As I was going through the new London Plan yesterday I noticed a number of references to PTAL. I didn’t know what this was, so I obviously had to look it up.
It stands for Public Transit Accessibility Level. It’s a methodology that was developed in London in the 90′s. And it’s a measure of access to public transit, or of the density of the public transport network at any given location.
There are 6 levels, though two of the levels are further subdivided into 2 sub-levels for greater precision:
- 1a and 1b
- 6a and 6b
1 is bad. 6 is good.
What’s captured in this measure are the walking times from a particular location to the nearest transit access points; the reliability of the available services; the number of services available; and the average wait times.
Historically, this measure has helped to determine how much density could be built on a particular site, how much parking should be provided, and so on.
For example, in the new London Plan, PTAL 5 and 6, as well as Inner London PTAL 4, are expected to see development with no residential parking. Once you move to PTAL 3, the parking maximum moves up to 0.25 spaces per unit.
In the draft London Plan you’re also supposed to use the highest existing or planned PTAL. So if transit improvements are planned for the area, you factor those into the calculation.
Seems quite rationale (though it’s probably not a perfect measure of access and connectivity).
If you’d like to determine the PTAL for a particular address in Greater London, you can do that here. Unfortunately, I don’t have a calculator for you if you happen to live outside of London. But there is one simple check you can do.
The PTAL methodology assumes an average walking speed of 4.8 kph. The maximum allowable walk time for buses is 8 minutes and the maximum walk time for subway and light rail is 12 minutes. These numbers translate into distances of 640m and 960m, respectively.
How far do you have to walk to access good transit?