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Transport Impact Assessment

Traffic has many impacts, it creates noise, pollution and roads can be visually unattractive.

Management of these and other impacts may require mitigative measures to the intended development, for example the location of the development will affect the distance people travel to get there.

Modal shift should also be considered, how can people be encouraged to get on their bicycle, or on to a bus.

A major part of any traffic impact assessment will be a travel plan and and transport assessment, which are now common place for larger development as per governments sustainability initiatives.

As of 2014, thresholds for Transport Statements and Transport Assessments are not in place, and it is at the determining authorities discretion as to whether they deem a Transport Assessment or Transport Statement necessary based on whether the development is "significant".
traffic impact 

Traffic / Transport Assessment Links

Transport Statement   Transport Assessment   Junction Capacities
         
Predicting Trip Numbers   Wider Transport Area   PICADY and ACARDY Assessment
         
Road Capacity        
         

 

In recent years we have moved away from the building of new roads to the encouraging of using various forms of transport, since the mid 90's government has decided that catering for more cars, actual creates more trips, and so this new sustainable approach to lessening impact has been adopted.

Transport Statement

For smaller developments of for development not expected to create high traffic volumes (for example data centers). A "overview" level transport statement may be required at the planning stage.

These reports are typically factual, with perhaps a small degree of interpretation describing trip generation and and how this relates to current levels experienced on the roads adjacent to site.

A transport statement will likely require a baseline study.

Transport Assessment

The thresholds that have officially been abandoned in 2014, are none the less still in many cases used  as a bench mark for when an assessment may be required. If you development has over 80 houses (C3) or 100 bedrooms (C1). Then you can expect to have to provide a Transport Assessment. A transport assessment will likely require a baseline study.

A transport assessment will require a great deal of detail on not only the immediate area but an assessment of the surrounding road network, sometime covering many junctions over a considerable radius. Why?

 

Junction Capacities

A junction capacity can be determined quite simply for small sites with low transport burdens, however for larger site an assessment of junctions will require use of a computer assessment tool such as ARCADY or PICADY.

 

Road Capacity

Road capacity can be determined in a number of ways. Unless we consider the scheme to be particularly high impact we would start with the most basic and cost effective method for assessing road capacity.

Computer modeling can be used, but other analog methods are often successful.

Many roads are over capacity particularly those in a historic setting, such as cross roads in settlement centers. In such cases it may be necessary to undertake a detailed study of such junctions, in order to derive saturation figures.   Saturation figures over 100% will require that the junction is improved or that other measures are taken to lower the transport junction on the junction.

Wider Transport Area

A baseline study or survey can be used to make an assessment of current traffic volumes and behavior in the study area. Secondary data is available for the wider transport network, if the road are major, however for smaller sites this is often not the case.

Predicting Trip Numbers

Many development times have published multiplication factors, where by generated traffic can be calculated using

PICADY and ACARDY Assessment

ARCADY includes a unique set of tools to help with the measurement of standard and mini-roundabout geometries such as entry width, flare length and entry radius.

ARCADY 9 can model: Roundabouts, Mini Roundabouts, Linked Roundabout Networks, Large or Grade Separated Roundabouts & Pedestrian Crossings (Signalled, Unsignalled and Adaptive)

PICADY is the other module in Junctions and is used for modelling priority-controlled junctions such as crossroads and T-junctions. PICADY 9 sees the implementation of additional models applicable to North America and allows users to setup and model Two-Way Stop Controlled (TWSC) and All-Way Stop Controlled (AWSC) intersections

  

A Transport Assessment is a comprehensive and systematic process that sets out transport issues relating to a proposed development, identifying what measures must be taken in order to deal with predicted traffic impacts of the proposal. As a result accessibility, and safety for all modes of transport.

There are three main under pinning factors considered in a transport assessment;

Encouraging Sustainable Transport Access

This is achieved by reducing the need for travel. The private car is public enemy number one here.

M5 bristol somerset

Transport Assessment Further Reading:

Thresholds for Transport Assessment   Minimum Road Widths   Types of Transport Base Line Study
         
Method for Transport Assessment Surveys        

 

Managing the existing Transport framework.

Efficiency of existing public transport networks can be improved via the implementation of efficiency measures. For example better time tabling on bus routes.

Mitigating Residual Transport Impacts

 

The use of sustainable transport options should be considered when designing the development, i.e. there should be consideration for pedestrian and cyclists.

Do I need a Transport Assessment?

Thresholds for developments have been established (these have been officialy withdrawn, but are still used by many planning authorities):

Land Use Unit Threshold
Hospital beds 50
Dwelling Units units 80
Offices floor area msq 2500
General Industry floor area msq 4000
Retail floor area msq 8000
Cinema and Other Leisure floor area msq 1500

We at SWEL are always happy to discuss any question you may have regarding transport assessments so please ring / email us.

Transport Base Line Studies

- Base Line Transport Assessment

- Public Transport Assessment

- Walking and Cycling Assessment

- Road Network Assessment

- Traffic Data and Traffic Forecast

- Accident Analysis

modes_of_transport

Minimum Widths for Various Roadways

Published in The "Design Manual for Roads and Bridges" here are the minimum widths for various types of roadway;

Footway

Dimensions
2.00m Standard Width
3.00m including Cycle Lane
Materials
Urban : Flagstones / Bituminous

Carriageway (Dual)

Dimensions
7.30m Standard Width (3.65m Lanes)
8.80m including Cycle Lane
8.80m including No Car Lane
Materials
Bituminous : All Locations

Verge

Dimensions
2.00m Minimum Width
Materials
Urban : Hard / Soft Landscape
Residential : Hard / Soft Landscape
Industrial : Soft Landscape
Rural : Soft Landscape

Central Reserve

Dimensions
3.00m Minimum Width
Materials
Urban : Hard / Soft Landscape
Residential : Hard / Soft Landscape
Industrial : Soft Landscape
Rural : Soft Landscape

Cycle Lanes / Cycle Routes

Dimensions
1.50m Minimum Width (On-Street Lane)
3.50m Minimum Width (Segregated Route)
3.00m Minimum Width (Shared Route)
Materials
To Match Footway or Carriageway

Transport Assessment Gallery

Please click on any of the below Transport Assessment Related images to enlarge them.

 

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