationally, and must be a minimum of 2 ft (610 mm) deep in the direction of travel. Currently, there are no U.S. specifications for the dimensions of TDIs or TWDs, nor are there national guidelines for their use.

The State of California (2019) provides standards for DWSs in its California Standards for Accessible Design Guide in Title 24, Part 2, Section 11B. These largely mirror PROWAG standards for dome dimensions and spacing. The California Building Code goes beyond the PROWAG specification for contrast of “light-on-dark or dark-on-light” (PROWAG R305.1.3) by specifying numerical

values of minimum visual contrast (11B-705.1.1.3). The California Building Code also requires the use of 36 in. of DWS in the direction of travel at perpendicular curb ramps (rather than 24 in. as specified in PROWAG) except where it is technically infeasible to provide a minimum turning space or in narrow cut-through medians (11B-705.1.2).

Existing Guidance

The FHWA’s Accessible Shared Streets guidance includes the section “Tactile Walking Surface Indicators and Detectable Edges,” which covers currently understood good practice for using TWSIs in shared-street environments in the United States (Elliot et al. 2017). Other industry guidance discusses the use of TWSIs generally, without guidance on specific tactile patterns or surfaces. For example, the National Association of City Transportation Officials’ Urban Street Design Guide (NACTO 2013) recommends using “tactile strips” along entrances to shared spaces; based on the footnote accompanying the guidance, the tactile strips would be DWSs. The American Society of Landscape Architects’ Universal Design guide (Dillon and Green 2019) contains recommendations for high-contrast “perpendicular tactile paving” to indicate hazards to those with no or low vision; an accompanying illustration shows DWSs at a crosswalk over a two-way separated bike lane and a roadway. Finally, APTA (2020) section 5.5.7 addresses “tactile paths” to aid pedestrians with vision disabilities in navigating between locations; “guide strips” (TDIs) are mentioned once. APTA’s guidance on tactile paths includes:

• Tactile paths should be continuous, with no interruption of guidance. If an interruption is unavoidable, the path should not change direction within this area unless the area is narrowly defined and the continuation of the path can be found reliably at the other end.
• Never change path directions within an intersection.
• Tactile paths should be distinct from DWSs and should be limited in use to avoid confusion with DWSs.
• Use consistent material, width, and color for the surface.
• Use consistent beginnings, endings, and decision points along the path.
• If implementing tactile paths, prioritize a path from bus stops and drop-off areas into the station, through the faregate (if used), and to the platform or stairway leading to the platform.

The APTA guidance also encourages the development of state or national standards for tactile paths and notes the user benefit of encountering consistent tactile path treatments when visiting different cities.

TWSIs in Public Right-of-Way Settings in the United States

This section and the next provide examples how U.S. transportation agencies have been applying TWSIs as of 2020. While these implementations were developed using the best information available to the agencies at the time they were developed, some of these examples are inconsistent with the latest guidance presented later in this report.

The Charlotte Department of Transportation (CDOT) installed TDIs as delineators to separate bicycle and pedestrian facilities, in addition to a handful of specific contexts: in a shared-use space, along the edge of a pedestrian-only path, and on bicycle ramps transitioning a bicyclist from the street to a shared-use path above street level. With regard to the latter, CDOT did not want pedestrians with vision disabilities to find a DWS and think it might be a crossing location.

The Seattle Department of Transportation (SDOT) adopted a similar approach to using TWSIs as delineators. SDOT installed 12-in.-wide (30.5 cm) TDIs between bike paths and pedestrian walkways and to alert pedestrians with vision disabilities to the existence of a shared street. At

time of writing, the agency was also piloting the use of a TDI on both sides of a crosswalk near a Lighthouse for the Blind, where there is heavy pedestrian and vehicle traffic on a busy arterial road. Seattle has also used modular curb with flexible posts as a delineator between pedestrians and bicyclists at sidewalk level Figure 11a).

San Francisco had explored the use of TWDs to separate sidewalks and adjacent bicycle facilities at the same grade (Figure 11b) and to separate pedestrian and bicycle zones on shared streets (Figure 11c).

The Florida Department of Transportation (FDOT) requires TDIs be installed in conjunction with bicycle ramps at roundabouts. As roundabouts are becoming more common in the state, particularly two-lane roundabouts, FDOT sees a need to allow bicyclists to travel on the sidewalk through the roundabout if they choose. To facilitate this movement, FDOT installs a bicycle ramp to provide access to a multiuse path on the sidewalk level. The TDIs are intended to guide pedestrians with vision disabilities away from the bicycle ramp so they correctly navigate from the multiuse path to the sidewalk beyond the bicycle ramp.

NYCDOT was also piloting the use of TWSIs around shared streets and bicycle lanes. Some bicycle lanes were delineated with a small drop in the curb, but in some cases where bicycle lanes are flush with the sidewalk, the city used a TDI.

TWSIs in Transit Settings

In the transit setting, TWSIs are used to guide passengers from the entrance of the station through the station via important points such as faregates and ticket kiosks, and ultimately to the platform. Sometimes the guidance surfaces lead down the platform and may intersect with TWSIs indicating boarding locations.

In the Seattle region, Sound Transit designs their 8-in.-wide (20.3 cm) raised-bar guidance path with the station entrance as the starting point, indicated by TDIs oriented perpendicular to the direction of travel across the open station entrance. TDIs oriented parallel to the direction

of travel then lead to ticket vending, ticket validation, a line map with information in braille, and vertical circulation elements (e.g., escalator, stairs, elevator; see Figure 12). The tactile wayfinding continues on the station mezzanine level, to the next vertical circulation element to the platform level and to raised bar guidance strips 6 ft (1.8 m) from the platform edges for guidance down the length of the platform. Intersections along the guidance strips lead to a central waiting and information area. Tile strips 6 ft (1.8 m) wide that have a minimally detectable sinusoidal surface extend across the width of the platform to indicate locations where train doors open. A minimum 4 ft (1.2 m) of circulation is provided on both sides of raised bar paths (Sound Transit 2021).

In the San Francisco Bay Area, Bay Area Rapid Transit (BART) stations were among the first in the United States to use DWSs along platform edges. As originally implemented, rectangles of raised-bar TDIs extended onto the platform from the DWS to indicate locations where train doors always opened. The introduction of new rail cars with three doors per side requires removal of the old door-opening indicators because the new door spacing is different. A quarter of all BART stations now have some raised bar TDIs (Figure 13). BART was also one of the first U.S. transit agencies to install raised-bar TDIs, but the program was put on hold in 2015.

In Los Angeles, LA Metro is in the process of installing raised-bar guidance surfaces in train stations and larger bus rapid transit facilities. Raised-bar surfaces guide people from entrances to stairs, tactile signage, telephones, ticket vending, faregates, and the platform. The agency uses 2-ft-square (0.6 m) truncated dome tiles as an attention field, and also places truncated domes at the tops and bottoms of stairs based on Japanese practice.

Washington Metropolitan Area Transit Authority (WMATA) places DWS strips 12 in. (30.5 cm) back from the platform edge, unlike any other U.S. rail property. As of 2020, WMATA was piloting raised-bar TDIs to indicate to people where they should wait to board an eight-car train. The agency was also piloting the use of a more extensive tactile wayfinding system in tandem with a Bluetooth navigation system. Early feedback from customers who use guide dogs led WMATA to consider using two double rows of tactile surfaces to improve detectability.

The Maryland Transit Administration uses larger areas of truncated domes at intersections of raised-bar guidance paths along with raised domes the same width as the guidance path as “waypoints” adjacent to tactile signage, landmarks, or other points of interest.

Guidance surfaces have been installed around floating bus islands in San Francisco and Seattle to guide people between the transit platform and the sidewalk, crossing the adjacent bicycle lane in the process. DWSs are used at each end of the crosswalks across the bicycle lane.