Road hierarchy: Difference between revisions

Revision as of 18:59, 2 May 2025

Latest revision as of 23:32, 1 June 2025

(4 intermediate revisions by 3 users not shown)

Line 7:

A '''road hierarchy''' is a system for categorizing [[road]]s. Road networks worldwide are typically organized according to one or more schemes:

* ''Functional classification'' reflects a road’s intended role, balancing mobility (efficient through movement) and access (reaching properties) by defining a clear hierarchy from [[Arterial road|arterial]]s (including [[expresswaylimited-access road]]s and [[controlled-access highway]]s) to [[Collector road|collector]]s and local roads.<ref name="fhwa-functional-classification"/><ref name="erso-classification"/>

* ''Administrative classification'' mirrors government tiers responsible for funding and maintenance, creating a hierarchy from national to local roads.

* ''Design type classification'' groups roads by [[Geometric design of roads|geometric]] and operational characteristics, such as lane configuration and access control, and does not always form a strict hierarchy.<ref name="aashto-functional-classification"/><ref name="erso-classification"/>

Line 20:

==== Controlled-access highway ====

At the top of the mobility-access continuum in terms of traffic flow and speed are [[controlled-access highway]]s;. theirTheir defining characteristic is the ''control of access'' to and from the road, meaning that the road cannot be directly accessed from properties or other roads, but only from specific connector roads. This indirection, in conjunction with high speed limits and multiple lanes, allows these roads to support fast traffic flow with high volume, in both urban and rural areas. They are at the bottom of the mobility-access continuum in terms of access to property, allowing access to almost nothing besides other roads and [[rest areas]].

They are also known as ''freeways'' in the U.S., South Africa, and parts of Australia; as ''motorways'' in the U.K., New Zealand, and parts of Australia; and as ''expressways'' in numerous countries (though this term sometimes includes [[limited-access road]]s depending on the region).

Line 38:

==== Limited-access road ====

[[File:Route nationale 137 à La Rochelle · Périgny (17, France).JPG|thumb|Dual carriageway near [[La Rochelle]], France]]

A [[limited-access road]], also known as ''limited-access highway'' in the U.S. and as [[controlled-access highway|''expressway]]'' in numerous countries (including parts of the U.S.), is similar to a controlled-access highway in that it conforms to many or most of the standards that controlled-access highways follow, but does allow some uncontrolled access to local roads. They can be viewed as a middle ground between controlled-access highways and minor arterial roads. The degree of isolation from local traffic varies between countries and regions, as does a precise definition of the term itself.

Controlled-access highways can also be viewed as a subset of limited-access highways that has stricter requirements.

Line 72:

Many countries may have more than one national highway system of a lower rank, such as the [[U.S. Highways]] (not to be confused with the Interstate system), only portions of which run on controlled-access highways. Conversely, there may also be controlled-access highways not part of a numbered system. Highways are usually given icons featuring the number of the highway called [[Highway shield|highway shields or route markers]]. In addition to the national highway system, there may be provincial-level or state-level (US) highway systems of a lower rank, which need not consist mainly of controlled-access highways.

== United States and Canada ==

[[File:Us-vmt-by-functional-system.png|thumb|440px|[[Vehicle miles of travel]] by highway functional system in the US]]

Line 96:

* Local roads and streets

[[arterial road|Arterials]] are major through roads that are expected to carry large volumes of traffic. At the top of the mobility-access continuum, they include [[freeway]]s, whose on- and off-ramps enable operating with less friction at a high speed with high flow. In some places, arterials include large divided roads with few or no driveways that cannot be called freeways because they have occasional at-grade intersections with [[traffic lights]] that stop traffic (expressways in [[Limited-access road|expresswaysCalifornia]], inwhich are [[Californialimited-access roads]]) or they are just too short (superarterials in [[Nevada]]). [[Frontage road]]s are often used to reduce the conflict between the high-speed nature of an arterial and property access concerns.

[[collector road|Collector]]s, collect traffic from local roads, and distribute it to arterials. Traffic using a collector is usually going to or coming from somewhere nearby. They should not to be confused with [[collector lane]]s, which reduce [[Grade separation#Weaving|weaving]] on freeways.

Line 111:

Otherwise, most other European countries have some form of differentiating between national routes, regional and inter-regional roads and other local routes.

===Comparison of symbols and names===

Here there is a table comparing the symbols and generic names of the various route types in Europe. Not shown are the expressways ([[limited-access road|expressways]]s) and municipal-level routes, as these categories seldom have specific signage. Some countries have two categories of secondary routes, in which case they are shown here in hierarchical order.

{| class="wikitable" style="text-align:center;"

|-

Line 442:

==External links==

* [https://web.archive.org/web/20011111044214/http://www.fhwa.dot.gov/environment/flex/ch03.htm FHWA - Functional Classification]{{Obsolete source |reason=There are two more recent editions with significant changes.|date=April 2025}}

* {{cite report |author=European Road Safety Observatory |date=2018 |chapter=Road classification |title=Roads |url=https://road-safety.transport.ec.europa.eu/system/files/2021-07/ersosynthesis2018-roads.pdf |edition=2018 |publisher=European Commission |pages=5-65–6 |url-status=live |archive-url=https://web.archive.org/web/20220625043417/https://road-safety.transport.ec.europa.eu/system/files/2021-07/ersosynthesis2018-roads.pdf |archive-date=25 June 2022}}

* {{cite book |date=2006 |chapter=From theory to vision: Functional road categorization |___location=Leidschendam |editor-last1=Wegman |editor-first1=Fred |editor-last2=Aarts |editor-first2=Letty |title=Advancing Sustainable Safety: National Road Safety Outlook for 2005-2020 |translator-last1=Bastiaans |translator-first1=René |translator-last2=Breen |translator-first2=Jeanne |edition= |publication-place= |publisher=SWOV Institute for Road Safety Research |pages=37-3837–38 |isbn=978-90-807958-7-7}}

{{Road types}}