Our field of expertise involves a large amount of technical terminology. See below to find out more about frequently used abbreviations. If there are other terms you haven’t heard of, contact us to find out more:


Annual Average Daily Traffic (AADT) flows are used by Air Quality Consultants in their Assessments to establish the impact of a development on local air quality. These are typically carried out for larger developments or in sensitive areas such as Air Quality Management Areas (AQMA’s). AADT flows are the average traffic flows recorded across 365 days.


Annual Average Weekday Traffic (AAWT) flows are used by Noise Consultants to establish the impact of a development on local receptors. AAWT flows are the average traffic flows taken over five days, Monday to Friday.

Interim TP

An Interim Travel Plan is usually prepared to accompany a planning application where the end user is unknown. A full Travel Plan will usually be a condition of planning permission if the application is approved and the interim travel plan can be adapted to suit the end user.  A full Travel Plan would require a traffic survey of the site users immediately after occupation to set a baseline journey model and allow accurate targets to be set.

Framework TP

A Framework Travel Plan is prepared where there are numerous end users for the development such as a mixed-use development with retail, leisure and restaurant uses, for example.

S106 Agreements

Planning obligations under Section 106 of the Town and Country Planning Act 1990 (as amended), commonly known as s106 agreements, are a mechanism which make a development proposal acceptable in planning terms, that would not otherwise be acceptable. They are focused on site specific mitigation of the impact of development. S106 agreements are also known as developer contributions and can include for transport and highway improvements.

S278 Agreements

A  Section 278 Agreement is entered into with the Local Highway Authority where a development requires works to be carried out within the existing public highway.  These works could include the construction of a new access or junction improvements. Highway Authorities may provide the works at the developer’s expense, or may allow the developer to provide the works directly. A bond may be required to ensure that the work is completed to a satisfactory standard.

S104 Agreements

A Section 104 Agreement is a section within the Water Industry Act 1991 which permits the adoption of a sewer, lateral drain or sewage disposal works by a sewerage undertaker.  Before adoption can take place there is a period of maintenance which varies between companies, before the sewerage undertaker adopts the sewers and becomes responsible for their repair.

S38 Agreements

A Section 38 Agreement (Highways Act 1980) is the usual method whereby highways provided by a developer may become maintainable at the public expense (formally adopted as public highway). Generally residents on a new development will benefit from adoption of new roads and footways and street lighting as the Highway Authority become responsible for  maintenance issues. Formal adoption generally takes place after a 12 month maintenance period and once the Highway Authority have carried out an inspection to sign off the works.

Multi-modal trips

Rather than referring only to vehicular trips, our assessments usually include multi-modal trips which will include the predicted trips from a development on foot, cycle and public transport.

Passenger Car Unit (PCU)

A Passenger Car Unit (PCU) is a method used in Transport Modelling to allow for the different vehicle types within a traffic flow group to be assessed in a consistent manner.

Typical factors are 1 for a car or light goods vehicle, 2 for a bus of heavy goods vehicle, 0.4 for a motorcycle and 0.2 for a pedal cycle.


Ratio of Flow to Capacity (RFC) is a term used in Transport Modelling to assess the operation of a junction.  Sometimes known as Reference Flow to Capacity ratio, the result provides an indication of likely junction performance, with a value of 1 implying that the demand flow is equal to the capacity.  Typically a value of 0.85 is seen as the practical capacity, with results higher than this more likely to experience queuing or delay.