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Glossory

Glossary of terms used in the report

 Novermber 1963    The Buchanan Report    Glossory  
Contents • Glossory
Accessibility

The degree of freedom for vehicles to circulate and to penetrate to individual destinations and to stop on arrival. Two kinds of accessibility are distinguished—accessibility within an environmental area, and accessibility between different parts of a town and points beyond.

Access road
A road for giving direct access to the land or premises on either or both its sides.
Assign, assignment
When estimating traffic flows between two localities, and there is a choice of route available, then an assignment to the various alternatives must be made. It will be based on journey times, knowledge of preferences, presence of danger-spots and bottle-necks, etc.
By-pass
A road which enables through traffic to avoid a locality through which it would otherwise be obliged to pass.
Commuter
A person who makes a regular daily return journey between two places, usually between home and workplace in morning and evening. (Originally, a season ticket holder who paid a commuted sum in lieu of daily tickets).
Comprehensive development (or redevelopment)
The complete development or redevelopment of a sizeable area as a phased operation in accordance with a comprehensive plan for the whole area.
Corridor street
A street as defined below, where the buildings are arranged in continuous rows on both its sides.
Cost-benefit study
A type of study designed to ease the burden of decision between various alternative possible measures involving differing expenditures and differing degrees of benefit.
Crude capacity
The capacity of a street or an area to accommodate moving and stationary vehicles without regard to the need to maintain environmental standards.
Density
In town planning, the number of people or the amount of accommodation per unit area of ground. The density of residential areas is usually expressed in terms of people or rooms per acre, and may be gross or net according to whether ancillary uses such as school sites and public open space are included. The density of business and commercial areas is usually expressed in terms of plot ratio (ratio of total floor space to total plot areas excluding local access roads) or floor space index (ratio of total floor space to total area of sites including local access roads).
Desire line, desire line diagram
A desire line is a straight line drawn on a map between two points to indicate a desire for a journey to be made between those points. It does not indicate the actual route of the journey. Desire line diagrams are used in practice to summarise the desires for movement between specified zones, lines between identical zones being grouped together so that the composite width of the group of lines is in proportion to the total number of desired movements.
Development
Except where used in this Report in connection with the statutory planning system, development means buildings or the use of land for the erection of buildings. In relation to statutory planning it means (as defined in the 1962 Town and Country Planning Act) the carrying out of building, engineering, mining or other operations in, on, over or under land, or the making of any material change in the use of any buildings or other land.
Development control
The process by which a planning authority exercises its statutory duty to control all development (q.v.) in accordance with the provisions of the development plan. The control is enabled by virtue of the obligation upon all developers to seek planning consent for new development. Applications may be granted, granted with conditions, or refused. Aggrieved applicants may appeal to the Minister of Housing and Local Government.
Development plan
The statutory plan which all local planning authorities were required to prepare under the Town and Country Planning Act, 1947 (as superseded by the Town and Country Planning Act 1962) showing their proposals for the use and development of land for a period of approximately twenty years ahead, and which has to be reviewed at periods not exceeding five years.
Distributor hierarchy
The concept of distributor roads connecting one to another through an orderly sequence of function and importance, as the twigs of a tree connect to the branches, the branches to the limbs, and the limbs to the trunk. In this Report, national, regional, primary, district, and local distributors have been distinguished.
Distributor road
A road for the distribution of vehicles to areas of development, designed for efficient movement, and generally having no direct frontage access.
Distributory network
A continuously interconnected system of distributor roads. A primary distributory network is the network required in a town to give access to and between the main areas of development.
District distributor
See Distributor hierarchy, distributor road.
Environment
The term is used in two senses in this Report. First, in the normal way with reference to the general comfort, convenience, and aesthetic quality of the physical surroundings for living. Secondly, in a more specialised sense, where the term refers only to those aspects of the environment which are directly or indirectly affected by the presence of vehicles—moving or at rest—in urban areas.
Environmental area
An area having no extraneous traffic, and within which considerations of environment (in the specialised sense, as defined) predominate over the use of vehicles.
Environmental capacity
The capacity of a street or an area to accommodate moving and stationary vehicles having regard to the need to maintain the environmental standards.
Environmental management
A technique suggested in this Report whereby the environment of an area could be protected against the adverse effects of motor traffic by measures designed to prevent the entry of extraneous traffic and to re-organise internal flows so that they are less damaging in their effects. It is visualised as a technique which would be started without, in the early stages at any rate, heavy expenditure on capital works.
Environmental standard
A state of affairs defined as acceptable in relation to any or all of the direct or indirect effects of motor traffic on the environment.
Essential traffic
See Traffic-essential and optional.
Extraneous traffic
Traffic which has no reason to be in some particular locality apart from having been directed there, or come there of its own accord because no other route is available, or in response to congested conditions or lack of parking space elsewhere.
Floor space index
See Density.
Freeway
The American equivalent of a motorway. Other terms are also used for high-capacity roads, such as expressway, through-way, limited-access highway, some of which indicate varying standards of design.
Full car ownership
The state of affairs in any area when the ratio of cars to population ceases to show a material annual increase. For Britain as a whole it appears that this situation (known also as saturation level) may be reached in about 2010 when the ratio may stand at about 400 cars per 1,000 population.
Full use of cars
The unrestricted use of cars in conditions of full car ownership or saturation level.
Grade separation
A technical term to describe the carrying of one highway over or under another with or without facilities for interchange (q.v.). Fly-over and fly-under have the same meaning.
Individual transport
The movement of people in small vehicles holding only a very few persons, that is to say cars, taxis, motor cycles, etc.
Interchange
A system of interconnecting roadways in conjunction with grade separation providing for the interchange of traffic between two or more highways on different levels.
Lane
A longitudinal division of a carriageway intended to accommodate a single line of moving vehicles. A ‘six-lane highway’ would be one with three lanes of traffic in each direction. A reversible lane is one which may be used by traffic flowing in different directions at different times and is used to accommodate pronounced tidal flows.
Local distributor
See Distributor hierarchy, distributor road.
Motorway, motor road
A road reserved for certain classes of motor traffic only. As used in this country the term also signifies a road with no direct access to property and with grade-separated (i.e. fly-over or fly-under) intersections throughout. The term is thus much in the nature of a specification for a high-capacity road. Urban motorway is a motorway in an urban area.
New Town
As used in this Report, the term applies to urban development works undertaken under the New Towns Act of 1946.
Optional traffic
See Traffic-essential and optional.
Origin and destination survey
A survey for the purpose of ascertaining the origins and destinations of journeys.
Overspill
A term used to indicate the planned removal from an area of people or activities, usually with the object of relieving overcrowding or congestion.
Parking standard
In relation to the provision of parking space in new buildings, the number of parking spaces required to be provided by the developer at the behest of the local authority. Standards are usually expressed in relation to the size of the building or the type of activity carried on.
Passenger-car units (p.c.u.)
This term enables the capacity of a highway, or the volume of a stream of traffic, to be expressed in terms of a single number which is independent of the composition of vehicles in a traffic stream. It allows for the different effect of various types of vehicle by considering them in terms of the equivalent number of passenger cars. In practice the equivalents differ according to the layout of the section of the highway system under consideration, but for general purposes in this Report, the following values, appropriate to urban roads between inter-sections, have been adopted: Private cars and light vans… 10 p.c.u. Motor cycles… 0.75 p.c.u. Medium and heavy goods-vehicles… 2.0 p.c.u. Buses and coaches… 3.0 p.c.u.
Peak hour
Strictly, in respect of any road, the period of one hour's duration in the 24-hour day during which the greatest amount of traffic is carried. In practice, however, there may also be distinguished morning, midday or evening peak hours, whose meaning is clear.
Peak period
In a general sense, a period during the day when there is a pronounced movement of people or vehicles in any one direction or set of directions, over and above the normal level of activity.
Piecemeal development (or redevelopment)
Development which takes place by the building or rebuilding of single buildings on individual sites, as and when the market suggests the operation will be appropriate. Such development can take place according to an overall plan for the area, but the very fact that each building has to be capable of being constructed separately, places a severe restriction on the variety of architectural form that is possible, and on the extent to which the street system can be reorganised.
Plot ratio
See Density.
Precinct
An area reserved for pedestrians, all vehicles being excluded.
Primary distributor
See Distributor hierarchy.
Primary distribution network, primary network
See Distributory network.
Public transport
The act or the means of conveying people in mass as opposed to conveyance in individual vehicles carrying very few people at a time.
Radburn layout
The term derives from Radburn, New Jersey, where, over the whole of a small settlement, the arrangements for pedestrian and vehicular circulation were planned as physically independent but related systems. The derivatives are endless and the implications enormous, but the term is probably best confined to the particular type of loop and cul-de-sac planning for residential areas used at Radburn itself.
Regional distributor
See Distributor hierarchy.
Relief road
A term currently used to indicate a road designed to drain off a proportion of traffic from some other road, thereby relieving the congestion.
Reversible lane
A term applied to any road which encircles the centre of a town. Ring roads are usually designated as ‘inner’ (i.e. closely circumscribing the town centre with the object of distributing traffic round the centre and also acting as a town centre by-pass), ‘intermediate’, or ‘outer’.
Saturation level
See Full car ownership.
Screen line

An imaginary line drawn across part of a traffic study area, across which the total number of movements of any particular kind are determined in order to:
(i) check the estimated traffic flows across the same line, or
(ii) give an indication of the road space required across that line.

Severance

As used in this Report, the undesirable division of an area of closely-inter-related uses by a road carrying a heavy traffic flow.

Street

A form of layout consisting of a carriageway for vehicles, flanking pavements for pedestrians, and with frontage development with direct access to premises for pedestrians and occasionally for vehicles.

Tangential road

A term currently used to indicate a road with an alignment approximately tangential to an imaginary circle surrounding the centre of a town.

Through traffic

The traffic in any area whose origin and destination both lie outside the area.

Town traffic

The traffic within a town, city or community, which is associated with the life and activities of the place. It includes vehicles which have come into the locality from outside.

Traffic

The term is extended in this Report to include stationary vehicles as well as moving vehicles.

Traffic architecture

A term we have coined to convey the idea of buildings and the circulation systems which immediately serve them being designed together as a single comprehensive process. At high densities of development this approach produces architectural forms with built-in multi-level circulation systems in which the traditional dividing line between roads and architecture dis-appears.

Traffic-essential and optional

Essential traffic is the business, commercial and industrial traffic which is necessary to service and maintain the life of a community. Optional traffic is the traffic arising from the exercise of a choice to use a vehicle for a journey when the option existed either not to make the journey at all or to make it by some other kind of vehicle or form of transport. Bus traffic may be regarded as essential to the extent that buses are essential to carry loads which for various reasons cannot be discharged by individual cars. There is not necessarily always a very clear distinction between the two. Some apparently essential trips may, upon examination, prove less essential than some optional trips. In addition, if the distinction is made between the two at peak periods, some commercial trips could be called optional, in that they could be made at some other time of day.

Traffic flow diagram

A diagram to indicate quantitatively the volumes of traffic flowing along a road system during some particular period.

Traffic generation

An activity is said to cause or generate traffic when vehicles are used in connection with it. The vehicles may be based at the scene of the activity or they may be regular or occasional visitors. As most activities take place in buildings, it is commonly said that buildings ‘generate traffic’.

Traffic generation factor

A factor related to floor space, number of employees or other significant aspect of an activity, enabling the total number of daily journeys to be estimated for any specific example of activity.

Traffic management

The promotion of the more efficient movement of traffic within a given street system by re-arranging the flows, controlling the intersections, and regulating the times and places for parking.

Transportation plan

A suggested new constituent of the statutory development plan to indicate the way in which the future demand for movement will be shared by the various forms of transport available.

Transportation study

A comprehensive study of all the demands for movement in a locality (including the use of origin and destination surveys, home interview surveys, and other investigations) to provide a basis for a co-ordinated planning of transport systems.

Turnover

The average number of times that a parking space or loading bay is used by different vehicles during a period of 24 hours.

Visual intrusion

The accumulation of vehicles, moving or stationary, within a locality, in a manner detrimental to the appearance of the scene. This includes equipment and development associated with the use of vehicles.