Measuring the Accessibility of Opportunities and Services in Dense Urban Environments: Experiences from London
P Wright, S Cooper, R Ball, Transport for London, UK
A new measure of Access To Opportunities and Services (ATOS) has been developed for London.
The experiences of developing a measure of accessibility for a high density city such as London provide a practical tool for other European cities.
Currently accessibility in London is measured by PTALs (Public Transport Accessibility Level). The PTAL score is a measure of access to the public transport network combining walk time to the network with service waiting time at the stop/station for any location in London. The score will be influenced by the:
- number of stops / stations within the defined catchment area
- proximity of these stops / stations
- the number of routes served at each stop / station
- the frequency of services
PTALs help to identify where Londoners have poor or good access to the public transport network. However PTALs do not take into account:
- Where the public transport goes
- What services can be accessed
As part of the cross-Government strategy to improve to the services with greatest impact on life opportunity, the Department for Transport (DfT) has developed core accessibility indicators for the whole of England, which look at the quality of access to key services. Local authorities outside London are required to set a target for at least one local accessibility indicator as part of their Local Transport Plan. They can use the DfT¡¦s indicators, yet they are also encouraged to develop their own indicators to reflect local priorities. In the case of Greater London, local authorities are not obligated to report on accessibility as Transport for London (TfL) is accountable for ensuring good quality access. However a measure tailored for London is required for meaningful analysis, taking into account London¡¦s characteristics and the Mayor of London¡¦s priorities.
A new measure of Access to Opportunities and Services (ATOS) has been developed by TfL and is currently being tested with a sample of local authorities. ATOS measure the level of access to employment, education, health services, quality food shopping and open spaces.
- Employment: average journey time to the nearest 10,000 low qualified and high qualified jobs
- Education: average journey time to the nearest 3 primary schools, secondary schools and further education colleges
- Health: average journey time to the nearest 3 GP surgeries
- Quality food shopping: journey time to the nearest town centre or supermarket
- Open spaces: walking time to the nearest publicly accessible open space
In order to take account of the high density of population and services in London the ATOS measure reflects a degree of choice and measures accessibility by different modes. Journey times are calculated based on public transport and /or walking modes using TfL¡¦s CAPITAL model. Times can also be calculated for walking and cycling modes individually. Results are calculated at Census Super Output Area level and supplemented by Census Output Areas in the more rural areas of London to provide a greater degree of granularity (a total of approximately 5,200 origin points).
ATOS provides a measure of the current level of accessibility to each service and can be used to identify areas which either require improvements in transport provision and / or investment in the level of each service provided. The use of TfL¡¦s CAPITAL model also provides the ability to measure the impact on the level of accessibility of proposed transport infrastructure improvements.
Initial results suggest that whilst areas with high levels of PTAL are likely to have high ATOS scores, some areas of London with poor levels of access to public transport still have high levels of access to opportunities and services. This allows investment to be prioritised to meet local needs, e.g. investments in walking and cycling may be most appropriate in areas with low PTAL scores.
The experiences of developing a measure of accessibility for a high density world city such as London provide a practical and useful tool for other European cities. ATOS will help promote improvements in social inclusion by identifying the best locations for investment in both transport and service provision. Finally it will also provide an excellent assessment of the effectiveness of new investments in either transport or land use.
Association for European Transport