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Last edited 24 Aug 2016

Types of road and street

Highway-1277246 640.jpg


[edit] What is the difference between a road and a street?

In the Manual for Streets (2007), the Department for Transport (DfT) gives a clear definition of streets and roads:

  • Roads are essentially highways whose main function is accommodating the movement of motor traffic.
  • Streets are typically lined with buildings and public spaces, and while movement is still a key function, there are several others, of which the place function is the most important.

[edit] Balancing ‘place’ and ‘movement’

‘Place’ and ‘movement’ are the two fundamental components of street design, with place being given priority above movement. The SCOTS National Roads Development Guide (NRDG) defines this relationship as:

  • ‘Place status denotes the significance of a street, junction or part of a street and therefore consideration of place is considered critical in the design of good transport networks.’
  • ‘Movement is activity and can be expressed in terms of traffic volume and strategic importance of the street, or section of that street, it also considers other street users such as pedestrians and cyclists.’

All roads and streets should be planned and designed from this perspective. For example, Designing Streets (2010) explains that defining the relative importance of particular streets/roads in terms of place and movement functions should inform subsequent design choices.

For example:

  • Motorways: High movement function, low place function.
  • High streets: Medium movement function, high place function.
  • Residential streets: Low to medium movement function, medium to high place function.

When engineers design streets, there are a range of minimum standards required to guide safe and efficient passage for various types of street users.

Manual for Streets (2007) explains that street character types in new residential developments should be determined by the relative importance of both their place and movement functions. The NRDG also state that a street layout which fails to recognise the street character types and frequency of its users is also likely to fail with regard to the wider structure of the street network.

Any street, whilst considering place before movement, must balance all associated functions and considerations to deliver a sustainable and adaptable outcome.

[edit] Road types

There are several types of road with individual and specific functions. Designing Streets (2010) provides a summary of the individual road types:

[edit] Primary

[edit] Strategic roads

These provide for major traffic movement between centres of population and economic activity on a national and regional level.

[edit] Main roads or primary streets

Within urban boundaries these link traffic from strategic roads to residential streets or industrial roads. They include ‘arterial’ through routes and mixed-use, multi-functional ‘high streets’ (at least in part along their length), providing access to properties as well as other amenities. Likely to be public transport routes they require a careful balance of place and movement when improving or connecting into with new development.

[edit] Secondary

[edit] Residential streets

Provide access to properties and through routes within a residential area. As secondary connectors they are much less likely to be public transport routes.

[edit] Residential and service lanes

These solely provide access to properties within a residential area. These tertiary streets could be mews, vennels, or courtyards.

[edit] Industrial roads

Link multi-functional industrial/commercial premises and associated parking and service areas to main or strategic roads. When within urban boundaries some elements of Designing Streets may be applied, dependent on context and an assessment of future adaptability, but the balance is towards vehicle movement.

[edit] Tertiary

Other routes, not for motor vehicles include:

  • Footways: A pedestrian route that adjoins a carriageway.
  • Footpaths: A pedestrian route not adjoining a carriageway.
  • Cycleways: A cyclist route that adjoins a carriageway.
  • Cycle track: A cyclist route not adjoining a carriageway.
  • Shared surfaces: Low trafficked single level street that serves a range of user types, normally limited to residential streets where traffic speeds do not exceed 10 mph.

[edit] Motorways

A motorway is a strategic road for major traffic movement between centres of population and is classified in England as a ‘special road’ – a road where certain types of traffic are prohibited.

[edit] Primary Route Network (PRN)

The PRN, in England, designates roads between places of traffic importance across the UK, with the aim of providing easily identifiable routes to access the whole of the country (DfT, 2012). The PRN is constructed from a series of locations (primary destinations) selected by the Department for Transport, which are then linked by roads (primary routes) selected by the local highway authority.

The PRN is a devolved matter. Several primary routes run between England and Scotland or England and Wales, meaning cooperation between highways bodies across borders is required. The criteria for defining a primary destination are purposefully flexible, in order to allow the PRN to serve the whole of the country.

All primary routes consist of an A road or sequence of A roads, forming a continuous route between two primary destinations. All UK roads (excluding motorways) fall into the following four categories:

[edit] A roads

Major roads intended to provide large-scale transport links within or between areas.

[edit] B roads

Roads intended to connect different areas, and to feed traffic between A roads and smaller roads on the network.

[edit] Classified unnumbered

Smaller roads intended to connect together unclassified roads with A and B roads, and often linking a housing estate or a village to the rest of the network. Similar to ‘minor roads’ on an Ordnance Survey map and sometimes known unofficially as C roads.

[edit] Unclassified

Local roads intended for local traffic. The vast majority (60%) of roads in the UK fall within this category.

This article was first published by ICE on 30 March 2016 as ‘Which highway and why? An overview of roads, streets and their purpose’. Written by Adam Kirkup.

--The Institution of Civil Engineers

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