Section 3: Freeway Signing Terminology
Anchor: #i1002318Introduction
This section defines various terms commonly used in freeway signing. In some cases, these terms are used to classify design guidelines that appear in this handbook or documents such as the Texas MUTCD.
Anchor: #i1002328Texas MUTCD Interchange Classification Scheme
The 2003 Texas MUTCD classified interchanges as described below. These classifications were used by the Texas MUTCD to recommend letter heights for freeway guide signs and to determine the number of Advance Guide signs that should be used in advance of the exit. However, the next subheading simplifies the 2003 Texas MUTCD interchange classification scheme for designing freeway guide signs. The interchange classifications are as follows:
Major Interchange — There are two types of major interchanges:
- Category A — Interchanges with other expressways or freeways.
- Category B — Interchanges (other than freeway or expressway interchanges) with high-volume multilane highways, principal urban arterials, and major rural routes where the volume of interchanging traffic is heavy or includes many road users unfamiliar with the area.
Intermediate Interchanges — Interchanges with urban and rural routes not in the category of major or minor interchanges.
Minor Interchanges — Interchanges where traffic is local and very light, such as interchanges with land service access roads. Where the sum of exit volumes is estimated to be lower than 100 vehicles per day in the design year, the interchange is classified as minor.
This interchange classification scheme is overly complicated, difficult to apply, and was not included in the 2006 Texas MUTCD. For the purposes of this handbook, the scheme has been simplified as described in the following subheading.
Anchor: #i1002367Freeway Signing Handbook Interchange Classification Scheme
The Texas MUTCD classification scheme (described in the preceding subheading) is somewhat difficult to apply to many interchanges, and the differences are not typically significant. For the purposes of this handbook, the interchange descriptions have been simplified to address the following design considerations:
- guide sign letter height
- number of Advance Guide signs.
Guide Sign Letter Height. The letter height guidelines provided in Table 2E-2 of the Texas MUTCD have been simplified so there is only one minimum letter height option. As a result, it is not necessary to distinguish between interchange types to determine the appropriate letter height. Larger letter heights may be appropriate in some situations.
Number of Advance Guide Signs. The Texas MUTCD requires one Advance Guide sign for minor interchanges. Two, and preferably three, Advance Guide signs are used for other interchanges. The following definition of a minor interchange (requiring only one Advance Guide sign) is based on the Texas MUTCD definition of a minor interchange.
Minor Interchange — An interchange where all traffic exiting the freeway at the interchange (for all exits at the interchange from both directions) is estimated to be 100 vehicles per day or less in the design year (typically 20 years into the future).