Measuring Public Transport Accessibility

Measuring Public Transport Accessibility


A Poole, Halcrow Group Ltd., UK Public transport in small towns - an area with great potential



1. Introduction

This paper sets out a review of issues connected with measuring accessibility, particularly in appraisal of transport or development schemes. Accessibility in this context is taken to mean ease of access to transport in order to reach key destinations and services. This is an area that has assumed greater importance in overall policy making in recent years; indeed, the UK Department for Transport (DfT) announced recently that a working group would be set up to develop good practice guidance on monitoring accessibility to key services.

However, accessibility does not lend itself easily to quantification, and perhaps for this reason it can tend to be given a low importance in decision making. There is therefore a need to ensure that the issues are better understood, and that techniques used in appraisal are simple to use, correspond well to reality and are capable of measuring change

The paper draws largely on work carried out as part of a major research project for the UK Highways Agency (HA), examining existing guidance on accessibility appraisal in terms of effectiveness and practicality. The work was carried out with the support of sub-consultants Social Research Associates. Staff from the UK Department for Transport (DfT) were also closely involved in this project.

2. Existing Guidance

Traditionally, scheme appraisal in the UK has tended to focus on safety and journey time impacts, and to a certain extent environmental issues. However, current UK guidance on appraisal also includes a category of Accessibility, which is intended to pick up wider issues of social inclusion, access to services and general community impacts. Within this topic area, a key issue is the measurement of ?Access to Transport?.

Various bodies have developed criteria in an attempt to quantify this, for use in development planning and transport scheme appraisal, or simply trying to measure how ?well connected? an existing community is. Usually, criteria are specified such that a public transport service of a given standard (e.g. hourly) should lie within a certain maximum distance of any household. Some examples are as follows:

* the DfT define a ?core indicator? that all English Local Authorities are required to measure, namely ?the proportion of people in rural areas living within a 13 minute walk of an hourly or better bus service?.

* for new transport schemes, guidance in the DfT?s Guidance on the Methodology for Multi-Modal Studies (GOMMMS) defines an indicator A that measures access to both private and public transport. It equates to the proportion of households within a given study area that have either a car available, or are within 250m of a ?daytime hourly? public transport service.

* various local and regional bodies in England have attempted to define more sophisticated measures of accessibility, for example making a distinction between bus and rail services and including factors such as topography.

3. Methodology

For the research carried out for the HA, a series of case study sites were chosen across the UK, aimed at demonstrating a variety of different issues (such as urban/rural context, new/unimproved roads, high/low public transport provision etc). For each site, the following activities were carried out:

* a review of key data such as flows, accidents and public transport provision in addition to general observations

* social research, including discussion groups and questionnaire interviews

* application of existing methodologies to the local situation, in order to highlight any practical issues arising and to try to correlate the answers obtained with the perceptions and reality ?on the ground?.

4. Key Issues with Existing Methodologies

In terms of the practicality of existing appraisal methodology, key issues were as follows:

* there are difficulties in defining and measuring what constitutes and acceptable level of service. For example, reference is often made simply to a ?daytime hourly? bus service, with no account taken of destinations served or the quality of journey, which both emerged as key factors in providing useful access to services. Such a definition is also insensitive to any changes in public transport provision other than those that specifically introduce a new service, or improve an existing less-than-hourly service.

* calculation of the population living within a defined distance of a public transport service is not straightforward. While recent developments in GIS (Geographical Information Systems) assist in this process it can still be inaccurate and time-consuming. Furthermore, it could be argued that time, rather than distance, is of more relevance as a short distance on a map may correspond to a time consuming journey crossing busy roads.

* the GOMMMS methodology implies that any household with one car or more has full ?access to transport?. However, in one car households in particular, this is not necessarily a realistic assumption, and social exclusion can still occur if the car is unavailable to most householders for most of the day. A ?car-weighted? methodology was considered that would help to take account of this factor.

* the value obtained for the GOMMMS Access to Transport indicator A under a variety of existing situations varied from a worst case of 85% to just under 100%, and is rather insensitive to change. As such, appraisal of a new scheme by this methodology would rarely result in anything more than a ?slight change? assessment. One of the reasons for this is the mixing of access to private and public transport within a single indicator.

5. Key Attitudinal Issues

The case studies also raised a number of interesting issues in terms of people?s attitudes. It was found that some of worst problems in terms of access to services were found in prosperous areas. The public transport provision tended to be poorer in these locations, and for the (relatively small) number of people without a car, social exclusion was particularly high. Furthermore, even where an hourly bus service existed it often failed to provide ?there and back? access to nearby jobs for a typical working day. For the increasing number of people working to ?untypical? hours, alternatives to car use were even more limited.

Of particular interest was the way in which many households that had recently purchased a car re-focused their lifestyles to such an extent that use of public transport was no longer considered, even when the car was temporarily unavailable (such as for repairs). In these circumstances people would often borrow or hire a car, or seek a lift. In a sense, the public transport habit had been ?lost? and was hard to regain. Conversely, a number of people used cars but only reluctantly ? many women in particular disliked driving on busy roads or at night and would have welcomed better alternatives.

Another factor is ease of movement within the local community. A number of the locations considered suffered from community severance, which affected people?s willingness to travel on foot and general quality of life. In this respect, a bus service may be close by but not particularly easy to access. Conversely, rural settlements that straddled main routes often tended to have more frequent public transport services than those that had been bypassed. Interestingly, the level of severance experienced often depended more on issues of detail, such as the design of a new road or narrowness of footways, than on vehicle speeds and volumes.

6. Summary and Conclusions

Recent guidance on scheme appraisal in the UK has attempted to include ?accessibility? impacts in more detail, to be considered alongside aspects such as safety and congestion. However, the methodologies currently used have certain limitations and the issue still tends to be somewhat marginalised in decision making. People?s attitudes and responses to change are also complex and require further investigation. However, the work carried out to date has highlighted various techniques that could be used now to improve existing appraisal processes, and help to ensure that greater weight is given to this area in future.


Association for European Transport