white and blue truck on gray pavement road

white and blue truck on gray pavement road



Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduced, for example, the fingerposts in the United Kingdom and their wooden counterparts in Saxony.
With traffic volumes increasing since the 1930s, many countries have adopted pictorial signs or otherwise simplified and standardized their signs to overcome language barriers, and enhance traffic safety. Such pictorial signs use symbols (often silhouettes) in place of words and are usually based on international protocols. Such signs were first developed in Europe, and have been adopted by most countries to varying degrees.
In the United States, the categories, placement, and graphic standards for traffic signs and pavement markings are legally defined in the Federal Highway Administration's Manual on Uniform Traffic Control Devices as the standard.
A rather informal distinction among the directional signs is the one between advance directional signs, interchange directional signs, and reassurance signs. Advance directional signs appear at a certain distance from the interchange, giving information for each direction. A number of countries do not give information for the road ahead (so-called "pull-through" signs), and only for the directions left and right. Advance directional signs enable drivers to take precautions for the exit (e.g., switch lanes, double check whether this is the correct exit, slow down). They often do not appear on lesser roads, but are normally posted on expressways and motorways, as drivers would be missing exits without them. While each nation has its own system, the first approach sign for a motorway exit is mostly placed at least 1,000 metres (3,300 ft) from the actual interchange. After that sign, one or two additional advance directional signs typically follow before the actual interchange itself.
New generations of traffic signs based on electronic displays can also change their text (or, in some countries, symbols) to provide for "intelligent control" linked to automated traffic sensors or remote manual input. In over 20 countries, real-time Traffic Message Channel incident warnings are conveyed directly to vehicle navigation systems using inaudible signals carried via FM radio, 3G cellular data and satellite broadcasts. Finally, cars can pay tolls and trucks pass safety screening checks using video numberplate scanning, or RFID transponders in windshields linked to antennae over the road, in support of on-board signalling, toll collection, and travel time monitoring.
Yet another "medium" for transferring information ordinarily associated with visible signs is RIAS (Remote Infrared Audible Signage), e.g., "talking signs" for print-handicapped (including blind/low-vision/illiterate) people. These are infra-red transmitters serving the same purpose as the usual graphic signs when received by an appropriate device such as a hand-held receiver or one built into a cell phone.
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