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Introduction > Recommendations > Rationale and Supporting Evidence > Glossary > References > Home
Highway construction and maintenance zones deserve special consideration with respect to older 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 accident analyses consistently show that more accidents 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 describing 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) believes 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 (NTSB, 1992). It is within this context that functional deficits associated with normal aging, as described below, may place older drivers at greater risk when negotiating work zones.
In an accident 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). Older drivers are most likely to demonstrate these deficits. Research on selective attention has documented that older adults respond much more slowly to stimuli that are unexpected (Hoyer and Familant, 1987), suggesting that older adults could be particularly disadvantaged by changes in roadway geometry and operations characteristic of construction zones. There is also research indicating that older adults are more likely to respond to new traffic patterns in an "automatized" fashion, resulting in more frequent driver errors (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 (1976) analysis relating simple, choice, and complex reaction time to crash involvement, only an increase in complex reaction time was associated with accidents. The relationship with driver age was most striking: the correlation between complex reaction time and accident involvement increased from 0.27 for the total analysis sample (all ages) to 0.52 when only older adults were included. Such data suggest that in situations where there is increased complexity in the information to be processed by drivers—such as work zones—the most relevant information must be communicated in a dramatic manner to ensure that it receives a high priority by older individuals.
Compounding their exaggerated difficulties in allocating attention to the most relevant aspects of novel driving situations, diminished visual capabilities among older 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, understand, make a decision, and complete a vehicle maneuver before reaching a sign—is increased significantly for older 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 decisionmaking.
This section will provide recommendations to enhance the performance of diminished-capacity drivers as they approach and travel through construction/work zones, keyed to five specific design elements: A. advance signing for lane closure(s); B. variable (changeable) message signing practices; C. channelization practices; D. delineation of crossovers/alternate travel paths; and E. temporary pavement markings.
The Handbook recommendations that follow are supported by material presented later in the "Rationale and Supporting Evidence" section under the "Construction/Work Zones" heading.
A. Design Element: Advance Signing for Lane Closure(s)
Redundant static signing should be used, where both the first upstream sign (e.g., W20-1) and the second sign (e.g., W20-5) encountered by the driver are equipped with flashing warning lights throughout the entire period of the lane closure, and a minimum letter height of 200 mm (8 in) is used.
The rationale and supporting evidence for this recommendation can be found by clicking here
B.Design Element: Variable (Changeable) Message Signing Practices
ROADWORK | NEXT | 2 MILES
while phase 2 could read:
LEFT | LANE | CLOSED
If legibility distance restrictions rule out a two-phase
display, the use of abbreviations plus elimination of the
problem statement is the recommended strategy to allow for
the presentation of the entire message on one phase:
LFT LANE | CLOSED | NEXT 2 MI
Where abbreviations are necessary in VMS operations, an adherence to the "acceptable," "not acceptable," and "acceptable with prompt" categories published by Dudek, Huchingson, Williams, and Koppa (1981) and reproduced in the "Rationale and Supporting Evidence" text for this section is recommended.
The rationale and supporting evidence for this recommendation can be found by clicking here.
C. Design Element: Channelization Practices
(1a) Traffic cones—900 mm (36 in) height (with at least a 300-mm [12-in] reflective collar for nighttime operations).
(1b) Traffic tubes—1,050 mm (42 in) height (with at least a 300-mm [12-in] reflective band for nighttime operations).
(1c) Vertical panels—300 mm (12 in) width.
(1d) Barricades—300 mm x 900 mm (12 in x 36 in) minimum dimension.
The rationale and supporting evidence for this recommendation can be found by clicking here.
The rationale and supporting evidence for this recommendation can be found by clicking here.
E. Design Element: Temporary Pavement Markings
or, if deemed a more cost-effective alternative:
It is recommended that temporary pavement markings shorter than 3 m (10 ft) be supplemented with devices including cones, tubes, or barrels placed on the centerline between opposing lanes, spaced (in feet) and maintained at not more than the construction zone speed limit (in miles per hour) apart.
The rationale and supporting evidence for this recommendation can be found by clicking here.
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