Transport Scotland's highway economic appraisal system, NESA

. . . documentation downloads

NESA ocupies Vol 15 of DMRB, written by SIAS

SIAS has maintained, developed and distributed NESA on behalf of Transport Scotland and its predecessors since 1978.

Click on the following links to download the most recent NESA documentation in pdf format:

Document NESA version Date File size

NESA Manual p05.01.11 July 2005 2.931mb

Interim Guidance p05.01.11 July 2005 39kb

Readme p05.01.11 July 2005 10kb

Functionality p05.01.11 July 2005 57kb

It is recommended that you download the latest version of the manual.

NESA clients can obtain technical support by sending an email to nesa-support@sias.com.

The analysis of traffic flow on urban motorways poses a special challenge because of the potential interaction with non-motorway surface streets, and the increasing requirement for an understanding of the viability of ramp control systems. SIAS is well placed to practise in this area, because of its extensive understanding of microsimulation and urban traffic control systems.

SIAS continues to undertake NESA commissions. See elsewhere on this site.

NESA: What is it?

Although sometimes regarded as the Scottish version of the DFT's trunk-road cost-benefit analysis software COBA, NESA has a wider scope and operational remit. NESA is a full suite of transportation modelling software, and was designed by SIAS in 1978 to a Scottish Office brief which resulted from concern that COBA did not fully address the conditions encountered within a Scottish trunk road context.

COBA is commonly used following an analysis using other traffic modelling software, required for matrix building and trip assignment. With the exception of trip generation, NESA was designed to undertake most of the functions familiar to transportation modellers, and was particularly well suited for operational and economic assessment of simple schemes and small town bypasses. In comparison to COBA, the integration of modelling and economic assessment components not only makes NESA easier to use but also avoids a number of inherent complexities and approximations associated with COBA. Following several revisions, SIAS still holds a commission from Transport Scotland for the development and maintenance of NESA.

NESA remains one of Transport Scotland's key tools for use in the operational and economic assessment of non-complex trunk road schemes. In the case of significant software updates, the commission has involved the supervision of beta test sites at up to four engineering consultants' premises. NESA has been incorporated within the DETR's Design Manual for Roads and Bridges, written by SIAS as Volume 15.

The current version of NESA, which reflects the principles and parameters outlined in TAG Unit 3.5, incorporates several significant developments including enhanced procedures for the assessment of accident savings, simulating traffic flow variations throughout the year, and interfacing the economic assessment module to other modelling suites.

SIAS distributes NESA free on request, and provides user support. Since 1980, SIAS has undertaken more commissions requiring NESA than any other organisation. SIAS's unique understanding of the flexibility and application of NESA has ensured successful highway scheme implementations throughout Scotland.