scope:

SCOPE AND INTRODUCTION

The goal of this standard is to provide the user with safe, dependable, functional, and easily maintained Dynamic Message Sign (DMS) equipment.

The requirements of this standard were developed by industry consensus, taking into account current user needs, available commercial technologies, engineering research, traffic engineering applications, human factors engineering, and engineering judgment.

NEMA Bylaws require the periodic review and updating of this standard. Further updates should include the evaluation of new technologies and research.

Original quantitative research is not within the scope or resources of this committee. Said research by others is encouraged and should be considered by the reviewing committee in support of the updating process.

The scope of this document is to define the minimum hardware and functional characteristics of electronically controlled Dynamic Message Signs used for displaying messages to travelers.

The intent of this standard is to eventually accommodate all subsets of the DMS family. However, this initial version predominantly addresses the Variable Message Sign subset.

In preparing this standard, the committee began with a very comprehensive and encompassing scope of work that was later trimmed so the standard could be released at an earlier date. For almost every element described, arguments could be made to include additional information or less information.

Rather than debate these issues internally and eternally within the Committee, the consensus was that greater benefit would be served from end user input derived through a first implementation of a standard with a reduced scope. With this in mind, the committee anticipates that a second, market driven version of this standard will include further end user input discovered from implementations and other work on the items intentionally tabled from this version.

In all cases, the goal was to avoid, as much as possible, "specification" language that detailed how an item must be built, in favor of "standards language" that addresses functionality. At the same time, the committee realized its obligation to the end users to assure that requirements for safety, dependability, and maintenance are met, so details are often listed that were derived from many field implementations currently in use.

While the Committee also attempted to keep the language open enough for development of newer technology, because representation and input from any newer technologies was not received to date, the committee focused on existing technologies currently used. As new technologies emerge, this standard can still be used as a benchmark, whereby the developers of new technologies should be able to show either their compliance to the requirements of the standard, or how the newer technology exceeds the intent of this standard. Once a newer technology is tried, used and accepted by end users or other third party agencies, representatives of newer technology should participate in future revisions and versions of this standard through the NEMA standards development process.

This standard is not meant to apply to any one piece of equipment or to any one manufacturer. Likewise, it is not intended that any one piece of equipment will meet all the requirements of this standard. The standard is intended as a menu of features that are available to the end user. Conformance to the standard is defined in Section 11.

It is anticipated that end users will include the desired references or parts of this standard as part of their procurement specifications. In addition, the end user can require any other features they may choose outside of these requirements as part of their hardware procurement specifications.

Those areas of this standard marked as TBD (To Be Determined) are identified by the Committee as warranting attention in this standard, but for reasons of time were tabled for future versions. The lack of the TBD designation is not meant to preclude inclusion of any item in any future revision.

This standard is not intended to be, or is meant to take the place of any application guides for DMS. Items such as sign siting practices, selection of character heights, siting of cabinets and relations between legibility and travel speed, etc were all considered by the committee to be outside the scope of this document.