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Handbook for Designing Roadways for the Aging Population

Chapter 5. Construction/Work Zones

This section of the Handbook provides treatments to enhance the performance of aging drivers as they approach and travel through construction/work zones, keyed to five specific design elements. Also, after the last element, two promising practices treatments are provided. Drawings are for illustrative purposes only; they are not to scale and should not be used for design purposes.

Proven Practices

  1. Signing and Advance Warning
  2. Portable Changeable (Variable) Message Signs
  3. Channelization (Path Guidance)
  4. Delineation of Crossovers/Alternate Travel Paths
  5. Temporary Pavement Markings

Promising Practices

  1. Increased Letter Height for Temporary Work Zone Signs
  2. Work Zone Road Safety Audit (WZRSA)

Highway construction and maintenance zones deserve special consideration with respect to aging driver needs because of their strong potential to violate driver expectancy. Alexander and Lunenfeld (1986) properly emphasized that driver expectancy is a key factor affecting the safety and efficiency of all aspects of the driving task. Consequently, it is understandable that crash analyses consistently show that more crashes occur on highway segments containing construction zones than on the same highway segments before the zones were implemented (Juergens, 1972; Graham, Paulsen, and Glennon, 1977; Lisle, 1978; Nemeth and Migletz, 1978; Paulsen, Harwood, and Glennon, 1978; Garber and Woo, 1990; Hawkins, Kacir, and Ogden, 1992).

Work-zone traffic control must provide adequate notice to motorists that describes the condition ahead, the location, and the required driver response. Once drivers reach a work zone, pavement markings, signing, and channelization must be conspicuous and unambiguous in providing guidance through the area. The National Transportation Safety Board (NTSB, 1992) stated that the MUTCD guidelines concerning signing and other work-zone safety features provide more than adequate warning for a vigilant driver, but may be inadequate for an inattentive or otherwise impaired driver. It is within this context that functional deficits associated with normal aging, as described below, may place aging drivers at greater risk when negotiating work zones.

In a crash analysis at 20 case-study work-zone locations, among the most frequently listed contributing factors were driver attention errors and failure to yield the right-of-way (Pigman and Agent, 1990). Aging drivers are most likely to demonstrate these deficits. Research on selective attention has documented that aging adults respond much more slowly to stimuli that are unexpected (Hoyer and Familant, 1987), suggesting that aging adults could be particularly disadvantaged by changes in roadway geometry and operations such as those found in construction zones. There is also research indicating that aging adults are more likely to respond to new traffic patterns in an "automatized" fashion, resulting in more frequent driver error (Fisk, McGee, and Giambra, 1988). To respond in situations that require decisions among multiple and/or unfamiliar alternatives, with unexpected path-following cues, drivers' actions are described by complex reaction times that are longer than reaction times in simple situations with expected cues. In Mihal and Barrett's analysis (1976) relating simple, choice, and complex reaction time to crash involvement, only an increase in complex reaction time was associated with crashes. The relationship with driver age was most striking: the correlation between complex reaction time and crash involvement increased from r = 0.27 for the total analysis sample (all ages) to r = 0.52 when only aging adults were included. Such data suggest that in situations where there is increased complexity in the information to be processed by drivers—such as in work zones—the most relevant information must be communicated in a dramatic manner to ensure that it receives a high priority by aging individuals.

Compounding their exaggerated difficulties in allocating attention to the most relevant aspects of novel driving situations, diminished visual capabilities among aging drivers are well documented (McFarland, Domey, Warren, and Ward, 1960; Weymouth, 1960; Richards, 1972; Pitts, 1982; Sekuler, Kline, and Dismukes, 1982; Owsley, Sekuler, and Siemsen, 1983; Wood and Troutbeck, 1994). Deficits in static and dynamic acuity and contrast sensitivity, particularly under low-luminance conditions, make it more difficult for them to detect and read traffic signs, to read variable message signs, and to detect pavement markings and downstream channelization devices. Olson (1988) determined that for a traffic sign to be noticed at night in a visually complex environment, its reflectivity must be increased by a factor of 10 to achieve the same level of conspicuity as in a low-complexity environment. Mace (1988) asserted that the minimum required visibility distance—the distance from a traffic sign required by drivers in order to detect the sign, understand the situation, make a decision, and complete a vehicle maneuver before reaching a sign—is increased significantly for aging drivers due to their poorer visual acuity and contrast sensitivity, coupled with inadequate sign luminance and legend size. Other age-related deficits cited by Mace (1988) include lowered driver alertness, slower detection time in complex roadway scenes due to distraction from irrelevant stimuli, increased time to understand unclear messages such as symbols, and slower decision making.

In a mail survey of 1,329 AARP members ages 50 to 97, conducted to identify aging driver freeway needs and capabilities, 21 percent of the respondents indicated that they have problems with accurately judging distances in construction zones (Knoblauch, Nitzburg, and Seifert, 1997). These drivers reported additional problems in negotiating work zones, including congestion/traffic; lack of adequate warning; narrow lanes; lane closures and lane shifts; and difficulty staying in their lane.

Proven Practices
43. Signing and Advance Warnings

A. Flashing Yellow Arrow Panel

At construction/maintenance work zones on high-speed roadways (where the posted speed limit is 45 mph or greater) and divided highways, the consistent use of a flashing arrow panel located at the taper for each lane closure is recommended as shown in Figure 61.

References *: MUTCD:4

Figure 61. An image of a work zone lane closure that shows the placement of a flashing arrow panel where the closure taper begins in the travel lane.

Figure 61. Flashing arrow panel at lane closure taper

B. Lane Closure Advance Signing

In implementing advance signing for lane closures as per MUTCD Part 6, it is recommended that:

References *: TEH:4, MUTCD:4

Figure 62. An image of a work zone lane closure that shows the placement of a changeable message sign upstream of the lane closure.  The dimension of 0.5 to 1.0 miles is specifically defined between the sign and the closure.  The message on the sign reads 'RIGHT LANE CLOSED'.

Figure 62. Changeable message sign upstream of lane closure taper

Figure 63. An image of a work zone lane closure on a two-lane two-way highway that shows the placement of static signs on both sides of the roadway upstream of the lane closure.  The image shows a 'ROAD WORK AHEAD' sign followed by a 'RIGHT LANE CLOSED XX FT' sign on both sides of the roadway for drivers approaching the closed lane.  Each sign has a yellow beacon above it.

Figure 63. Redundant static signs upstream of lane closure taper

C. Sign Sheeting

To increase the legibility distance of ground-mounted work-zone signs, the use of fluorescent orange is recommended over the use of beaded high-intensity orange sheeting.

References *: MUTCD:1, NCHRP 500-9:4

D. Legibility Distance

A minimum specific ratio of 1 inch of letter height per 30 feet of legibility distance should be used.

References *: TEH:4, MUTCD:1

The rationale and supporting evidence for these treatments can be found beginning on page 290 of this Handbook.

44. Portable Changeable (Variable) Message Signs

A. Number of Phases

The MUTCD requires that no more than two phases be used on a changeable message sign (CMS). If a message cannot be conveyed in two phases, multiple CMSs and/or a supplemental highway advisory radio message should be used; alternatively, the action statement only may be presented on a single page/phase.

References *: TEH:2, MUTCD:4

B. Display Time

Each phase of a CMS message should be displayed for a minimum of 3 s.

References *: MUTCD:1

C. Units of Information

D. Sign Content

When a CMS is used to display a message in two phases, the problem and location statements should be displayed during phase 1 and the effect or action statement during phase 2, as illustrated in Figure 64.

If legibility distance restrictions rule out a two-phase display, the use of abbreviations [as specified in the MUTCD (FHWA, 2007)] plus elimination of the problem statement is the recommended strategy to allow for the presentation of the entire message in one phase, as illustrated in Figure 65.

References *: TEH:4, MUTCD:4

Figure 64. An image of two phases of a message on a changeable message sign. The sign on top of the image has a message that reads 'ROAD WORK 2 MILES'. The sign on the bottom of the image reads 'LEFT LANE CLOSED'.

Figure 64. Phase 1 (Top) and Phase 2 (Bottom)

Figure 65. An image of a changeable message sign that reads 'LEFT LN CLOSED IN 2 MI'.

Figure 65. Use of approved abbreviation in one-phase message

E. Legibility

For superior legibility:

F. Sign Height

Portable changeable message signs should be elevated to a height sufficient to be seen across multiple lanes of (same-direction) traffic by approaching passenger car drivers.

References *: MUTCD:4

The rationale and supporting evidence for these treatments can be found beginning on page 300 of this Handbook.

45. Channelization (Path Guidance)

A. Device Dimensions

The following minimum dimensions or properties for channelizing devices used in highway work zones are recommended to accommodate the needs of aging drivers:

B. Device Spacing

Channelizing devices through work zones (in non-crossover applications) should be spaced at no more than a distance in feet equal to the speed limit through the work zone in miles per hour (e.g., in 40-mph work zone, channelizing devices should be spaced no farther apart than 40 ft). 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-mph zone, space the devices no farther apart than 20 ft).

References *: MUTCD:4

C. Reflectors

The use of side reflectors with cube-corner lenses or reflectors (facing the driver) mounted on top of concrete safety-shaped barriers and related temporary channelizing barriers is recommended, spaced (in feet) at no more than the construction zone speed limit (in miles per hour) through a work zone.

References *: MUTCD:4

The rationale and supporting evidence for these treatments can be found beginning on page 313 of this Handbook.

46. Delineation of Crossovers/Alternate Travel Paths

A. Positive Barriers

Use positive barriers in transition zones and positive separation (channelization) between opposing two-lane traffic throughout a crossover, for intermediate- and long-term-duration work zones, for all roadway classes except residential.

References *: MUTCD:1

B. Device Spacing

A maximum spacing (in feet) of one-half the construction zone speed limit (in miles per hour) for channelizing devices (other than concrete barriers) is recommended in transition areas, and through the length of the crossover, and in the termination area downstream (where operations as existed prior to the crossover resume).

References *: MUTCD:4

C. Reflectors

Use side reflectors with cube-corner lenses spaced (in feet) at no more than the construction zone speed limit (in miles per hour) on concrete channelizing barriers in crossovers (or alternately, the use of retroreflective sheeting on plastic glare-control louvers [paddles] placed in crossovers).

References *: MUTCD:4

D. Screens

It is recommended for construction/work zones on high-volume roadways that glare-control screens 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 in.

References *: MUTCD:4

The rationale and supporting evidence for these treatments can be found beginning on page 318 of this Handbook.

47. Temporary Pavement Markings

A. Raised Pavement Markers

Where temporary pavement markings shorter than the 10-ft standard length are implemented, it is recommended that a raised pavement marker be placed at the center of the gap between successive markings.

References *: MUTCD:2

The rationale and supporting evidence for this treatment can be found beginning on page 323 of this Handbook.

Promising Practices

These are treatments being utilized by transportation agencies that should benefit aging road users as determined by a subjective assessment by staff participating on the development of this Handbook. Current trends indicate these practices have a positive impact on aging road user safety.

48. Increased Letter Height for Temporary Work Zone Signs

It is recommended that some "action" words on temporary work zone signs on portable sign stands have a minimum letter height of 8 in. (see Figure 67)

References *: MUTCD:4

Figure 67. An image of an orange work zone sign with the message 'RIGHT LANE CLOSED AHEAD' in black letters.  The words 'RIGHT' and 'CLOSED' have a larger letter height than the other words.

Figure 67. Temporary work zone sign with increased letter height

The rationale and supporting evidence for these treatments can be found beginning on page 328 of this Handbook.

49. Work Zone Road Safety Audit (WZRSA)

The Work Zone Road Safety Audit Guidelines and Prompt Lists provide a process for individuals or agencies performing formal work zone safety examinations to improve the safety of workers and all roadway users, including the aging population. This document includes guidance on conducting Road Safety Audits (RSA) at all phases of work zone planning, design and deployment, and considerations for each project phase. The guidelines and prompt lists explain the importance of the Work Zone RSA and navigate the practitioner through the RSA process.

References *: MUTCD:4

The rationale and supporting evidence for these treatments can be found beginning on page 329 of this Handbook.

References Legend

See pages 3 and 4 for full description of codes and acronyms of cited design guides.

Page last modified on October 15, 2014.
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