Best Practices Guidelines for Sign Materials

Transcription

1 Best Practices Guidelines for Sign Materials 1.0 Introduction 1.1 These guidelines are for standard sign applications. For locations that are deemed hazardous a detailed assessment is required and may require materials that exceed minimum standards for function and classification of signs. 1.2 There are no written guidelines for the selection of sign materials and it is proposed to develop guidelines for the selection of sign materials based on wind loads, strength of support systems, and type of sign (i.e. Regulatory, Warning or Information). 1.3 All materials supplied shall be in accordance with the Alberta Transportation Products list. The type of sign supplied shall be either Standard or Non- Standard. Signs manufactured on 2.0mm flat tensioned-leveled aluminum backing are considered Standard Signs. Signs manufactured on 18.5mm (3/4 ) plywood or extruded aluminum are considered Non-Standard Signs. 1.4 The primary function of a small sign support system is to position a sign panel so that the message is communicated to the driving public. A secondary function or benefit of a sign support system is to give way or yield during vehicular impact so that occupants of the striking vehicle sustain, at most, minor injuries and the vehicle is not severely damaged. Safety would therefore be the primary consideration. A cost benefit analysis conducted to determine the most appropriate small sign support system for a given agency would consider both present and future costs associated with various sign support systems under consideration. Manufacturers of sign support systems have tables/charts for a variety of wind pressure conditions showing the allowable sign size and number of steel posts required. The manufacturers products must meet the FHWA Guidelines for Selecting a Cost Effective Small Highway Sign Support System. 2.0 Function and Classification of Signs 2.1 Function Traffic control devices constitute a system for conveying messages to the road user. It is the objective of these messages to advise of traffic regulations in order to enable observance of the law, warn of roadway characteristics and road hazards, and provide the information necessary for route selection. Meeting the objectives improves the safety and serves the convenience of the road user, and promotes the efficient movement of persons and goods, and the orderly flow of traffic. (Manual of Uniform traffic control devices for Canada). December 17, 2003 Page 1 of 13

2 2.2 Classification Regulatory Signs Regulatory Signs shall indicate a traffic regulation, which applies at a specific time or place upon a highway, disregard of such regulation constitutes a violation under the Highway Traffic Act. They are essential to indicate the applicability of legal requirements that may not otherwise be apparent. Due care must be exercised to ensure that they are erected wherever needed to fulfill this purpose and that unnecessary mandates are avoided. Regulatory Signs shall be erected at those locations where the regulations apply and shall be easily visible to the motorist. The message on the sign shall clearly indicate the requirements imposed by the regulation. Signs that have been erected but are no longer applicable shall be removed Warning Signs Warning Signs, when used shall indicate in advance, conditions upon or adjacent to a highway that are potentially dangerous to the road user. Such conditions will normally require caution on the part of the driver and may necessitate a reduction in speed. Adequate warning signs are therefore of real assistance to the road user in terms of safety and in expediting traffic flow. However, the overuse of warning signs may promote disrespect for traffic control devices and the use of such signs should be kept to a minimum. Improved highway design will generally have the effect of reducing the need for Warning Signs Information Signs The purpose of information signs is to convey information to the motorist for the selection of his/her route, for the location of off road facilities, or for the identification of special geographical features or points of interest. Information signs are presented in several sub-classes as follows: Class 1A Class 1B Class 1C Class 1D - Guide Signs - Route Marker Signs - Off Road Facilities Signs - Miscellaneous Information Signs 3.0 Effective Sign Management There are several important components to an effective management program. Established standards for signing that conform to laws as well as motorists visibility needs. December 17, 2003 Page 2 of 13

3 An inventory of all traffic control signs should be maintained and signs inspected regularly, both in daylight and at night. Highly hazardous areas should be surveyed, to make sure they are properly marked. A scheduled sign replacement program should be established, based on the performance life of the reflective sheeting that is used. 4.0 Applicable Documents 5.0 Standards Highway Geometric Design Guide (1999) Highway Standard Plates CB-6 Standards Alberta Highway Pavement Marking Guide (1999) Traffic Accommodation in Work Zones (1999) Traffic Control Standards (1995) (Chapter 2) Traffic Control Standards (1995) Excerpts Uniform Traffic Control Devices for Canada FHWA-1P-79-7, Guidelines for Selecting a Cost-Effective Small Highway Sign Support System - FHWA-IP-79-7 Guidelines for Selecting a Cost-Effective Small Sign Support System - AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals, AASHTO A Guide to Small Sign Support Hardware, National Cooperative Highway Research Program (NCHRP Report 350) - American Society for Testing of Materials, Standard Specification for Retroreflective Sheeting for Traffic Control (ASTM-D4956) 6.0 Reflective Sheeting 6.1 Purpose The purpose of reflective sheeting material is to provide night-time visibility of the sign messages to help drivers of all ages make safe driving decisions. In order to provide the required night-time luminiance, relfective sheeting must meet minimum retroreflectivity standards. December 17, 2003 Page 3 of 13

4 Retroreflection occurs when surfaces (sign) return a portion of the directed light to its source (driver). This is why retroreflective materials appear brightest to observers located near the light source (a driver and the vehicle headlights). 6.2 Types of Sheeting Materials Retroreflective sheeting shall be classified as follows (ASTM D4956): High Intensity Type III A High-Intensity retroreflective sheeting, typically composed of encapsulated glass-bead retroreflective material. Type IV A High-Intensity retroreflective sheeting. This sheeting is typically an unmetallized microprismatic retroreflective element material. 6.3 Reflective Sheeting General Requirements Permanent Highway Signs Alberta Transportation s minimum requirements are specified in the Alberta Transportation Products list, Standard Specifications for Highway Construction, Specification 5.18, (Supply of Permanent Signs, Posts and bases) section (Reflective Sheeting): Reflective Sheeting shall meet or exceed the minimum requirements as specified in ASTM-D4956, Performance Requirements Type III, High Intensity Retroreflective Sheeting. Overhead Sign Reflective Sheeting 3M Scotchlite, Diamond Grade VIP is recognized as very high brightness retroreflective prismatic sheeting for overhead signs without illumination. The Stimsonite Series 6200 High-Performance and 3M Scotchlite, Diamond Grade LDP are being evaluated ( ) prior to establishing a minimum standard. Temporary Orange Work Zone/Construction Signs (Specification 7.1) All signs, barricades and other traffic control devices shall conform to the requirements for shape, colour and size specified in Section IV of the Department manual entitled Traffic Accommodation in Work Zones. The orange portion of all signs, barricades and other traffic control devices shall be fully reflectorized using High Brightness, Retroreflective, Non-Metallized, Prismatic Sheeting Material which incorporates durable, transparent fluorescent pigment and meets the following requirements December 17, 2003 Page 4 of 13

5 BRIGHTNESS REQUIEMENTS (90 0 Rotation Angle) Observation Angle Entrance Angle Orange A Minimum Coefficient of Retroreflection (R A ) cd/fc/ft 2 (cd. lx -1. m -2 ) 7.0 Substrate Materials (backing) 7.1 Purpose The substrate material can be of wood or aluminum. The reflective sheeting material has to be compatible with the substrate material to give a strong bond. Substrate materials must be of sufficient strength to resist tearing at connections (i.e. bolts) from wind loads. 7.2 Substrate Materials General Requirements Alberta Transportation s minimum requirements for substrate materials are specified in the Alberta Transportation Products list and Standard Specifications for Highway Construction, Specification 5.18, (Supply of Permanent Signs, Posts and Bases) section (Backing): Aluminum: Tensioned Leveled Aluminum for Standard Signs Tensioned leveling is a technique that gives aluminum sheets a superior flatness and resistantance to tearing at connections. The aluminum sheet is also recyclable. - Aluminum shall be a minimum of 2 mm flat sheet tension leveled, sign grade aluminum (6061-T6 or 5052-H38). NOTE: Experience indicates that tensioned leveled aluminum standard signs do not perform in locations of high wind gusts, ¾ plywood may be substituted. Extruded Aluminum for Major Signs (Non-Standard Signs) Extruded aluminum highway sign panels have excellent resistance to corrosion, are lightweight and strong. The aluminum sign panels are also recyclable. - Extruded aluminum (6061-T6 or 6063-T5) panels (Alcan Shape # 73247) (drawing TEB 1.95) shall be used for major signs. December 17, 2003 Page 5 of 13

6 Plywood: High Density Plywood is an engineered wood that is versatile, economical and environmentally friendly. Its special feature is the superior machineability that delivers flawless edges, intricate profiles and components cut to exacting precision. The surface is flat, smooth, dense and free of knots and grain patterns. High Density overlaid plywood is suitable for both exterior and interior signs including those where reflective tape is to be applied directly to the surface. The resin overlay needs no surface preparation and the tape will adhere firmly to it. Thicknesses used are as follows: Hi-Density (3/4 ) 18.5 mm Plywood for Permanent Signs (Non-Standard Signs) 8.0 Ancillary Materials: (3/4 ) 18.5 mm (100/100 or 120/120 Hi-Density) plywood is used for permanent signs larger than 90 cm X 90 cm. Wind frames shall be used for signs that are over 2.97m 2 (32 ft 2 ) in area (for illustration see drawings TEB 1.72 and TEB 1.75). Girds (Girts) (structural members) are used for stiffening plywood sign panels where panels join together or require stiffening e.g. information signs that are long and narrow. The structural members (girds) are mounted as shown on drawings TEB 1.72 and TEB All nuts, washers and bolts to be corrosion resistant. 9.0 Support Systems for Small Highway Signs Systems currently used by Alberta Transportation: - Wooden posts (10 cm x 10 cm, 10 cm x 15 cm & 15 cm x 20 cm) - Breakaway steel sign supports (I-beam posts for larger signs) Recognized Sign Support Systems (Single Post): - Steel U-Post or Flanged Channel - Wood Post - Steel Pipe (schedule 40) - Square Steel Tube - Aluminum Type X Post (magnode system) December 17, 2003 Page 6 of 13

7 These support systems are included in the FHWA-IP-79-7 guidelines for selecting a Cost Effective Small Highway Sign Support System. The systems have been evaluated in terms of current safety performance criteria ( Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals, American Association of State Highway and Transportation Officials, 1994) and found to be satisfactory for single post installations. The report evaluated all commonly used sign supports on the basis of initial costs, and costs of components, installation, collision repair, salvage value and normal maintenance. Support Systems Evaluated: A total of seven support systems were evaluated (FHWA-IP-79-7, Guidelines for Selecting a Cost-Effective Small Highway Sign Support System) as per the following: December 17, 2003 Page 7 of 13

8 Required Sizes Minimum Size of Support Elements For Panel Area of: System 0.65m m 2 1. Full length steel flanged channel or U-post, galvanized 4.47 kg/m Two 2.98 kg/m posts 2. Steel flanged channel or U-post base and signpost with bolted base assembly, galvanized (Eze- Erect System) 4.47 kg/m post and 4.47 kg/m base Two 2.98 kg/m posts and Two 4.10 kg/m bases 3. Southern pine, grade 2, treated wood post 4. Standard steel pipe, schedule 40, galvanized 5. Standard steel pipe, schedule 40, with triangular slip base, galvanized 10 cm x 15 cm (normal) 10 cm x 15 cm (normal) 5.1 cm I.D. 6.4 cm I.D. (with threaded pipe collar) 5.1 cm I.D. 6.4 cm I.D. 6. Telescoping square steel tube (Telspar System), galvanized 7. Aluminum type X (Magnode Product, In., System) 5.7 cm x 5.7 cm x 2.67 mm post 6.4 cm x 6.4 cm x 2.67 mm anchor and 7.6 cm x 7.6 cm x 3.43 mm sleeve Two 2X posts 6.4 cm x 6.4 cm x 3.43 mm post and 7.6 cm x 7.6 cm x 4.76 mm anchor Two 3X posts Yield stresses (F Y ) used in this evaluation are as follows: Post Type Yield (F Y ) (MPa) Steel flanged channel or U-post Wood 9.3 Standard steel pipe Square steel tube Aluminum type X December 17, 2003 Page 8 of 13

9 SYSTEM Embedment Details Base length (cm) ASSUMED EMBEDMENT DETAILS Embedment Depth Method of Embedment (cm) 1. (a) 4.47 kg/m full-length steel U-post None 107 cm Driven (b) Two 2.98 kg/m full-length steel U-posts None 107 cm Driven 2. (a) 4.47 kg/m steel U-post base and signpost with bolted base assembly (b) Two 4.09 kg/m steel U-post bases and two 2.98 kg/m steel U-signposts with bolted base assemblies 107 cm 94 cm Driven 107 cm 94 cm Driven cm x 15 cm wood post None 122 cm Drill and Backfill 4. (a) 5.1 cm I.D. steel pipe None 107 cm (i) Drill and Backfill (b) 64 cm I.D. steel pipe with threaded pipe collar 61 cm 76 cm concrete footing 61 cm base 30 cm O.D. non reinforced concrete footing 5. Steel pipe with triangular slip base 71 cm 76 cm concrete footing 61 cm base 30 cm O.D. non reinforced concrete footing 6. Telescoping square steel tube 107 cm base 46 cm sleeve 102 cm base 40 cm sleeve Driven 7. (a) Two full-length aluminum type 2X posts None 107 cm Driven (b) Two full-length aluminum type 3X posts None 107 cm Driven (i) It is assumed that a 10 cm x 30 cm x 6.35 mm steel plate is welded to the base of the post to prevent twisting from wind loads December 17, 2003 Page 9 of 13

10 Crashworthy Single-Post Sign Support Systems SIZE LIMITS SYSTEM DESCRIPTION DESIRABLE MAXIMUM A. Steel U-post or flanged channel a. Rail steel U-post with bolted base assembly (Eze-Erect System) 5.96 kg/m (i) - b. Full-length rail steel U-post 4.47 kg/m (ii) 8.93 kg/m (iii) (iii) (iv) c. Full-length experimental billet steel U-post 8.93 kg/m d. Vertical U-post with U-post back brace kg/m e. Full length billet steel U-post kg/m B. a. Wood post (with no breakaway or weakening devices) (treated wood post) b. Wood post (treated wood post) with drilled holes to effect breakaway during impact - post embedded in concrete footing 10 cm x 15 cm (v) (nominal size) 10 cm x 20 cm (v) (nominal size) C. Steel pipe (Schedule 40) a. Full-length pipe with no breakaway or weakening devices 5.1 cm diameter 5.1 cm diameter b. Pipe with breakaway collar 10 cm diameter 6.4 cm diameter c. Pipe with breakaway slip base 10 cm diameter (iv) D. Square steel tube (perforated) with breakaway base (Telspar System) 6.4 cm x 6.4 cm 3.5 mm thick E. Aluminum Type X post (Magnode System) 3X (vi) 6X (vi) (iv) (iv) (iv) (i) (ii) (iii) (iv) (v) (vi) System not available for post larger than 5.96 kg/m. However, tests of a multiple post installation in which three 5.96 kg/m posts were impacted simultaneously proved satisfactory, i.e., change in momentum was less than desirable limit. Tests of post sizes between 4.47 kg/m and 8.93 kg/m have not been conducted, hence the desirable size limit is not known. Two 4.47 kg/m posts bolted together back-to-back. Maximum size limit unknown. Tests of larger sizes not available, hence desirable limit is unknown. Size designations are Magnode Products, Inc., designation. Post sizes between 3X and 6X have not been tested, hence the actual desirable limit is unknown. December 17, 2003 Page 10 of 13

11 Sign Support Evaluation Procedure: - Select candidate support system Evaluate impact performance characteristics Does system satisfy current safety and design standards, AASHTO/FHWA, prime considerations should be given to systems that offer the least hazard to motorists? Systems design characteristics Does system satisfy design specifications of Agency and/or AASHTO (loads, allowable stresses, esthetics and functional requirements are all addressed in the specification) Does system have acceptable methods of embedment (most posts are driven into the ground by sledgehammer or powered equipment. Wood posts are commonly placed in a drilled or excavated hole) Conduct Economic Analysis Rank System Select System Other factors to consider are availability, durability, aesthetics, torsion, and sign flutter. Sign posts (supports), foundations and mountings shall be so constructed as to hold signs in a proper and permanent position and to resist swaying in the wind or displacement by vandalism. All sign supports within the clear zone must either be of a breakaway type meeting the crashworthiness criteria set in NCHRP Report 350 or be protected by guardrail, barrier, or an energy absorbing system meeting NCHRP Report 350 criteria. In any case, use of a support system, which does not satisfy the safety performance standards of the specifications, should be avoided unless it is shielded by an existing traffic barrier. Selection of Sign Support Systems: Small Sign Support Systems (Posts) are designed to withstand a variety of wind pressure (wind load) conditions meeting FHWA guidelines for small sign support systems and AASHTO specification for structural supports for highway signs. December 17, 2003 Page 11 of 13

12 Manufacturers have designed their small sign support systems to FHWA and AASHTO requirements. All manufacturers have wind load tables/charts that give the support size (post), height of sign above ground, and maximum area of sign it can support. The tables/charts are based on wind velocity of (70mph) km/hr. The manufacturers tables/charts are easy to use and assist in the selection of the size of support system required supporting a specified size of sign. The following chart is a sample of a proprietary sign support system (Ulti-Mate Sign Support System): SINGLE POSTS WIND VELOCITY 112 Km/Hr (70 MPH) 2.8 mm thick (12 GA.) PERFORATED SQUARE POSTS Fy = 414Mpa (60,000 PSI) Post Size Ht. Bottom of Sign Area of Sign Maximum 38 mm 1.5 m 0.50 m 2 38 mm 1.8 m 0.43 m 2 38 mm 2.1 m 0.37 m 2 38 mm 2.4 m 0.31 m 2 45 mm 1.5 m 0.81 m 2 45 mm 1.8 m 0.68 m 2 45 mm 2.1 m 0.58 m 2 45 mm 2.4 m 0.47 m 2 45 mm 2.7 m 0.41 m 2 50 mm 1.5 m 1.14 m 2 50 mm 1.8 m 0.95 m 2 50 mm 2.1 m 0.84 m 2 50 mm 2.4 m 0.70 m 2 50 mm 2.7 m 0.58 m 2 50 mm 3.05 m 0.50 m 2 December 17, 2003 Page 12 of 13

13 10.0 Selection of Large Sized Sign Support System: For the selection of a sign support system for larger sized signs refer to the Traffic Control Standards Manual, drawing number TEB This drawing is for Breakaway Ground Mounted Signs on I Beam Posts, this drawing has a table showing the post type required to support a specified sign area Installation of Signs (drawings) The following typical drawings for sign installation are included in the Departments Traffic Control Standards Manual and are attached for reference: - Drawing No. TEB 1.69, Typical Route Marker Cluster Board Assembly - Drawing No. TEB 1.70, Typical Sign Installation Height & Lateral Location - Drawing No. TEB 1.71, Typical Sign Assembly Detail - Drawing No. TEB 1.71A, C Cluster Frame - Drawing No. TEB 1.72, Typical Installation of Large Signs ( On Wooden posts) - Drawing No. TEB 1.75, Typical Installation of Large Signs ( On Steel I Beam Posts) - Drawing No. TEB 1.82, Breakaway Ground Mounted Signs on I-Beam Posts - Drawing No. TEB 1.83, Breakaway Ground Mounted Bases Steel I Beam Posts - Drawing No. TEB 1.95, Sign Assembly for Extruded Aluminum Panels Prepared by: Joe Filice December 17, 2003 Page 13 of 13