Route informatory signs are horizontal signs which guide the driver to the desired destination. Such signs which are correctly designed, made & mounted, cause more safety & simplicity for the passing traffic. These signs are classified as per their mounting location as follows:
Since there is a short distance between entrances & exits of urban highways, usually only two signs for route selection & exit signs are used. On the other hand, due to limitations on the sides of urban routs (green spaces, residential areas, etc.), these signs are usually mounted as overhead.
These are signs which are mounted in advance of the destination & inform the drivers of exits & normally mounted on the right hand side of the road & if any emphasis is required, they can also be repeated on the left side.
These signs help the driver to change his lane in time. These are usually mounted after pre-informatory & before exit signs. These are usually mounted as overhead signs.
Exist signs are mounted at exits & show the exit route. These are mounted on the island between the two routes. Where the island width is lass than the sign width or there is not enough visibility for the drivers, these are mounted as side – overhead or cross – post signs.
These are signs which are mounted on the new selected route to ensure the driver that the right route has been selected. On the inter – city roads, information such as road number & distance to the next city is also show on the sign. These signs are mounted on the right side of the road.
The following diagram depicts this fact. As is clear from the diagram, in order to compensate the loss of reflectivity in overhead & right side mounted signs, larger sign dimensions & higher reflectivity sheetings must be used. Where the right side of the road provides suitable space for mounting of the sign, mounting as overhead must be avoided.
Dimensions of route informatory signs depend on the design speed. The computerized design stage, height of local language letter for A is first selected on the basis of the design speed & dimensions of the sign are derived after completion of this design stage.
SELECTION OF THE
DIMIENSIONS WITHOUT CONSIDERING THE DISIGN SPEED AND NUMBER OF ROUTES, IS A COMMON MISTAKE WHICH IS FREQUENTLY REPEATED.
It must be noted that design of these signs needs special expertise which is out of the scope of this booklet. Selection of a suitable alphabet (font) s one of the necessities of the design stage.
It must be readable from the desired distances (readability principle)
It must be quickly understandable (wording principle)
Important & first class destinations must be mentioned (priority principle)
Names must be repeated on next signs (consistency principle)
Design beauty & suitability of sign dimensions must be obeyed (beauty principle)
On any route, the colour of the background & wording depends on the type of the route as per the following classification. Routes & destinations of higher priorities, keep their allocated colour.
It is strongly recommended that Engineer Grade material must be used for these signs. It is not an exaggeration to state that application of Engineer Grade material for this purpose is a waste of money. Three main advantages of High Intensity material, namely reflection value, suitable visibility angle (up to 60 degrees) & long life (over 15 years) confirms this statement.
Metal used for the body of guidance signs is usually of two types. Large signs are made of rails. These metal rails have 20cm usable width & these are assembled together on the mounting location of the sign. The sheets are galvanized & have 1.25mm thickness or aluminium of 3mm thickness. The advantage of this method is low transport cost & simpler future maintenance. In smaller signs, a unified frame is made & then a galvanized sheet of 1.5mm thickness in connected on the top of the frame. This method is usually called unified sign manufacture. In both methods, all necessary accessories for connection to the sign post must be prepared to reduce labour hours on welding & final mounting.
Posts for these signs are calculated as proportional to the wind surface of the sign & can not be estimated prior to the design of the sign. As an estimate, for each square meter of sign surface, 16 to 24kg weight of post is required. Posts are metal boxes or structures of metal boxes. In special circumstances, multi -sided sheets with industrial paint coatings are used for side – overhead signs.
