Summary Report

1. Introduction

Background to the Study

For the past half century the development of the City of Cambridge and surrounding areas has been severely constrained. The Holford Report of 1950 proposed to limit the development of the City and surrounding villages. It was recommended that Cambridge should be limited to 100,000 people. This figure was just about maintained (108,000 in 2001) as a result of restricting housing development and a strong green belt policy. Employment, especially manufacturing, was encouraged to locate or relocate elsewhere in the region.

By 1969 the constraints on employment growth were relaxed following the Mott Report (1969) that allowed science and university based industries to be located in the city. This opened the way for the Trinity Science Park and similar employment clusters, which led to the birth of the Cambridge Phenomenon: there was a surge of growth of high-tech firms and associated services, employing over 23,000 people. Today, this forms the backbone of the Sub-region’s successful knowledge based economy.

The contradictory nature of the policies that allowed employment to grow but constrained the growth of housing has had serious consequences: house prices have risen substantially. It has been necessary for increasing numbers of people who work in Cambridge to live beyond the green belt, where cheaper housing more than offsets the cost of travel into Cambridge. Medium and lower income groups have been displaced because they can no longer afford property prices in Cambridge unless protected by social housing.

The population growth in surrounding villages and market towns has been amongst the highest in the country. As a result there is a daily influx of workers from outside the City: this outnumbers the resident workers. Traffic congestion has grown as a result of more people commuting by car, causing delays, accidents and pollution: their dispersed origins mean that public transport is unviable for many of these journeys.

The continued success of the Cambridge Sub-region in now under threat. Segal Quince Wickstead have reported that difficulties in recruitment and shortages of available premises are the major threats to future economic growth in the Sub-region. Recruitment is not helped by increased housing and transport costs faced by incomers.

In order to maintain and improve the economic opportunities for Cambridge as well as increasing the social equity of the area while protecting the environment, the Regional Planning Guidance advocated a change in the policies, alleviating the constraints on the development of the Cambridge Sub-region. New housing should be located where the jobs are: in the City, and subject to a review of the green belt, by extending the city. New housing, beyond green belt, should be located in a new settlement and in the market towns and large villages. The recommendations of the Regional Planning Guidance have been taken further in the Revision of the Structure Plan of Cambridgeshire and Peterborough.

The removal of the 50 year constraints on the size of Cambridge should increase the population of the built up area of Cambridge by one third from 1999 to 2016. Due to the increase of households and employment, the size of the urban area will expand into the green belt with more people travelling within the built up area.


The Options

The Base Case assumes the full implementation of the land use policies in the Structure Plan 2003 and the committed transport improvements. It represents the most likely land use scenario to become reality. The options represent the Base Case plus further transport measures. Each show what could be achieved by focusing entirely on a single transport instrument. These include non-motorised modes of transport (cycling and walking), public transport, road building (in the form of an orbital highway), and demand management (represented by congestion charging). This aims to show what each approach can achieve independently. There is also a Combined Option that examines how all four of the options would work together.

The options are broadly consistent with the transport policies in the Structure Plan, which promote cycling, walking and high quality public transport, and recognise the need to cater for orbital movements, and provide demand management.

Simulation Models

Following the first Cambridge Futures (1999) study, the same computer simulation models (MENTOR/SATURN) have been used for forecasting and assessing the likely outcomes of alternative options. These models have been used by Cambridgeshire County Council to test the Structure Plan policies. This represents the Base Case against which this study compares the options.

Cambridge Futures has added transport elements to this base simulation model to represent each of the options. As illustrated in the figure above, the models simulate the working of two inter-related markets: the land market and the transport market.

The year 2001 constitutes the base year for comparisons between future scenarios and existing conditions; the model has then been run at 5 year periods (i.e. 2006, 2911, 2016 and 2021). This base run represents the implementation of the Cambridgeshire Structure Plan policies and provides the bench mark against which the other options have been compared, with transport assessment for years 20901 and 2016. The majority of the outputs are illustrated for the year 2016 – the final year of the Structure Plan.


The assessment of the options is performed in two ways: feasibility and sustainability. Feasibility assessment tries to determine to what extent the options are viable, not only technically but economically. It uses cost benefit analysis, as recommended by the Treasury for public funding of infrastructural projects (HM Treasury, 2003), to compare the capital costs of implementing the options with the benefits generated by the options. The benefits, measured in monetary terms, are calculated for users of the transport system, to estimate the rate of return on the investment. There are two rates: social and private. The social rate includes all valued benefits to society, while the private rate includes only the benefits accruing to the investor in the transport system.

From a sustainability point of view, the options are assessed in terms of:

  • Economic efficiency: this considers the economic impact of the option measured by changes in prices, for consumers (households) and producers (mainly exporters). This form of appraisal is more comprehensive than the standard cost-benefit analysis used in transport assessment (as calculated in the feasibility assessment above), as it not only measures the benefits to transport users, but to the economy as a whole.
  • Social equity: this considers the distributional impact of the options – the cost and benefits for different socio economic groups. It also considers the spatial segregation of socio economic groups.
  • Environmental impact. This uses energy consumption as a measure of the impact of the global environment. Lower fuel consumption represents less use of unrenewable energy and lower carbon emissions, which are thought to contribute to climate change. The SATURN traffic model produces estimates of overall fuel consumption by traffic for the Sub-region. This partly depends on total distance travelled by also on the amount of traffic congestion. Engines are less efficient when accelerating and decelerating.
    Local air pollution is also related to the amount of traffic and is make worse by congestion. Local environmental effects have been assessed on the basis of professional judgement rather than surveys and calculation. Noise from vehicles is related to a number of factors, particularly the volume of traffic, distance of properties. Other significant local effects include visual intrusion on the landscape, and the effect on the townscape.

The comparison of the options includes an Appraisal Summary Table that compares the options against the Base Case using the impacts recommended in the Guidance for Multi-Modal Studies.

Introducing the Study Base
Cycling/ Walking Public Transport Orbital Highway Congestion Charging Combined Option Options Compared