Highway signing for safety.

Shepard, Frank D · 1971 · ROSA P / Virginia Transportation Research Council

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Summary

This 1971 study by Frank D. Shepard investigates the effectiveness of temporary highway signing and traffic control devices in enhancing safety during maintenance operations on divided, limited-access highways. Motivated by the need to protect motorists and workers, the research aims to identify signing conditions that reduce accident potential by analyzing traffic flow characteristics. The study focuses on three specific maintenance scenarios: mowing, fixed shoulder work, and right lane closures. The experimental design involved field testing on a six-lane rural section of Interstate 95 near Ashland, Virginia, during the summer months of 1968–1970. Sixty-nine temporary signing conditions were evaluated using simulated maintenance activities, such as parked dump trucks and tractor mowers. Researchers manipulated several variables, including the presence of orange flags on signs, sign background colors (orange vs. yellow), lane closure taper devices (high-level warning devices, jumbo yellow cones, jumbo orange cones, and octopus devices), the number of sign indications (single vs. double sides), and the position of "LANE CLOSED" trailers or a new electronic sign panel. Data collection relied on manual observation of vehicle weaving maneuvers across five defined zones and radar spot speed checks at three points. Weaving maneuvers were weighted based on their proximity to the work area to assess the orderliness of traffic flow. The results indicated that flags on signs slightly increased weaving but improved attention-getting capabilities, leading to their inclusion in subsequent tests. Yellow sign backgrounds generally resulted in fewer weaves than orange backgrounds, though differences were often minimal. Regarding taper devices, orange cones proved superior to yellow cones and high-level warning devices; they induced earlier lane changes, reduced total weaving, and provided better delineation of the taper line. Yellow cones caused confusion and higher weaving rates near the work area. Double-sided sign indications were recommended for safety despite sometimes producing fewer weaves than single-sided signs, as they ensure visibility for all drivers. The electronic sign panel performed comparably to or better than the traditional "LANE CLOSED" trailer, particularly in encouraging early lane changes in Zone III, though it did not significantly alter speeds. The study concludes that specific signing configurations can significantly reduce accident potential by promoting orderly traffic flow. Key recommendations include using orange cones for lane closure tapers, employing double-sided signs, and utilizing electronic sign panels for enhanced visibility. The findings suggest that effective signing should command attention, convey clear meaning, and provide adequate time for driver response, thereby minimizing hazardous last-minute maneuvers near work zones.

Key finding

Yellow signs resulted in fewer weaving maneuvers than orange signs, orange cones provided better lane delineation and fewer weaves than yellow cones, and an electronic sign panel induced earlier and safer lane changes than a standard 'Lane Closed' trailer.

Methodology

field_study

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• signage environment
• work zones
• emergency work zone conspicuity
• perceptual countermeasures