What is PTAL?
PTAL stands for ‘Public Transport Accessibility Level’ and is a measure of connectivity to the public transport network for locations within London.
PTAL values are influenced by the walking distance to nearby stations and stops (inclusive of all bus, tram, National Rail and Light Rail Transit networks), and by the frequency of services at these stations and stops.
Each location is scored a rating from 0 to 6b, with 0 representing the least accessible locations and 6b as an ‘excellent’ standard of accessibility. For example, if an area has a score of 0 it is likely that very limited public transport infrastructure is available. PTAL does not extend to any area outside of Greater London.
The PTAL methodology is considered by TfL as a “best estimate of connectivity based in the information available to us at the time of calculation”.
PTALs can be calculated online using the TfL tool WebCAT (available at www.tfl.gov.uk/info-for/urban-planning-and-construction/). This tool also provides choropleth mapping to provide a visual illustration of public transport accessibility in London.
The PTAL map is spilt in to 100m square grids (i.e. 1 hectare), with the PTAL value calculated at the centre of the square. The mapping can therefore be quite crude in certain locations.
Once a location is selected on the PTAL map, it is possible to download the output containing either the mapping or PTAL calculation report in isolation, or a full report including all calculations.
When generating reports, it is possible to select data to represent the baseline (current) year, or a projected forecast for 2021 or 2031 which incorporates planned public transport improvements such as underground line exetnsions.
PTAL is a tool to be applied to new developments in order to determine the required level of parking provision as laid out in the London Plan. For example, a development with a higher level of accessibility to the public transport network will generate a reduced demand for car parking spaces.
Calculation Factors Affecting PTAL
The thresholds in the PTAL model work on 640m walk to a bus stop (8 mins) and a 960m walk to a rail/tube station (12 mins).
A location will have a higher PTAL if:
• It is a short walking distance to the nearest stations or stops;
• Waiting times at the nearest stations or stops are short;
• Higher frequency of services call at the nearest stations or stops;
• Reliability of service / mode is high;
• There are major rail stations nearby.
There are however limitations to the PTAL methodology and a range of other factors that need to be considered which are not necessarily identified by the PTAL assessment.
Limitations of PTAL
Public transport nodes which are just outside the thresholds are not accounted for, even if they’re a mere 10m outside of the area for example.
PTAL is a quantitative measure of public transport accessibility and does not include a qualitative assessment which might consider equally applicable factors, as set out below.
A PTAL rating of 6b is generally reserved for locations within Central London which benefit from a high density of tube stations and bus stops nearby but does not asses how busy a particular route is and the capacity of public transport modes.
Any planned transport infrastructure developments such as Crossrail will significantly affect the future PTAL rating and are sometimes included in 2021 / 2031 outputs.
Night buses and all night underground services are not included in the calculations since the standard PTAL assessment period is 8:15-9:15am
The WebCAT tool is crude in that it applies to 1 hectare squares and may not be applicable to the development if it is located on the edge of the square for instance. RGP in this instance can assess the situation to create calculations specific for your site.
Understanding Other Factors
There are other key factors that could influence the accessibility of a specific location which are not calculated by the PTAL tool. Some of these considerations include;
– The quality of waiting facilities and the provision of real-time information
– Attractiveness of destinations served by routes
– Availability of public transport nodes beyond the threshold distances
– The proximity to shops, schools, employment destinations and healthcare facilities, which can reduce the need to travel. This can be further investigated using the ATOS measurement which provides an indication of ‘Access to Opportunities and Services’ as defined in the London Plan
– The quality of walking routes and crossings between the site and local public transport infrastructure
– Safety conditions locally
– Cycle infrastructure
– Car clubs and other sustainable transport infrastructure.
PTAL and Parking
Parking standards applied in Greater London are detailed within the London Plan (March 2016)
The London Plan uses PTAL as an indication of the level of parking provision a development should support. Depending on the PTAL rating of a location in London, the London Plan outlines specifications for the level and type of parking provision required for a proposed development.
The PTAL rating does not affect the requirement for disabled parking spaces that must be provided for a site.
The London Plan also defines parking standards in context of provision for electric vehicles at new developments. Further reading regarding electric vehicles can be found in RGP’s ‘Electric Vehicle Charging Points, a Summary Guide for Developers’ Technical information note (available at http:///news/electric-vehicle-charging-points/).
The required amount of spaces for a development is calculated in the London Plan based on two factors; its PTAL rating and its proposed use.
Sites with higher accessibility to public transport (defined as PTAL 4 or above) require the least amount of parking, for sites with PTAL 5 or above, zero parking is supported by the London Plan (March 2016).
Planned improvements to public transport will increase accessibility throughout London. Therefore, future PTAL assessments maybe an important consideration and may assist in negotiations, since by the time your development has been completed the PTAL will be higher due to public transport infrastructure improvements.
What RGP Do
RGP can assess baseline data to find site specific PTAL ratings, but also assess those factors which are important to determining the parking provision or appropriateness of a development. This information would be used to formulate arguments for negotiations to support your scheme.
Please call our Godalming or London offices to speak to a consultant who would be pleased to discuss your project on 01483 861681 (Godalming) or 020 7078 9662 (London).