Highway and Transportation Research Council

Transcription

1 OF ROTATION ON THE NIGHTTIME BRIGHTNESS OF EFFECTS HIGHWAY SIGNS UTILIZING HIGH INTENSITY SHEETING OVERHEAD Ao Benson James Assistant Student Highway and Transportation Research Council Virginia Cooperative Organization Sponsored Jointly by the Virginia (A of Highways and Transportation and the Department of Virginia) University Virginia 1974 November by Charlottesville, VHTRC 75-R12

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3 an initial step in the establishment of guidelines for the use of As intensity sheeting on overhead signs, a pilot study was made to investigate high effect of rotation on the average nighttime brightness of signs utilizing this the Rotation angles were chosen on the theory that the brightness will be material study concluded that while the theory used was generally, The did not significantly improve the average night brightness on the special rotation SIrMMARY maximum when the entrance angle is minimum. overhead signs evaluated

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5 OF ROTATION ON THE NIGHTTIME BRIGHTNESS OF EFFECTS HIGHWAY SIGNS UTILIZING HIGH INTENSITY SHEETING OVERHEAD A. Benson James Assistant Student the present time, the Virginia Highway and Transportation Research At is engaged in a study of the feasibility of using high-intensity ( ncapsu- Council lens) sheeting on overhead highway signs.(1) The preliminary results of the lated scheduled for publication in December 1974, have indicated that for selected study, the use of high intensity sheeting may be recommended as a replacement situations the presently used enclosed lens material. for economic benefits of high intensity sheeting are significant. The The enclosed lens sheeting currently used requires external illumination, which standard the expense of the initial light installation and the ever rising costs of entails and maintenance It is hoped that encapsulated lens sheeting, which does not power exterior lighting, can be substituted for the enclosed lens material and thus need considerable financial savings for the state. provide having a curved approach was considerably lower than the brightness of signs ways sites having a straight approach. Many of the brightness readings became un- at of this phenomenon was that if high intensity sheeting was to be utilized fication overhead highway signs in the state of Virginia, guidelines would have to be on formulated for that use the problem was not merely one of determining if the road However, affects the brightness of overhead highway signs using high intensity geometry this has been the subject of at least sheeting, previous study. (2) Also in- one was an examination of possible means of minimizing or even eliminating the volved so that the range of situations under which the proposed material might be effect, could be maximized utilized by INTRODUCTION AND PROBLEM the early data collection phases of the high intensity sheeting During project, it was observed that the brightness of signs located on road- evaluation low as the distance from the sign increased. This lack of uniformity acceptably that the approach was responsible for this effect. The immediate rami- suggested

6 objective of this study was to investigate the effect of rotation The the nighttime brightness of overhead highway signs utilizing high intensity on and to make observations Concerning the possible use of this technique sheeting the state highways. on to manpower, financial, and time constraints, the scope of this Due was limited to one study site project site selected for study was the overhead sign located on the exit The leading from the westbound lanes of Interstate Route 66 to Route 123 in ramp County as shown in Figure i This site was selected because the three- Fa±rfax curve was considered a desirable maximum degree of curvature for.arterial degree exit ramp selected for study is a two-lane facility containing The three-degree horizontal right curve and grade of 1o80%. The maximum safe speed a on this road is 45 miles per hour ( m/s). There is a limited visi- limit distance, approximately 900 feet ( m), due to geometry and topography bility this study the technique of sign rotation was examined for the In of seeking the maximum brightness of non-illuminated overhead signs on purpose containing approaches with horizontal curves In determining a method of roads rotation, the range of possible entrance angles (incidence angles) en- sign by a motorist approaching one of these signs was minimized. In general, countered entrance angle, as illustrated in Figure 2, is defined as that angle formed the a light ray striking a surface at some point and a line perpendicular to the by at the same point (4) For the pur poses of this report, the entrance surface was considered that angle subtended by the centerline of an approaching angle a point at the geometric center of the sign, and a line perpendicular to car, first step in the data collection phase was the taking of luminance The at the selected site. The before data, taken in conjunction with the readings high intensity evaluation study, were taken of the non-illuminated aforementioned intensity sign at several distances and from both the left and right lanes. high readings were taken with a Gamma Scientific, Inco Model 2009 Auto- All and recorded in foot-lambert units This particular nstru ent Telephotometer a range of 10-5 to 106 foot-lamberts (3.426 x 10-5 to x i0 cd/m ) and has photometric measurement accuracy is within 4% of full-scaleo the OBJECTIVE AND SCOPE STUDY SITE and interstate roads according to Virginia's Road Designs and s. (3) STUDY PROCEDURE the sign at that point.

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8 iaerpendicular to R::Ir :ct i: e second phase of the data collection consisted of mounting a The sign covered with the high intensity material The sign shown in Figure 3 special dimensions of 30" x 30" (o762 m x 762 m) and was divided into four squares, had silver and two green. This color scheme represen :ed both the background and two Incomin reflective surface Figure 2. Entrance angle.- legend materials found on overhead guide signs in Virginia Figure 3 Special high :intensity sign

9 sign was mounted near the center of the existing overhead sign in The to closely approximate a realistic height and entrance angle. order the left and right lanes, and with the car's headlights on both high and low both These readings were [.aken to obtain control, data. beams final phase ol data collection was the taking of readings from the The special sign at angles of 6, 9, andl2 degrees. (5) These angles placed the sign same with the line of sight at distances of 500, 600, and 700 feet perpendicular , and m), respectively, which encompassed the range of maxi- (152.40, brightness for encapsula ted lens materials (see Figure 4) The test vehicle mum a 1970 Plymouth Fury. was data were compiled and prepared for both numerical and graphical All All statistical parameters, were computed on a 95% confidence level. presentation. analysis was based on readings taken at the test site during two The over a one-month period The brightness was measured on the background and nights materials of the signs and from more than one location on the sign in order legend find a representation of the average brightness A total of 120 readings were to four the before conditions and 576 readings fqr the after conditions The recorded and after data and results of preliminary calculations appear in the Appendix before before and after data were compared for all corresponding parameters. The comparisons, shown in the Appendix, relate the averages, standard deviations, These In only one set of readings did a significant difference appear and brightness difference was not consistent at different distances from the sign. However, this 5-8 show that generally the brightness values were maximum a observation Figures facing the sign after it had been rotated, While this effect was not al- points The rotation of the specially iadricated sign made no statistically signiflc.an io in the average nighttime brightness difference were taken with no rotation at distances of 300, 450, 600, and 900 feet (91.44, , , , and m) from the sign, in 750, DATA ANALYSIS analysis techniques were employed whenever possible to minimize the possi- Computer of errors in calculation bility t values, and statistical significance of the Appendix leads to the conclusion that rotation of Inspection special sign made no statistically significant difference in the nighttime the unexpected, it is encouraging, sin.'e there might exist some road geometry together which this principle might be used in SUMMARY OF FINDINGS The findings of this s udy may be summarized as follows:

10 rotated Non sign Observation point Figure 4. Horizontal (3 o) curve Observation point AFTER BEFORE Rotated sign / / I Rotation scheme efore and after conditions. -6-

11 .] ii II!1 ("q'& I) 9ou u!mnq b -7-

12 o r LQ o "-i ",L,q) om3u!u, nq -8-

13 hd ("'-I " L ) OOU U.TCun I / / / / / -9-

14 ',,,, i &d) ooueu!tun I -10-

15 The findings of past studies were supported by the indication that when the 2 angle is at a minimum, the brightness will be at a maximum entrance was concluded that while the actual average brightness of the It sign did increase in many cases, there special no statistically signifi,ant was is recommended that further study be made on possible schemes which It improve the brightness of overhead signs utilizing high intensity sheeting would order that this material may be used in as many situations in possible and thus as the potential savings from its increase use CONCLUSIONS AND RECOMMENDATIONS improvement on a 95% confidence level

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17 Straub, Arthur L., and Terrence Mo Allen, "Sign Brightness in Relation 2. Distance and Reflectorization", HighwaY Research Record No 146, Position, Road Designs and s, Location and Design Division, Virginia Department 3. Highways, Richmond, Virginia, of Introduction to Reflective Materials, Traffic Control Products Division, 4o Mining and Manufacturing Company. Minnesota Youngblood, W. P 5. and H. L Woltman, "A Brightness Inventory of Contemporary o, Materials for Guide, Signs", Highway_.. Research Record Noo 377, Highway Signing REFERENCES R No, "Evaluation of High Intensity Sheeting for Overhead Highway Robertson, Virginia Highway and TranspQ ation Research Council, Charlottesville, Signs", Virginia (to be published) Highway Research Board, Washington, D.C., Research Board, Washington, D C,

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19 OF NIGHTTIME LUMI TANCE DATA IN FOOTLAMBERTS SUMMARY STATISTICAL SIGNIfiCANCE AND HEADLIGHTS OBJECTIVE: No. of Avg. Dist. (ft.) No. of Dist. (ft.) Conversion Units Basic Foot.3048 i tandard S APPENDIX HIGH BEAM BACKGROUND NO ROTATION ROTATION: SIX DEGREES Signifi- t Avg. cance value No No No No No i Footlambert cd/m

20 HIGH BEAM HEADLIGHTS" BACKGROUND OBJECTIVE" t V alue t Value o1315 o No Conversion Units Basic Fto o3048 m i APPENDIX CONTINUED ROTATION" NINE DEGREES Dist (ft.) No of Significance Avg o0014 o0611 No o No o No o No No ROTATION" TWELVE DEGREES NOo of Dist. (fto) Significance Avgo o4014 No o1609 No o1497 o No No 2 cd/m i Ft L 3o426

21 No. of Dist. (Ft.) HIGH BEAM HEADLIGHTS" LEGEND OBJECTIVE" t Value No No No No No Conversion Units Basic Ft m i APPENDIX CONTINUED NO ROTATION Avg I i OO ROTATION" SIX DEGREES No. of Dist. (Ft.) Significance Avg. i Ft.L cd/m

22 No. of Dist. (Fto) Conversion Units Basic Fto 3048 m i HIGH BEAM HEADLIGHTS" LEGEND OBJECTIVE: t Value Value APPENDIX CONTINUED ROTATION: NINE DEGREES No. of Dist. (Ft.) Significance Avgo No i, No No No No ROTATION: TWELVE DEGREES Avgo Significance o2908 No o No o No o6147 o1250,46955 No No i Ft.L cd/m

23 No. of Dist. (Ft.) No. of Dist. (Ft.) LOW BEAM HEADLIGHTS" BACKGROUND OBJECTIVE" t Value No Conversion Units Basic Ft m i APPENDIX CONTINUED NO ROTATION Avg ROTATION" SIX DEGREES Significance Avg i. 399 No No No o445 No i Ft.L cd/m

24 Conversion Units Basic Ft. =.3048 m i LOW BEAM HEADLIGHTS: BACKGROUND OBJECTIVE: t Value t Value APPENDIX CONTINUED ROTATION: NINE DEGREES No. of Disto (Ft,) Significance Avg Yes No o698 No No No ROTATION: TWELVE DEGREES No of Disto (Ft.) Significance Avgo o7718 No No No o126 No o No i Ft.L = 3,426 cd/m

25 LOW BEAM HEADLIGHTS" LEGEND OBJECTIVE" t Value No 'i. 973 No No No t Value No o9198 No io 705 No No o No Conversion Units Basic Ft m I APPENDIX CONTINUED ROTATION" NINE DEGREES No. of Dist. (Ft.) Significance Avg No ROTATION- TWELVE DEGREES No. of Dist. (Ft.) Significance Avg. i Ft.L cd/m

26 No. of Dist. (Ft.) LOW BEAM HEADLIGHTS" LEGEND OBJECTIVE" t Value No No Conversion Units Basic Ft m i APPENDIX CONTINUED NO ROTATION Avg ROTATION" SIX DEGREES t. No. o f Dis (Ft.) S ignificance Avg No No o No i Ft L cd/m