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A rollsign on the MBTA Red Line in Boston. This sign has a hand crank to change the destinations displayed, but many rollsigns are motorized.


A rollsign, roll sign, destination blind or indicator blind is a mechanical display used to indicate a transport vehicle's route number and destination. Still-other alternative names include "curtain sign", "bus blind" and "destination film". A specific type of destination sign, rollsigns are commonly seen in older public transport vehicles, but are sometimes still used in modern vehicles. Since the 1980s, they have largely been supplanted by electronic signs,[1] using a digital display, which are somewhat less-readable but have the advantage of being easier to change between routes/destinations and to update for changes to a transit system's route network. However, the long life of public transit vehicles and of the sign rolls, if well made, means that many transit systems continue to use these devices. Also, while electronic flip-disc or LED signs are the norm on newer buses, some operators continue to prefer rollsigns for their fixed-track modes, such as trolleybuses, trams and subway/metro cars, because fixed-track networks tend to change less frequently, which lessens the value of one of the key advantages of electronic signs in such cases.

Contents

Design

Destinations or names of the route are printed on a long roll or blind, usually made of mylar, reinforced paper or Tyvek. The roll is attached to metal tubes at the top and bottom, and flanges at the ends of the tubes are inserted into a mechanism which controls the rolling of the sign or blind. The upper and lower rollers are postioned sufficiently far apart to permit a complete "reading" (a destination or route name) to be displayed, and a strip light is fitted behind the blind, so as to illuminate it at night.

Operation

A rollsign-equipped trolleybus in Arnhem, Netherlands

When the display needs to be changed, the driver/operator/conductor simply turns a handle/crank—or holds a switch if the sign mechanism is motorized—which engages one roller to gather up the blind and disengages the other, until the desired blind display is found. A small viewing window in the back of the signbox (the compartment housing the sign mechanism) permits the driver to see an indication of what display is being shown on the vehicle's exterior.

Two types of light rail car on the MAX system in Portland, Oregon, both fitted with rollsigns. This photo illustrates how rolls/blinds allow use of color and of symbols, such as the airplane icon shown here.

Automatic changing of rollsign/blind displays, through electronic control, has been possible since at least the 1970s, but is an option that primarily has been used on rail systems—where a metro train or articulated tram can have several separate signboxes each—and only infrequently on buses, where it is comparatively easy for the driver to change the display. These signs are controlled by a computer through an interface in the driver's cabin. Barcodes are printed on the reverse of the blind, and as the computer rolls the blind an optical sensor reads the barcodes until reaching the code for the requested display. The on-board computer is normally programmed with information on the order of the displays, and can be programmed using the non-volatile memory should the blind/roll be changed. These sign systems are normally accurate; however, over time the blind becomes dirty and the computer may not be able to read the markings well, leading occasionally to incorrect displays. For buses, this disadvantage is outweighed by the need (compared to manual) to change each destination separately; if changing routes, this could be up to seven different blinds. Automatic-setting rollsigns are common on many light rail and subway/metro systems in North America, and in the U.K. such capability is standard on the so-called "bendy buses" (articulated buses) of Transport for London (TfL) and in Citaro Gs, when equipped with blinds.

Materials used

For decades, heavy grade linen was the favourite material used for rollsigns/destination blinds, but today they are most commonly made of mylar or similar types of plastic film, which material is much more tear-resistant and longer lasting.[1] The old style linen blinds are quite collectible, and can fetch high prices at auctions and transport sales.

In the 1940s, London Transport started producing blinds that were made by sticking paper slips onto a linen backing. This method had the advantage that large numbers of destinations that were in use on a number of blinds e.g. "KINGS CROSS" or "TRAFALGAR SQUARE" could be screen printed and held pending demand. As time passed the blind department in Chiswick gave way to cost cutting and now all LTs blinds are produced by McKenna Brothers of Middleton, Greater Manchester. They use a computerised system of printing the blinds directly onto tyvek, a type of fibrous paper material that has extremely resilient qualities. They were produced for operators all over the UK and use the distinctive London Transport-designed Johnston typeface which is similar to Gill Sans but with minor variations. This typeface has been in use for almost 70 years.

References

  1. ^ a b "Sign of the Times: Transit signs have evolved from curtain signs to the first electronic sign introduced by Luminator to the present ADA-regulated visual and audio signs". Mass Transit magazine, January-February 1993, pp. 30-32. Fort Atkinson, WI (USA): Cygnus Publishing. ISSN 0364-3484.

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