Editing Variable-message sign (section)

==Technologies and types==
Early variable message signs included static signs with words that would illuminate (often using neon tubing) indicating the type of incident that occurred, or signs that used rotating prisms ([[trilon]]s) to change the message being displayed. These were later replaced by dot matrix displays typically using [[eggcrate display|eggcrate]], [[fiber optic display|fiber optic]], or [[flip-disc display|flip-disc]] technology, which were capable of displaying a much wider range of messages than earlier static variable message signs. Since the late 1990s, the most common technology used in new installations for variable message signs are [[LED display]]s. In recent years, some newer LED variable message signs have the ability to display colored text and graphics.

Dot-matrix variable message signs are divided into three subgroups: character matrix, row matrix, and full matrix. In a character matrix VMS, each character is given its own matrix with equal horizontal spacing between them, typically with two or three rows of characters. In a full matrix VMS, the entire sign is a single large dot matrix display, allowing the display of different fonts and graphics. A row matrix VMS is a hybrid of the two types, divided into two or three rows like a character matrix display, except each row is a single long dot matrix display instead of being split per character horizontally.

Overhead variable message signs are today available in three form factors: front access, rear access, and walk-in. In a front access variable message sign, maintenance is performed by lifting the sign open from the front. Most smaller VMS are of the front access form factor, and are typically installed today on major arterials. The rear access form factor is similar to the front access form factor, except that maintenance is performed from the rear of the sign, and are commonly used for medium-sized dynamic message signs installed along the roadside of freeways (instead of overhead). The walk-in form factor is a more recent introduction, where maintenance on the sign is performed from the inside of the sign. A key advantage of the walk-in form factor is that lane closures are generally not required to perform maintenance on the sign. Most of the largest VMS units installed today are walk-in units, and are typically installed overhead on freeways. {{citation needed|date=March 2024}}

The NJ Turnpike Authority counts five unique types of variable message signs under its jurisdiction, at least one of which has been replaced by newer signs.<ref>{{Cite web |url=http://www.nj.gov/turnpike/documents/VMS_Guide_031912.pdf |title=Archived copy |access-date=2016-06-01 |archive-date=2015-09-10 |archive-url=https://web.archive.org/web/20150910232933/http://nj.gov/turnpike/documents/VMS_Guide_031912.pdf |url-status=dead }}</ref> They are:

#"REDUCE SPEED" neon signs (1950s-2010, obsolete, have now been replaced).
#"Changeable message signs" (trilon/ rotating-drum signs that can be used for closing roads or moving traffic to other roadways).
#Electronic VMS: signs with remotely controlled messages displayed on them; the messages are sent from the State Traffic Management Center, updating the signs automatically.
#Variable speed limit signs - used for varying the posted speed limits within work zones and in emergencies.
#Portable VMS: movable "electronic VMS". A portable VMS has much the same characteristics as a fixed electronic VMS, but can be moved from location to location as the need dictates.