Phinma – University of PangasinanCollege of Engineering and Architecture

Traffic Engineering

•Road and Traffic Signs•

Engr. Henry T. AmadoInstructor

Marc Dared F. CagaoanResearcher

Background:

A standardized road traffic system is essential to ensure that drivers acquire the information necessary to enable them to comply with road regulations and to navigate their way around the road system in a safe and efficient manner.

As in the case of any other type of traffic control devices, road signs should be used only when these are necessary and where their use has been justified by field studies.

Road signs contain instructions that the road user is required to obey. They warn the road user of hazards that may not be self-evident. They also give information about routes, directions, destinations, and places of interests. Since road signs are essential part of the road traffic system, their message should be concise, meaningful, consistent, and their design and placement must be coordinated with the road geometric design.

Classification of Road Signs:

Signs are classified in the following groups according to their use.

Regulatory signs Warning signs Guide signs or informative signs

Design:

Uniformity in the design of signs facilitates identification by the road user. Standardization of shape, color, dimensions, legends and illumination or reflectorization is important so that various classes of signs can be easily recognized. The following general design principles have evolved:

The driver should not be unduly distracted from his task of driving by reading a traffic sign. A traffic sign should be perceived and understood by the driver traveling at the 85% percentile

speed of the traffic on the road, in sufficient time for him to safely take any action necessary.

Shape:

Standard sign shapes are:

The octagon is reserved exclusively for the STOP sign; The equilateral triangle, with one point vertically downward is reserved for the GIVE WAY Sign; The circle symbol is mainly used for regulatory signs; The circle symbol may sometimes be mounted on a rectangular base either for easy recognition

or for additional information; The equilateral triangle with one point vertically upward is used for warning signs; The rectangle, usually with long axis horizontal is used for directional signs, service signs, road

work signs, signs for special purposes, and supplementary plates for warning signs; The rectangle, usually with long axis vertical is generally used for facility information signs,

instruction signs, guide signs, and destinations of point of interest; and, The pentagon, with point up is used only for pedestrian and school crossing sign.

Color:

The standard colors for signs are as follows:

Red is used as a background for STOP signs, as border color on GIVE WAY signs, warning signs and prohibitive signs in the regulatory type.

Black is used as legend color for signs having white, yellow, orange, fluorescent orange, fluorescent yellow green background and as chevron for hazard markers.

Yellow is used as background color for roadwork signs. White is the background color for most signs and legends for some colored background. Fluorescent yellow green is used as background color for signs related to pedestrian movement,

school zones, and road work hazard markers to give additional emphasis and guidance to vehicle operators.

Fluorescent orange is used as background color for roadwork signs whose legends relate to personnel working.

Green is used as background color for direction signs. Blue is used as background color for service signs. Brown is reserved as background color for all tourist facility directional and information signs.

Sizes:

Minimum dimensions depend upon applications. Larger sizes are required for wider roadways and on high-speed facilities.

Uniformity of Location:

Signs are normally located on the right side of the road. In special circumstances, which are specified herein, signs may be duplicated on the left side or mounted over the road. If the sign is located at an exposed position, consideration may need to be given to the use of a frangible or breakaway type of construction, or other means of safety protection for the road user at the sign supports.

Longitudinal Placement:

The longitudinal placement of certain signs is fixed by the nature of their message or their characteristic use. Special care is required in the sitting of such signs to ensure that they are prominently displayed to approaching drivers. Signs that give advance warning or information should be located sufficiently in advance to enable the driver to react appropriately.

Generally, there should not be more than one signs of a particular type on each post, except where one sign supplements another, or where route or directional signs must be grouped. Where it becomes necessary to convey two or more different messages at one location, separate signs located at a minimum of 0.6Vm apart (where V is the 85th percentile speed in kph) should be used. For guide signs on expressways and other high speed roads considerable greater distance may be required. Such signs should not obscure or detract from one another.

Lateral Placement and Height:

The following subsections are the general rules for the lateral location of roadside signs and for the mounting heights on roadside. The lateral placement is measured from the edge of the sign nearest the road and the height from the underside of the lowest sign. The rules apply to permanent signs and include signs for roadwork and special purposes where these are mounted on posts set into the ground. Any variation in these rules for a particular sign is given in the rule relating to that sign. There are, however, be exceptions where conditions do not permit these rules to be applied. In these cases, the placement or height is adjusted to meet these special conditions e.g., the height of a sign may be increased or decreased to avoid obstructing sight distance at an intersection.

a. Rural Areas

Lateral Placement: On uncurbed roads in the rural areas, the sign should be at least 600mm clear of the outer edge of the road shoulder, the line of the guideposts or face of guardrail. The clearance should not be less than 2m nor more than 5m from the edge of the traveled way, except for large guide signs on expressways where great clearances may be required.

Height: In rural areas, roadside signs should be mounted clear of roadside vegetation and clearly visible under headlight illumination by night. The height of the sign should normally be between 1m and 1.5m above the nearest edge of traveled way. For fingerboards and intersection direction signs, the height should be increased to 2m.

b. Urban Areas

Lateral placement: On curbed roads, signs should be located back from the face of the curb not less than 300mm nor more than 1m. Where mountable or semi-mountable curbs are used e.g., on traffic islands, the minimum clearance should be 500mm. On uncurbed roads or on certain arterial roads designed for high speed traffic movement, the distance given in Rural Areas shall be used.

Height: On curbed roads, the signs should be set at a minimum of 2m above the top of the curb to prevent obstruction to pedestrians. Where neither pedestrians nor parked vehicles have to be considered, e.g., on a traffic island or median, the height given for rural areas shall be used. Signs that overhang a footway should have height of 2.5m with a minimum height of 2m above the level of the footway.

The recommended lateral positioning of road side signs are shown in Figure 1.1.

Figure 1.1: Later Positioning of Road Side SignsOverhead Signs:

The operational requirements of our highways and expressways are such that overhead signs will have to be provided at many locations.

The following conditions should be considered in the erection of overhead sign displays:

Traffic volume at or near capacity; Complex or closely spaced interchanges; Three or more lanes in each direction; Restricted sight distance; Multi-lane exits; Large percentage of trucks; Street lighting background; High speed traffic; Consistency of sign message location through a series of interchanges; and, Insufficient space for ground mounted signs.

Reflectorization and Illumination

Signs that are intended to convey message during dark periods need to be reflectorized or illuminated for greater visibility of colors and shapes. High- grade reflective or illuminated materials shall be required on overhead signs and for road signs in areas with street lighting of high intensity

Regulatory Signs

Regulatory signs indicate the application of legal or statutory requirements, e.g., obligation to give way at intersections, speed limits, prohibition of movements at intersections and control of parking of vehicles.

Most regulatory signs are rectangular in shape, with either red or black legend on a generally white background. The notable exceptions to this are STOP signs (octagonal), GIVE WAY (triangular) and some manually operated banner used in road works.

Regulatory signs shall be erected only with the approval of the Secretary of the DPWH or delegated authority on national roads and their intersecting roads or local government authority having the necessary jurisdiction, and shall be removed promptly if the legal requirements of the signs become inconsistent with the prevailing conditions.

Warning Signs

Warning Signs are used to warn motorists of potentially hazardous conditions on or adjacent to the road. The Warning Signs advise motorists of road conditions that require caution and may call for a reduction in speed, in the interest of safety and that of other road users.

Warning signs tend to lose their effectiveness if used unnecessarily or too frequently. Their use should be restricted to the minimum, consistent with safety. A warning sign should not be used when drivers can observe and appreciate the potential hazard ahead under normal conditions.

Guide Signs or Informative Signs

Guide signs inform road users about the direction and distances of destinations on the route they are following or along other roads that intersect their route. They also supply information to identify points of geographical or historical interest and give directions to rest areas, camping or parking areas.

Guide signs do not normally lose their value by frequent use but they can be ineffective unless attention is given to their proper location and the clarity of the message.

Shape:Guide signs are generally rectangular in shape. Where practicable, they should be designed with

long axis horizontal. Exceptions to this rule are route markers, which are normally on a shield of distinctive shape and kilometer posts.

Color:The words, symbols, and borders of guide signs should be reflectorized on all colors except black

that contrasts with the background of the sign. The background color should be easily recognizable by motorists as being applicable to the particular category of guide signs for which it is used. The color combinations, which shall be used are as follows:

Black legend on white background: Information signs, street name signs and kilometer posts; White legend on standard green or blue background: Advance direction signs, intersection and

special direction signs, and re- assurance direction signs, including signs giving directions to expressways from the adjacent road and street system;

White legend on blue background: Signs indicating roadside facilities, services and legends used. The size adopted will depend on the required letter size, the number of words in the legend, symbols used and the general arrangement;

White legend on brown background: Tourists interests;

Size:Standardization of guide sign size is not always practicable due to the variety of legends used.

The size adopted will depend on the required letter size, the number of words in the legend, symbols used and the general arrangement.

The likely visual impact of the sign must be considered in relation to its location, background and surroundings. For example, in an urban street with advertising signs, guide signs may need to be increased in size to compete effective with adjacent signs. Overhead signs need to be larger than signs mounted in normal positions at the side of a road, while roads, which carry predominantly high-speed traffic, require larger signs than low-speed roads.

Special attention should be given to single-name direction signs having short names to ensure that the visual impact of the sign is not lost by economizing on its overall size.