00965568

Component

https://doi.org/10.3141/1844-08

http://scholar.google.com...kins&publication_year=2003

A study was conducted to determine the legibility impacts of freeway guide signs when encapsulated retroreflective sheeting is replaced with microprismatic retroreflective sheeting. The study included freeway guide signs mounted in an overhead position and exclusively illuminated with vehicle headlamps. A total of 60 subjects divided into three age groups participated in this nighttime study. All 60 subjects drove two vehicles, a modern sport utility vehicle (SUV) and a late-model passenger car. The findings show that microprismatic sheeting does provide statistically longer legibility distances than encapsulated sheeting. Overall, the improvement was 53 ft, or 9.5%. However, for the modern SUV, the improvement was much greater (78 ft) compared with the late-model passenger car (28 ft). The main differences are related to the evolution of vehicle design and specifications. Today's United States citizens prefer large vehicles such as an SUV, pickup, and minivan. These vehicles also meet recently revised headlamp specifications. These two issues inherently reduce the amount of headlamp light retroreflected from the sign back to the driver. Unfortunately, these counterproductive trends show signs of continuing. Considering the increasing proportion of older drivers in the United States, it becomes even more critical that transportation agencies do all they can to increase overhead-sign luminance. The findings show that increasing overhead-sign luminance by switching from encapsulated retroreflective sheeting to microprismatic retroreflective sheeting results in significantly longer legibility distances. The magnitude of the difference will continue to increase as long as the SUV-like proportion of the U.S. fleet continues to grow and headlamp specifications continue to direct less light toward overhead signs.

This paper appears in Transportation Research Record No. 1844, Traffic Control Devices, Visibility, and Rail-Highway Grade Crossings 2003.

English

p. 59-66

2003

Transportation Research Record

0309085799

Figures (7) ; Photos (4) ; References (6) ; Tables (3)

Age groups; Automobiles; Field tests; Guide signs; Headlamps; Legibility; Luminance; Night; Overhead traffic signs; Retroreflectivity; Sign sheeting; Specifications; Sport utility vehicles; Visibility distance

Encapsulated sheeting; Microprismatic sheeting

Geotechnology; Highways; Materials; Operations and Traffic Management; Society; I35: Miscellaneous Materials; I73: Traffic Control

TRIS, TRB, ATRI

Nov 18 2003 12:00AM

• DANCING DIAMONDS IN HIGHWAY WORK ZONES: EVALUATION OF ARROW-PANEL CAUTION DISPLAYS
• DETECTION AND IDENTIFICATION OF LIGHT-EMITTING DIODE TRAFFIC SIGNALS BY PROTAN OBSERVERS
• DRIVER UNDERSTANDING OF PAVEMENT MARKING COLORS AND PATTERNS
• DRIVING SIMULATORS FOR EVALUATION OF NOVEL TRAFFIC-CONTROL DEVICES: PROTECTED-PERMISSIVE LEFT-TURN SIGNAL DISPLAY ANALYSIS
• EFFECT OF VARIABLE-MESSAGE SIGNS IN REDUCING RAILROAD CROSSING IMPACTS
• FORECASTING TRAIN TRAVEL TIMES AT AT-GRADE CROSSINGS
• IMPROVING DILEMMA-ZONE PROTECTION OF ADVANCE DETECTION WITH ADVANCE-WARNING FLASHERS
• NIGHTTIME EXPERT PANEL AND PHOTOMETRIC EVALUATIONS OF UNLIGHTED OVERHEAD GUIDE SIGNS (WITH DISCUSSION AND CLOSURE)
• REDUCTIONS IN TRAFFIC SIGN RETROREFLECTIVITY CAUSED BY FROST AND DEW
• RELATIVE LUMINANCE OF RETROREFLECTIVE RAISED PAVEMENT MARKERS AND PAVEMENT MARKING STRIPES ON SIMULATED RURAL TWO-LANE ROADS
• SUPPLEMENTAL PAVEMENT MARKINGS FOR IMPROVING SAFETY AT RAILROAD-HIGHWAY GRADE CROSSINGS